Astrophotography

Image Credits: Joe Haberthier, Dave Morgan, Steve Childers, and Bruce Gavett

Astrophotography is a fascinating area. The night sky is full of great deep-sky objects to image and bring to life. The downside is that this isn’t one of the easiest things to do. It is dark out at night and most objects are very far away. In addition, the Earth rotates, making it difficult to track objects and capture long exposures. As such, astrophotography can be a rather complicated and expensive hobby.

For a start, see the Introduction below to get your started. You can also check out our Astrophotography Basics page before diving into too much of the details. In addition, you will find, rather quickly, that taking the images is just a start. There is also a great deal to understand about how to process your images.

Despite the challenges, several FAS members are quite good at this and you can find samples of their images and links to their photo galleries on our FAS Members Astrophotography page.

On This Page

Basic Information

Other Information

Image Processing

Image Processing Software

An Introduction To Astrophotography

In general, astrophotography is all about photographing the night sky. There are generally three different levels to this. You can photograph the night sky itself (landscape astrophotography), focus on the Moon and individual planets (planetary astrophotography), or go after deep sky objects such as nebulae and galaxies (deep sky astrophotography). Most choose the latter.

There are several smart telescopes, particularly the relatively inexpensive Seestar S30 and S50 along with the Dwarf 3 and Mini, that are on the market. This might be a good starting point. These telescopes handle much of the complexity of astrophotography and provide a good introduction to the area. See our Smart Telescope Basic page for an introduction to this. See our smart telescopes section for more about what is available on the market.

Another option is to use a DSLR camera along with a star tracker or an equatorial tracking mount.

A more complicated, but possibly more rewarding approach is to utilize a full astrophotography setup. See our Introduction to Astrophotography for an overview. However, at the most basic, you will need: An imaging Telescope & Camera, an auto-guiding Telescope & Camera, a Mount, and a Tripod. An Electronic Auto Focuser (EAF) and Filters are also helpful. Of course, you will need a Power Station to run all the equipment.

You can add a computerized controller such as ZWO’s ASiair, which makes the entire process much easier and something you can control from your smart phone or tablet. ZWO has also introduced two Smart Cameras that combine the ASiair functionality with a camera to provide guiding, imaging, and control in one package.

Please note that FAS does not specifically recommend or endorse any specific telescope or setup, we only provide information that is generally available.

Additional Resources (Introduction to Astrophotography using a DSL camera)

Additional Resources (Introduction to Astrophotography)

Additional Resources (Astrophotography Guides)

Additional Resources (Astrophotography Equipment)

Additional Resources (Astrophotography YouTube Channels)

Additional Resources (Deep-Sky Objects)

Astrophotography with your smartphone

One of the long-time members of FAS gave a presentation on how to capture images with your smartphone. Here are several resources from his presentation along with a few more.

Image Credits: Sean Wood.

Smart Telescopes for Astrophotography

Astrophotography used to be the domain of the more experienced amateur astronomer. However, there are now several options even a beginner can use.

The ZWO Seestar S50 is becoming popular with several club members. ZWO has also introduced the Seestar S30 and Seestar S30 Pro, smaller versions of the S50. For more information, see the ZWO website or our Seestar Telescopes webpage. The Dwarf III and Dwarf Mini from Dwarf Labs are inexpensive alternatives to the Seestar.

Seestar S50 Image Credits: Bruce Gavett.

Currently, there are several smart telescope choices out in the marketplace.

Smart Telescopes

  • Dwarf Labs.
    • Dwarf Mini (Dwarf Labs). At around 1.8 lb., this new offering, priced at $400, is advertised as the first pocket smart telescope.
    • Dwarf III (Dwarf Labs). At just under 3 lb., this is a low priced ($550) alternative to the ZWO Seestar with a 35 mm aperture, 150 mm focal length, and 8.3 MP (2 um pixel size) camera.
  • ZWO.
    • Seestar S30 (ZWO). At around 3.5 lb., this is a smaller alternative to the ZWO Seestar S50 and the Dwarf 3.
    • Seestar S50 (ZWO). It is around 5 1/2 lb., priced at $550 with a 2 MP camera, 50 mm aperture, and 250 mm focal length.
    • Seestar S30 Pro (ZWO). Just launched (January 2026) with quadruplet optics, enhanced 8 mp sensor, and nightscape mode. For more on this, see our recent post about the Seestar S30 Pro.
  • Spectrum Optical Instruments: SPi53 Smart Telescope. More to come …
  • Vaonis: It is around 11 lb. and has a 50 mm aperture and 250 mm focal length.
    • Vespera II. It has a 8.3 MP camera (2.9 um pixel size) and is priced around $1,700.
    • Vespera Pro. It has a 12.5 MP (2 um pixel size) camera and is priced at $3,000.
  • Unistellar.
    • Odyssey It is 8.8 lb. with a 5 hour battery life, an 85 mm (3 1/3”) aperture, 320 mm focal length, and 3.4 & 4.1 MP (1.45 um pixel size) camera. It has an autofocus and does not require collimation.
      • Odyssey Base model comes without an eyepiece and is priced at $2,300.
      • Odyssey Pro model comes with an eyepiece and is priced at $4,000.
    • Expert Range. It is 15.5 lb. with a 114 mm (4 1/2”) aperture, 450 mm focal length, 2.9 um pixel size camera. It has a manual focus and does require collimation.
      • eQuinox 2 comes without an eyepiece, 6.2 MP camera, 11 hour battery life, and is priced at $2,500.
      • eVscope 2 comes with an eyepiece, 7.7 MP camera, 9 hour battery life, and is priced at $4,900.
  • Celestron: Origin Intelligent Home Observatory Mark II. This is Celestron’s high end 6” smart telescope. The total system weighs over 41 lb. It has a 152 mm aperture, 335 mm focal length, 6.4 MP (2.4 um pixel size) camera, and is priced around $4,300.
TelescopeWeightPriceAperture (mm)Focal RatioFocal Length (mm)Camera (MP)Note
Dwarf Mini1.85 lb.$40030 (1.2”)1502.1
Dwarf III3 lb.$55035 (1.4”)f/4.291508.3Telephoto & wide angle lenses
ZWO Seestar S303.5 lb.$40030 (1.2”)f/5150IMX662 (2.1)Telephoto & wide angle lenses. Now with EQ mode.
ZWO Seestar S505.5 lb.$55050 (2”)f/5250IMX462 (2.1)Portrait mode – now with a Mosaic option & EQ mode.
ZWO Seestar S30 Pro 3.5 lb.$60030 (1.2”)f/5.3159IMX585 4K (8.0)Wider field of view with a better sensor and improved optics. Nightscape mode.
SPi53 Smart Telescope6.1 lb.$700More to come …
Vespera II & Pro11 lb.$1,700 & $3,00050 (2”)f/52508.3 & 12.5
Unistellar Odyssey Base & Pro8.8 lb.$2,300 & $4,00085 (3.3″)f/3.763203.4 & 4.1Auto focusing. Pro has eyepiece
Unistellar eQuinox 2 & eVscope 215.5 lb.$2,500 & $4,900114 (4.5”)f/3.954506.2 & 7.7Manual focusing & collimation. eVscope has eyepiece.
Celestron Origin Mark II~ 40 lb.$4,300152 (6”)f/2.23356.4
Information above initially as of August 2024 and updated periodically. Please refer to the manufacture or supplier for the latest specs and prices.

References and Reviews (Smart Telescopes)

Please note that FAS does not recommend or endorse any specific smart telescopes, we only provide information that is generally available.

Imaging Telescopes for Astrophotography

One of the most important piece of equipment for astrophotography is the telescope. This section could be extremely long, so we’ll only focus on a few possibilities. Your choice might be based on your ultimate imaging targets (Deep-Sky objects vs. Planets). Deep-Sky objects are best imaged with a short to medium focal length and a wide field of view. Planets generally require a longer focal length, which provides a narrower field of view. There is a useful website, which will help you determine the field of view for any setup.

There are a few useful accessories that could be added to your setup.

  • A Bahtinov Focus mask, if you manually focus your telescope.
  • An auto focuser, such as those from ZWO is also useful. The two are similar, however, the EAF Pro has an internal battery and bluetooth connectivity.
  • Optical elements such as a reducer or flattener.

Please note that FAS does not specifically recommend or endorse these or any other telescopes, we only provide information that is generally available.

Imaging Cameras for Astrophotography

The second most important piece of equipment for astrophotography is the camera. This section could be extremely long, so we’ll only focus on a few possibilities from ZWO, which can be used with the ZWO ASiair – more to come later. Also, see the smart cameras from ZWO. See below for information about Camera Sensors.

  • ASI533 Pro Series [1”, IMX533, 3008 x 3008 = 9.1 MP]. ZWO.
  • ASI183 Pro Series [1”, IMX183, 5496 x 3672 = 20.2 MP]. ZWO.
  • ASI585MC/MM Pro [1”x1.2”, IMX585, 3840 x 2160 = 8.3 MP]. ZWO. High Point Scientific. Agena Astro.
  • ASI294 Pro Series [2”x3″, IMX492, 8288 x 5644 = 46.8 MP]. ZWO.
  • ASI2600 Pro Series [APS-C, IMX571, 6248 x 4176 = 26.1 MP]. ZWO. High Point Scientific. Agena Astro. Amazon (Agena Astro).
  • ASI2600MC/MM DUO. ZWO.
  • ASI2400MC Pro [Full Frame, IMX410, 6072 x 4042 = 24.5 MP. ZWO.
  • ASI6200 Pro Series [Full Frame, IMX455, 9576 x 6388 = 61.2 MP]. ZWO.

Please note that FAS does not specifically recommend or endorse these or any other cameras, we only provide information that is generally available.

ZWO Harmonic Mounts for Astrophotography

The third most important piece of equipment for astrophotography is the mount. This section could be extremely long, so we’ll only focus on the two harmonic mounts provided by ZWO (AM3N, AM5N, and AM7).

  • The AM3N supports loads up to 8 kg and to 15 kg with a counterweight.
  • The AM5N supports loads up to 13-15 kg and to 20 kg with a counterweight.
  • The AM7 supports loads up to 20 kg and to 30 kg with a counterweight.

Pay close attention to how you power these mounts. The power ports are DC 5.5mm x 2.1mm barrel ports (DC 5521). The AM3N and AM5N have a DC port (for power) on its base. They also have a DC port (for power) and a USB-C port (for control) on the saddle. These can be used to connect to your ASiair without the cables getting in the way while the telescope moves. You might have to purchase a power cord – one does not come with harmonic mount. There are possibly four options for cables (depending on your power station). Make sure to check the specifications for these cables to make sure they work for your setup.

  • DC direct with barrel plugs on both ends.
  • USB C to DC barrel plug.
  • AC to DC adapter to DC barrel plug.
  • DC “car adaptor” to DC barrel plug.

If your power station is not delivering sufficient voltage, the harmonic mount will beep. One of our members can confirm this. His mount beeped for around a hour one night as he was trying to figure out the cause. Also, if the mount beeps while slewing, you might not be getting enough power.

Please note that FAS does not specifically recommend or endorse this or any other mount, we only provide information that is generally available.

Guide Telescopes & Cameras for Astrophotography

The Earth moves – yes it revolves and, as we all know, the objects we are imaging move away from our camera unless our setup tracks them. Therefore, another important area is the guide telescope & camera (unless you are using a camera such as the ZWO 2600MC duo or one of the smart cameras from ZWO).

  • “Mini Cameras.” ZWO.
  • “ASI220MM Mini(mono).” ZWO.

Please note that FAS does not specifically recommend or endorse these or any other guide telescopes and cameras, we only provide information that is generally available.

ZWO ASiair

One option for astrophotography that is getting a lot of attention is the ASiair from ZWO. There are currently two models (ASiair Mini and ASiair Plus). The ASiair Pro is an older model. Several FAS members are now using the ASiair. Also, an ASiair was recently added to the club’s observatory. A few images from the observatory are below.

Image Credits: Joe Haberthier and other FAS members.

Please note that FAS does not specifically recommend or endorse any specific equipment or setup, we only provide information that is generally available.

Notes on Using your ASiair
ASIAIR Main Screen and Options
  • The Main screen shows a series of icons across the top. Each will take you to the another page with more details as noted below.
    • ASIAIR Settings, including Wi-Fi and other information.
    • Main Camera Settings.
    • Guide Camera Settings.
    • Telescope Settings.
    • EFW: Filter Wheel Settings.
    • EAF: Electronic Auto Focuser.
    • Storage Settings (Files, including storage media). Click and choose your USB drive.
      • eMMC – files are being saved to the ASiair.
      • USB drive icon – files are being save to your USB drive.
  • The Main screen right hand side has icons for the main functions.
    • Preview. Go here to take a preview image and to manually move your mount.
    • PA (Polar Axis Calibration). Do this to orient your setup to the polar axis.
    • Live. Go here to take calibration and live images. Use the “burger” button for settings.
    • The Main screen left hand side has icons for various tools (Histogram, Focuser, Guiding, Crosshair, Annotate Image, …).
  • The Main screen lower left has a button with the Big Dipper. Click here to select an object to view.
Taking Images with Your ASIair
  • Choose an Object
    • Click on the “Big Dipper” icon to choose an object to image.
    • Choose an object to image. Use your finger to adjust the view, if necessary.
    • Wait for ASiair to plate solve and find your object.
    • Return to the previous screen.
  • Preview the image
    • Choose Preview from the drop down.
    • Click [EXP] to choose an exposure time (say 3 sec).
    • Click on Preview.
    • Return to the previous screen.
  • Select a Guide Star
    • Click on the graph in the top left to set a guide star.
    • Click refresh to reset the image.
    • (Optional) Choose a star (or skip this step and let the ASiair choose one automatically).
    • Click on the crosshair button.
    • ASiair will use your star or find a suitable guide star.
    • ASiair will start guiding.
    • Wait for the blue (RA) and red (DEC) lines to converge around the center line and for the graph at the bottom to track and show numbers.
    • If the red and blue lines diverge, go back, click refresh and repeat the process to select another star.
    • Return to the previous screen.
  • Start Taking Images
    • Choose Live from the drop down.
    • Click on Live.
    • Click on the menu (three vertical dots and lines) to choose your settings (Light, EXP, Save Every Frame).
    • Click on the big white button to start taking images.
  • Stop Taking Images
    • Click on the big white button to stop taking images.
    • Click on the SAVE button to save the final stacked image.
  • Stop Guiding
    • Click on the graph in the top left.
    • Click the stop button to stop guiding.
    • Return to the previous screen.
Calibrating and Using your Guide Camera with the ASiair

Click the refresh button to clear the image and start over. Then choose a star to track (optional). Click on the crosshair button and the ASiair will choose a star if you haven’t and start tracking. To stop guiding, click on the STOP button.

Initially, you must calibrate your guiding camera. The ASiair will do this automatically for your first object of the night. Note that you should point to an object low in the sky for this. If the declination is too high, the guide camera will have difficulties tracking and you will see an warning message. You should also perform a calibration when doing a meridian flip. In this case, click on the crosshair within the graph button and choose flip. You can also clear out the previous calibration, in which case a new calibration will take place for the next guide star.

While guiding, you want the red (DEC) and blue (RA) lines on the graph to be as close as possible to the center line without being consistently above or below. You also don’t want wide swings in either and you don’t want the lines to drift too far up or down. The ASiair takes an image to determine your guide camera’s position. It then determines the error in the position (in declination DEC and right ascension RA), and sends an adjustment to your mount. The RA Aggr and DEC Aggr will control the signal sent to your mount – for example, a 50% setting will send an adjustment equal to 50% of the calculated error.

  • If the adjustment is too small, the mount will not move enough and you will end up constantly above or below the center line. You might increase the percentage.
  • If the adjustment is too large, you can end up zigzagging back and forth. You might reduce the percentage.

You can also adjust the exposure time (EXP), the guiding camera’s gain, and the mount’s guiding speed. We’ve read that the exposure time should be between 1 and 4 seconds. An M setting for the guiding camera’s gain and .25x for the mount guiding speed might be a good starting point (to be determined). Be careful with these settings – take a picture of the initial settings before making changes, so you can reset everything back to the starting point.

ZWO Smart Cameras

Recently ZWO combined the ASiair with their imaging cameras for a combined 3 in 1 guiding, imaging, and control “smart camera” alternative. There are two models (ASI585MC Air and ASI2600MC Air). Note that these cameras work best within the ZWO software ecosystem – particularly with the ZWO auto-focuser and ASiair app. Although, they do support telescopes and mounts from other suppliers.

Please note that FAS does not specifically recommend or endorse any specific equipment or setup, we only provide information that is generally available.

Optical Elements

As you look at various options for Astrophotography, you will come across different optical elements that can be added to your setup. Typically these elements are one of the following.

  • Flattener – corrects for the curvature in a refractor’s lens and smooths out the stars in the corners of your image. Several are available including those from High Point Scientific, Agena Astro, and Astronomics.
  • Reducer – reduces the focal length to increase the field of view and capture more light. Several are available including those from ZWO, Agena Astro, and Astronomics.
  • Extender – extends the focal length to reduce the field of view and increase the magnification.

Please note that FAS does not specifically recommend or endorse these or any other specific elements, we only provide information that is generally available.

Filters for Astrophotography

Filters can be used to enhance your images. Prices listed below are for the 2” filters and are approximate. There are three general types.

UV/IR Cut Filters

UV/IR Cut Filters (aka Luminance Filters) cut out nonvisible (UV and IR) light and allow only visible light through. These are used for all deep-sky objects, but particularly for non-emission nebulae.

  • ZWO UV IR Cut Filter
  • Optolong UV/IR Cut Filter

Broadband Filters

Broadband Filters cut out the effects of light pollution. These can be used for most deep-sky objects. They reduce the impact of light pollution without narrowing the bandwidth of light. The Optolong L-Quad Enhanced might be a slight upgrade from their L-Pro.

  • Svbony SV260
  • Optolong L-Pro
  • Optolong L-Quad Enhanced

Dual Narrowband Filters

Dual Narrowband Filters (aka Duo Narrowband Filters) captured wavelengths from emission (and planetary) nebulae. ZWO includes one in its Seestar. These filters block out all but the Hα (656nm) and OIII (500nm) wavelengths, along with possibly a third wavelength. The narrower the bandwidth of the emitted light (e.g., 3nm vs. 10nm), the more unwanted light is blocked, however, the more exposure time is required because less overall Hα and OIII light is captured.

  • ZWO Duo-Band: 15nm bandwidth Hα and 35nm bandwidth OIII.
  • Svbony SV220 7nm bandwidth Hα and OIII.
  • Svbony SV220 3nm bandwidth Hα and OIII.
  • Optolong L-eNhance: 10nm bandwidth Hα, Hbeta, and 24nm bandwidth OIII.
  • Optolong L-Para: 10nm bandwidth Hα and OIII.
  • Optolong L-eXtreme: 7nm bandwidth Hα, and OIII.
  • Optolong L-Ultimate: 3nm bandwidth Hα and OIII.

ZWO Filters

Svbony Filters

Svbony offers a less expensive alternative to a few of the Optolong filters, although we have not determine the quality of these filters vs. those provided by Optolong.

  • Svbony SV260 broadband filter. [PURCHASE FROM: Svbony. Amazon.]
  • Svbony SV220 7nm dual-band filter. [PURCHASE FROM: Svbony. Amazon.]
  • Svbony SV200 3nm dual-band filter. [PURCHASE FROM: Svbony. Amazon.]

Optolong Filters

Optolong offers a series of filters, some of which several FAS members use. [PURCHASE FROM: Optolong. High Point Scientific. Agena Astro. Astronomics.]

Filters Trays & Wheels

To utilize filters, you will need a filter drawer such as one from ZWO. ZWO. High Point Scientific. Agena Astro. Note that there are both M42 and M54 sized filter drawers. Pay attention on how to install the filter drawer to obtain the correct 55mm back focus (ZWO). Another option is a filter wheel, which allows multiple filter to be installed and allows you to easily switch between them.

Please note that FAS does not specifically recommend or endorse these or any other filters, we only provide information that is generally available.

ZWO Electronic Automatic Focusers (EAF)

Focusing your telescope can be enhanced by using the ZWO Electronic Automatic Focusers (EAF). There are two models.

The electronic focuser will find a star and adjust the focus while plotting the width of the star vs. the focus position. It will first create a V curve that looks more like a U, but shows where the optimal focus position is (position which gives the smallest star diameter). It will then choose a few additional points off the optimal and take smaller increments to confirm the optimal focus position.

Please note that FAS does not specifically recommend or endorse this or any other focuser, we only provide information that is generally available.

Pier Extentions

More on this coming soon …

Please note that FAS does not specifically recommend or endorse these or any other pier extenders, we only provide information that is generally available.

Power Stations

Once you have all your equipment purchased and setup, you need POWER! Yes your astrophotography equipment needs some electricity for it all to operate properly.

If you have a ZWO centric setup, the power flows from the battery to the harmonic mount and then to the ASiar, which, in turn, powers the rest of the equipment. However, one can also run the power from the battery to the ASiair and then to the harmonic mount. This flow utilizes 12 volt/3 amp DC current running through two cables with 5.5mm x 2.1mm DC barrel (DC 5521) plugs and the corresponding ports on the harmonic mount and ASiair. The ASiair has several USB ports for the rest of your equipment. To get through an entire night of observing, a battery with a minimum capacity of around 250 Wh is required. However, you might do better with 500 Wh or 700 Wh.

  • A battery with the appropriate DC barrel ports appears to be the best option (at least for the ZWO mounts).
  • A battery’s AC port along with an AC to DC barrel plug cable might work.
  • A battery’s DC “car port” along with a DC barrel plug cable might also work, however, it might not provide enough power for the mount, camera, and a dew heater.
  • A battery’s USB-C port along with a DC barrel plug cable has not been verified to work, however, it might be a possibility.

After taking a short survey of a few FAS members and doing some research, we’ve identified a number of power stations that might be appropriate. Several, in particular, look promising (==>). However, DO YOUR OWN RESEARCH before purchasing any of these or other batteries and cords. They have NOT ALL BEEN FULLY TESTED with a ZWO setup or any other astrophotography equipment. Always consult with your astrophotography equipment supplier as to which power station and power cords are best for their equipment. Stay tuned, we’ll update this section as we get more information and suggestions.

  • “Power, Batteries, Hubs & Cables.” High Point Scientific.
  • Apertura / High Point Scientific.
    • “Apertura Portable Telescope Power Supply” 155Wh – with barrel ports. High Point Scientific.
    • ==> “Apertura All Night Imaging Power Supply – 518Wh Lithium.” 518 Wh – with barrel ports. High Point Scientific.
  • Jackery
    • “Explorer 300 Portable Power Station.” 293 Wh – without barrel ports. Jackery.  
    • ==> “Explorer 500 Portable Power Station.” 500 Wh – with barrel ports. Jackery. Amazon.
    • “Explorer 1000 Portable Power Station.” 1070 Wh – without barrel ports. Jackery. Amazon.
  • EcoFlow
    • “River.” 256 Wh – with barrel ports. Discontinued.
    • “River 2.” 240 Wh – without barrel ports. EcoFlow. Amazon.
    • “River 3.” 245 Wh – without barrel ports. EcoFlow. Amazon.
    • “River 3 Plus.” 286 Wh – without barrel ports. EcoFlow. Amazon.
    • ==> “River 2 Max.” 512 Wh – with barrel ports. EcoFlow. Amazon.
    • ==> “River 2 Pro.” 716 Wh – with barrel ports. EcoFlow. Amazon.
  • Bluetti
    • “EB3A.” 268 Wh – with barrel ports. Bluetti.
    • “Elite 30 V2.” 288 Wh – with barrel ports. Bluetti.
    • “Pioneer 50 (AC60).” 403 Wh – with barrel ports. Bluetti.
    • ==> “EB70S.” 716Wh – with barrel ports. Amazon.
    • “Elite 100 V2.” 1024 Wh – with barrel ports? Amazon.
  • Goal Zero
    • “Yeti 300.” 297 Wh – without barrel ports. Goal Zero.
    • “Yeti 500.” 499 Wh – without barrel ports. Goal Zero.
    • “Yeti 700.” 677 Wh – without barrel ports. Goal Zero.
  • Anker
    • “SOLIX C300 DC Power Bank Station.” 288 Wh – without barrel ports. Amazon.
    • “SOLIX C800 Plus Portable Power Station.” 768 Wh – without barrel ports. Amazon.
  • Others
    • ==> “OUPES Exodus 1200 Portable Power Station.” Amazon.

Please note that FAS does not specifically recommend or endorse these or any other power stations or batteries, we only provide information that is generally available.

APPENDIX – Now for some Math!

It seems that it isn’t easy to figure out how “big” of a power station you need. Most have power capacities stated in Watt Hours (Wh). Your electronics require a certain power level (watts per hour). Here are some notes that might make this easier to understand.

  • If you need, say 30 watts per hour, and your power station has a capacity of 300 watts, you can expect it to last around 10 hours. There are other factors that influence this including temperature. A typically lithium battery’s capacity is reduced as the temperature drops.
  • Sometimes a power pack has capacity stated in terms of milliamps hours (mAh). Not to worry, most power packs utilize 12 volt current, therefore, to find the wattage, just multiple the mAh by .012 (the voltage divided 1,000). For example a 10,000 mAh power pack has the capacity of 120 Wh.
  • What gets tricky is the amps (not the mAh). Most DC power sources are 12 volts. However, the amps vary from, typically, 3 amps to 5 amps to 10 amps. The good news, is you can determine the power (watts) by multiplying the voltage (12) by the amps. 12 x 3 = 36 watts, 12 x 5 = 60 watts, and 12 x 10 = 120 watts.
  • If your electronics require, say 12 volts with 3 amps = 36 watts, you need to make sure your power station provides this much power (or more? – we’re working on this question – more to come).
  • A 12 volt battery actually measures around 12.6 volts, but the average discharge is 12 volts. We’re working on this one as well – more to come.
  • As your battery discharges, the voltage it provides decreases until it is fully discharged and the delivered voltage is around 10.5.
  • At the root of all this is Ohm’s Law, which states that:
    • Current (I / Amps) = Voltage (V / Volts) divided by Resistance (R / Ohms).
    • Power (W / Watts) = Current (I / Amps) times Voltage (V / Volts).

Dew Heaters

After Clouds and light pollution, the biggest problem astrophotographers run into is dew. The good news is that you can combat dew a couple different ways. First has a dew shield (that also acts as a light pollution shield). Second, add a dew heater to your setup. This keeps the telescope lens above the dew point and prevents dew from forming. It can also keep frost from forming on the lens during the winter.

There are several “wrap around strap” dew heaters available. Also, some systems, such as the Seestars, have dew heaters built in.

Please note that FAS does not specifically recommend or endorse these or any other dew heaters, we only provide information that is generally available.

Counterweight

Both the ZWO (AM3N and AM5N) mounts work well without a counter-weight. However, if your load is greater than 8 kg (AM3N) or 13-15 kg (AM5N), ZWO recommends that you use a counterweight.

Please note that FAS does not specifically recommend or endorse this or any other accessory, we only provide information that is generally available.

Back Focus

Back focus means, roughly, that there needs to be a specific distance between the lens of the last optical element (e.g., a flattener, or a reducer) and the camera sensor. More specifically, back focus is measured from the edge (flange) of the optical device and the camera sensor. In many cases, the back focus required is 55 mm. Again, this means your camera must be 55 mm back from the optical element to achieve a proper focus.

If you are using a DSLR camera, a t-ring can be added to achieve the proper back focus. For ZWO’s 2600 cameras, they come with two adapters (one 16.5 mm and the other 21 mm). The camera itself adds 17.5 mm, and you have a total of 55 mm.

Bahtinov Mask

If you are manually focusing your telescope, you probably want to use a Bahtinov Mask. Place the mask on the end of the telescope. Point toward a bright star. Adjust the focus so that the middle line is between the other two lines.

Thread Size

Just to complicate things, various equipment (particularly telescopes and cameras) can have different thread sizes. As an example, the Askar V telescope flatteners, extenders, and reducers have 48mm threads, while the ZWO ASI2600 camera has 54mm threads. This requires a M54M to M48F adapter (which comes with this camera).

When using a small adapter, it can get “stuck”. The folks from High Point Scientific offer a suggestion on how to get it “unstuck.”

If you look closely at the edge of the adapter, you’ll see two small indentations. These are designed for a spanner wrench, though you can also use the tips of a small tool to gently work the ring out. Be very mindful not to slip the tool and scratch the lens. If it’s really stubborn, one last-resort trick is to apply a tiny amount of non-permanent thread locker to the male threads of a matching part, seat it into the flattener, and once it cures, carefully back it out with the stuck ring attached. If you try this method, make sure to keep everything upright so nothing can drip onto the lens element.

Please note that FAS does not specifically recommend or endorse these or any other spanner wrenches, we only provide information that is generally available.

Dithering

Dithering is a process where the frame of your telescope (or camera) is moved slightly to adjust the area of the sky being captured. This shifts the stars to a slightly different place to avoid the over sampling of ”Hot Pixels” and noise. It can be thought of as randomizing errors so they don’t build on each other. A few FAS members suggest dithering every 3 images.

Camera Sensors

Most cameras today have a complementary metal-oxide semiconductor (CMOS) as a chip, compared with a charged-coupled device (CCD) sensors of a few years ago due to the lower power consumption of the CMOS chip. Cameras also offer different image frames ranging from 1” in diameter to APS-C to Full Frame 35mm based on the chip used. There is a useful website, which will help you determine the field of view for any setup.

Image Credit: Autopilot, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons

Please note that FAS does not specifically recommend or endorse these or any other cameras, we only provide information that is generally available.

Camera Gain and Offset

More to come …

Signal to Noise Ratio

The signal to noise ratio (SNR) is a measure of the quality of your image. It is the “good” light capture for your image divided by the “bad” light, which is the noise from various sources including light pollution, your camera, and sky glow (e.g., the Moon).

  • Longer exposures improve the signal to noise ratio. However, too long and you might experience tracking issues (i.e., star trails) and the risk of artifacts such as satellite trails.
  • Longer integration time (i.e., stacking more subs) also improves the signal to noise ratio. However, there might be a diminishing return as more subs are added.
  • Light pollution and sky glow adds to the noise level. Filters can help with this.

SNR = Signal / Noise. In some cases, the signal is added to the noise, so that a perfect SNR = 1. Longer exposure time and longer integration time improves our images because noise increases at a slower rate than the signal. However, there is a diminishing return because the SNR will increase at a non-linear (possibly square root) rate. A doubling of the number of subs results in an 1.41 increase in the SNR. More to come here as we understand this more …

One might think that there is an equivalent SNR between exposure times and integration time. For example, 1 sub with 100 second exposure time should have the same SNR as 10 subs with 10 second exposure time. Videos from Deep Sky Detail discusses some of this. In particular, there is a difference due to “read noise” that is added for each subframe. However, light pollution typically is the greatest source of noise and this washes out the difference due to the read noise.

Image Exposure & Integration Time

This section is a work in progress and will be updated. More to come …

One question that comes up a lot is, how long should my individual sub exposure times be and how long should the integration time (stacking subs) be to get a good final image? The answers is, it depends. In any event, one is always trying to improve the signal to noise ratio (see above).

  • Always shoot multiple exposures and stack the results – in other words, long integration time. Typically, the more the better, however, there might be a diminishing return as you add more subs.
  • The longer the subs exposure, the more light you will capture for each sub and the better the signal to noise ratio, However, if your exposure time is too long, you will start to see artifacts such as star trails. The better the alignment and tracking, the longer each exposure can be. Therfore, using a guide telescope and camera definitely helps.

For a Seestar in alt/az mode, 10 seconds seems to be the best and around 1/2 hour of images works well. Less and the final image isn’t too bright. More and you start to get field rotation artifacts in the corners. If you re-stack your images, the field rotation isn’t as noticeable and longer . For a Seestar in EQ mode, 20 seconds seems to be the sweet spot. Some use 30 seconds. The 60 second option gets a lot of star trails unless you have a perfect alignment. Field rotation is not an issue, so take as many subs as practical.

For Standard Astrophotography setups, the exposure time and integration time depends on many factors, particularly the f/ ratio, level of light pollution, and accuracy of tracking. Deep Sky Detail has several videos that discuss this – maybe in too much detail. The article Astrophotography – Long or Short Exposures recommends 3 to 5 minute exposures with 50 to 100 subs.

Peter Zelinka, in a YouTube video, covers this in a simple way. You need to double your integration time to achieve an noticeable improvement. In other words, 1 hour to 2 hours to 4 hours to 8 hours to 16 hours to 32 hours to 64 hours to 128 hours. You also get the same improvement by reducing the focal ratio (f/8 to f/5.6 to f/4 to f/2.8 to f/2).

Some point to the “500 rule”, where the maximum exposure time is equal to 500 divided by the focal length times a crop factor. The crop factor has to do with the sensor and is 1 for full frame and around 1.5 for APS-C. However, this formula doesn’t make much sense when you are auto tracking using a polar alignment and guide scope.

Sharing Astrophotography Images

There are several websites that support the hosting and sharing of your astrophotos. For photos by FAS members, see FAS Member Astrophotography.

Please note that FAS does not specifically recommend or endorse this or any other website, we only provide information that is generally available.

Remote Astrophotography

For the more advanced photographer or for someone who wants to try astrophotography before investing in any equipment, there are options to do astrophotography remotely. Typically these options are not free, but require a subscription or some type of cost per use. There are three different types of setups.

  • BUY: The observatory provides the images, which subscribers can access.
  • RENT: The observatory provides the equipment, which can be rented remotely.
  • OWN: An individual sends their equipment to the remote site to be operated by the observatory.

Please note that FAS does not offically recommend or endorse any specific remote telescope offering, we only provide information that is generally available.

MicroObservatory (Center for Astrophysics | Harvard & Smithsonian)

This is a free option to capture some images of the night sky. Here are instructions to capture and process an image (See the videos below for more information). We are still reviewing this and have not tested it out.

We have not tested or evaluate all of these options.

Installing Astrophotography Plug-Ins on a Mac

Unfortunately, The sources of several Astrophotography tools are not registered in a way a Mac recognizes them as legitimate software. We have had difficulties loading StarNet++ and the two Cosmic Clarity plug-ins. Here is some information that might help.

A possible generic approach is: Choose (Apple) System Settings > Privacy & Security > Scroll way down to Security > Click the Open Anyway button.
Then when you run the script, choose Open Anyway and enter your system password.

Go here for help in downloading StarNet++ to a Mac =>

Downloading StarNetDownload

Please note that FAS does not specifically recommend or endorse any process to override the security settings on your Mac.
Please do so at your own risk.

Image Processing (Tools & Techniques)

Capturing images is only part of the process for astrophotography. To produce really great images, they must be processed, stacked, and combined. Today, it seems that most people doing astrophotography use one of three packages: Siril (which is free), Astro Pixel Processor, or PixInsight – with PixInsight becoming more and more the popular choice. DeepSky Stacker is used by many to stack their frames. GraXpert and StarNet++ are used to enhance images in Siril and possibly other packages. Seti Astro Suite offers Cosmic Clarity for image sharpening. RC Astro has several plug-ins (e.g., BlurXTerminator and StarXTerminator) for PixInsight.

In this section

Calibration Frames

Enhancing your images often requires the use of calibration frames. Flats, biases, and dark frames are often taken each time you use your setup. They are “combined” with your images (light frames) during your shooting and then again during your stacking.

  • Flat Frames: Taken against a white background. These smooth out differences in light intensity due to dust and other impurities. If using an ASiair, set the exposure to Auto.
  • Bias Frames: Taken against a dark target. These are used to eliminate camera noise from your images. Set the exposure to the fastest as possible (e.g., 1/1000 seconds) and take many images (e.g. 50).
  • Dark Frames: Taken against a dark target at the same temperature as your imaging. These are used to eliminate thermal noise (temperature differences) from your images. Use the same exposure time as your light frames.
  • Light Frames: These are your images (fit files).

Stacking

Stacking allows you to take advantage of multiple images and combine them into one. Systems such as the ASiair and Seestar will auto stack as you go. Although, you probably want to save individual frames (fit files) for later stacking. This offers the advantage of rejecting frames that have distortions, star trails, or other deformities. The more subframes used, the better the signal to noise ratio. Package such as Siril and PixInsight provide scripts and processes for stacking image.

Plate Solving

In many cases your images need to be Plate Solved. This is a process to determine the correct coordinates (right ascension and declination) for your image. In essences, the stars in your image are compared with a catalog to determine these coordinates. It is required before doing a color calibration in Siril. It is also done after uploading images to Telescopius.

Background Gradient Removal

Images are usually taken in less than perfect conditions. Light pollution is all around us. On many nights the Moon interferes with our view of deep-sky objects. As a result, our images come out with uneven backgrounds and possibly a grayish background. There are several ways of addressing this. If possible, always utilize calibration frames. Also, many software tools, such as GraXpert and Auto Background Extraction (Seti Astro), will perform a background extraction to address the problem. Riccardo Paterniti has introduced VeraLux Nox.

Color Calibration

In many cases, the colors in your image are not perfectly correct. To address this, both Siril and PixInsight have ways of performing a color calibration. Spectrophotometric Color Calibration is the latest, and seemingly preferred method, for both. You must perform a plate solve first and make sure you have loaded the latest Gaia database.

Deconvolution / Star Sharpening

Deconvolution is a method of removing “blur” from your images and sharping your image, particularly the stars. There are several tools available that will do this: GraXpert, Cosmic Clarity, and BlurXTerminator.

Within Siril, there is a process, which is applied in two steps using the linear (non-stretched) image.

  • First, determine the point-spread function (PSF), which is a measure of the amount of blur. This is usually done by looking at a star, which should be a point source of light – but usually is not.
  • Second, the PSF value is used to “correct” the image. Typically, an algorithm is applied. the Richardson-Lucy deconvolution algorithm is the usual choice. It is applied through a series of iterations, which you specify. If done well, the stars will look better. If done poorly (typically too many iterations), you will see dark areas around the stars – this means you went too far.

Noise Reduction

One of the challenges with astrophotography is the manage the noise in your images. Typically, images are taken of very faint objects and longer exposures are required. The problem is that these exposures capture background noise in addition to the target. The idea is to maximize the “signal to noise ratio.” That is, maximize the light from the target, while, at the same time minimize the noise.

Two of the best techniques for this are dithering (discussed elsewhere) and image stacking (discussed elsewhere). However, there are other approaches and, in particular, software available to denoise images. Three of the most common are GraXpert, Cosmic Clarity, and NoiseXTerminator. Riccardo Paterniti has introduced a new VeraLux script for denoising in Siril. SyQon has introduced SyQon-Prism also for Siril.

Whatever the approach, the challenge is to enhance/brighten the target object without overly enhancing the noise. One article below suggests you apply noise reduction early in your workflow. This avoids compounding the noise in later steps.

Drizzle

Drizzle is a method used to increase the sharpness of your images. It is a processes initially created for the Hubble Telescope. The main idea is to take (under-sampled) images, reduce the pixel size, and fill in the image with more pixels.

Star Removal

When you process your image it is often useful to remove the stars, process/stretch your underlying image, and then recombine the result with the stars.

StarNet++ will handle this within Siril. Siril also has a VeraLux script to recombine the stars and Zenith a SyQon script to remove the stars.

PixInsight uses StarXTerminator from RC Astro to handling this. It might also have StarNet++.

Stretching Images

Most image processing software produces “final” jpeg images, which can be viewed by most applications. They also produce fit files, which can only be viewed using other astro-image packages. These Fit files are typically images in a 14 bit (or maybe 12 bit) format. For us to see anything, the information needs to be “stretched” into a 16 bit format. The simplest way to do this is by performing a stretch, which multiplies by 4 to stretch a 14 bit (0 to 16,383) image into a 16 bit (0 to 65,535) image.

However, you can do more than simply multiply by a number. Generally, when you are stretching an image, you start with a linear view. This is the way the camera records the information, but not the way our eyes see it. With the initial linear view, most of the useful information in the image is over on the left hand side. When you stretch the image, you are adjusting the pixels in a non-linear way so that much of the information is shifted to the mid tones, and as such, becomes more visible. Stretching also increases the contrast between the darker areas and the lighter areas in your image.

There are many stretching techniques – See below for much more information. Central to stretching is the histogram, which provide a graphical view of how the information has been stretched. The two simple approaches for stretching are to adjust levels and adjust curves. Three other techniques are available: ASINH transformation, Histogram transformation (HT), and General Histogram Stretch (GHS). Finally, there are three scripts that allow you to stretch in a more automatic way using parameters: Seti Astro Statistical Stretch, VeraLux HyperMetric Stretch, and Multiscale Adaptive Stretch (MAS).

The Histogram

Your image is composed of pixels, which have a value that defines the brightness of each. The allowable values depend on the bit size. Each pixel is assigned a number corresponding to its brightness (or three numbers, RGB, if in color). The larger the number, the brighter the pixel.

  • 8 bit images have values from 0 to 256
  • 14 bit images have values from 0 to 16,383
  • 16 bit images have values from 0 to 65,536

The histogram is displayed on a graph with two axes (horizontal and vertical).

  • The allowable brightness range of the pixels contained within your image is displayed across the horizontal axis from darkest to lightest. Its range depends on the bit size of the image.
  • The vertical axis (and the histogram) shows the number of pixels with each level of brightness.

Initially, with a linear view, there are many dark pixels – so the distribution is skewed to the left and the image is mostly dark. When you preform a stretch, the resulting histogram shows the distribution of brighter pixels (now more in the middle) and is shaped more like a standard bell curve.

  • The pixels for the sky are toward the left (darker) and the stars (brighter) to the right.
  • Your nebula or galaxy is represented by the midtones and the peak of the histogram somewhere in the middle.
  • The wider the histogram (the larger the standard deviation), the greater the contrast in your image – and the greater the noise in your images.
  • If your histogram has a flat area to the left, this means that none of the pixels have the darkest values. It could be because the sky is never completely black and there is some degree of light pollution. Typically, you can remove this area and shift the histogram all the way over to the left to darken the sky. Don’t go too far and clip some of the useful information.
  • If your histogram is too far to the left, your image will be dark and underexposed.
  • If your histogram is too far to the right, your image will be washed out and overexposed.

Adjust the Levels

Simple manual stretching involves adjusting the levels by dragging three markers (black point, gray/mid point, white point). You might do this several times. The end result is to eliminate areas to the left with no data and to bring the histogram more to the center.

  • Move the black point to the right to eliminate any area with no histogram values. Don’t go too far, otherwise you will clip off some useful data.
  • Move the gray point to the left to spread out the useful part of the image. This will brighten up the object you are focusing on.
  • Typically leave the white point slider alone.
Level Adjustment from Siril.
C. Richard et al., Journal of Open Source Software, 2024, 9(102), 7242. DOI: 10.21105/joss.07242.

Adjust the Curve

Curve stretching involves adjusting the histogram curve. You start with a line going from the lower left to the upper right. This represents the adjustments to the histogram curve at each point along the horizontal axis. You start with no adjustments (a line). Typically, you will drag the left part of the curve down to reduce the pixel values and increase the dark portion of your image. Then drag the mid and right parts up to increase the pixel values and the brightness of the lighter portions. The end result is usually an S shaped curve.

Curve Adjustment from Siril.
C. Richard et al., Journal of Open Source Software, 2024, 9(102), 7242. DOI: 10.21105/joss.07242.

Other Stretching Techniques

There are several other stretching techniques and formulas. Many packages come with an automatic stretch (e.g., Siril and PixInsight). This can be used to do a reasonable initial (or possibly final) stretch. These techniques used formulas to transform your image from a linear to a non-linear state. These notes have been adapted from Siril. PixInsight could have additional options.

ASIHN Transformation

This is often used as an initial stretch before adjusting levels or curves. In Siril, there are two settings (The Stretch Factor and Black Point). Increasing the black point will dampen the stretch factor to preserve the dark background.

Histogram Transformation (HT)

In Siril, you can perform an auto stretch and then manually adjust the levels (black point, gray point, and white point). In Siril, there is an automatic stretching option, which uses a Midtone Transfer Function Transformation (MTF).

Generalize Hyperbolic Stretch (GHS)

In Siril and PixInsight, this is a more robust approach with several settings that can be used with the Generalize Hyperbolic Transform.

  • Stretch Factor (ln(D+1)) is the primary setting use to adjust stretch factor D.
  • Symmetry Point (SP) is used to control the midpoint of the S curve. You might start with the Symmetry Point at .5 (right in the middle). You might also select an empty area and use that to set the symmetry point.
  • Local Stretch Intensity (b) is used to control the shape of the S curve. You might zoom into to a preview area and use the local stretch intensity to sharpen the stars.
  • Shadow (SP) and Highlight (HP) protection points limit how extreme the dark and bright adjustments will be.

There are a few other GHS options including Modified Arcsinh Transform, which is similar to the ASIHN transformation, and the Linear Stretch (BP Shift), which allows you to adjust the black point.

Seti Astro Statistical Stretch

Seti Astro has developed an automated statistical stretch routing. More to come here…

VeraLux HyperMetric Stretch

Riccardo Paterniti has developed an alternative to the more standard stretching methods called VeraLux Hypermetric stretching. It is available for both Siril and PixInsight. One of our members has been testing it out. So far, he likes to set the background to .15 (down from the default .20) and the color saturation over to the left (less saturated color, which seems to preserve more details). He also likes to follow up with some curve adjustments to brighten the image, which also increases the noise. However, you might find a different approach that works for you.

Multiscale Adaptive Stretch (MAS)

PixInsight has a new routine for stretching called Multiscale Adaptive Stretch (MAS). More to come here…

Processing Multi-Night Images

In many cases, you can just combine all your lights and calibration frames together for all nights and your results will not be too bad. However, your calibration frames might be different night to night. In this case, you really want to process each night’s lights together with the corresponding calibration frames for that night.

Sirilic might be the answer for this if you use Siril.

Rich from Deep Space Astro has a process you can use in Siril without Sirilic.

  1. Stack each night independently using the standard script OSC_Preprocssing.ssf.
  2. For each night, keep the pp_lights files found in the process folder.
  3. Rename the pp_light_# files to something like pp_lights_n_, where n is the night – otherwise you will have multiple sets of pp_light_#s with the same name.
  4. Copy all the pp_light_n_# files to a new Lights folder.
  5. Stack the comined pp_lights using the script OSC_Preprocessing_WithoutDBF.ssf.
  6. Continue with your standard workflow.

Naztronomy also has a script (Naztronomy-OSC_PP.py) for processing multi-night images in Siril.

Hubble Pallet

Emission Nebulae emit light in three distinct wavelengths, Halpha (696 nm), SII (672 nm), and OIII (496 nm). The Hubble Pallet was created by NASA (Hubble Telescope) as a way to map these three wavelengths into different colors: Halpha (Red), SII (Green), and OIII (Blue). The best way to create an image in the Hubble Pallet is to capture separate monochrome images at these three wavelengths using three different narrow band filters. Then map the resulting images into the Hubble colors (one for each set of images at the different wavelengths).

Photo (Image) Processing settings

Here is a summary of the many image (photo) processing settings available in most software. The articles below discuss some of the steps you might go through using these settings to enhance your images.

  • Exposure: Change the overall light the image captures, increasing or decreasing the brightness of all pixels.
    • Underexposed: Lack dark details.
    • Overexposed: Lack light details.
  • Brightness: Change how light or dark the image is, increasing the dimmer pixels.
  • Brilliance: A more complex (algorithmic?) method of increasing or reducing an image’s brightness.
  • Contrast: The difference between the brightest and darkest parts of your image.
  • Black Point: The darkest part of your image.
  • Noise Reduction: Removes the graininess in your image.
  • Sharpness: The difference between an object and its background.
  • Vignette: Reduces the sharpness at the image’s edges.
  • Color Adjustments.
    • Color Saturation: The intensity of the image colors.
    • Temperature: Adjustment of blues and reds.
      • Warm: More of reddish tone.
      • Cool: More of a bluish tone.
    • Tint: Adjustment of greens and magenta.

Simple Adjustments

After stacking your images (with calibration frames), here are a few very simple adjustments that you might try to further improve your image. However, a more formal workflow using some of the standard astrophotography software (such as Siril and PixInsight) will give you better results.

Examples of these simple adjustments are below. This is very much a work in process and actual image settings may vary from those noted.

  • Increase the Brightness [How light or dark the image is] particularly if the image is dim.
  • Increase the Contrast [Difference between the darkest and lightest parts] to +30 (or less if the color is too dark).
  • Increase the Black Point [Darkest part of the image] to +30 (or more if there are still residual light areas).
  • Increase the Color Saturation [Color Intensity] to +10 (maybe).

Generic Workflow

One of the challenges of working with astrophotography is developing a workflow you can consistently follow rather than pushing a bunch of buttons until your image looks good. Workflows differ depending on the software used. However, here is a general overview you can follow. Individual steps might be performed in a different order.

  1. Take and save your individual Light frames. Use long exposures – the longer the better.
  2. Take your calibration frames (darks, biases, and flats).
  3. Review your individual Light frames and remove those that have distortions (clouds, trees, and streaks)
  4. Stack your images. Include your calibration frames.
  5. Crop out the “pixellation” and other distortions around the edges.
  6. Extract the Background to remove the gradients.
  7. Perform a “Color Calibration” to correct the color of the stars and object.
  8. Remove the stars from the underlying object and background.
  9. Stretch your starless image. Maybe do an initial stretch and then fine tune it.
  10. Stretch your star-mask image.
  11. Recombine the stars with the underlying object and background.
  12. Fine tune your image. These steps could be done earlier.
    • Remove the excess Green noise (maybe).
    • Perform deconvolution to sharpen your stars. Possibly do this before removing the stars.
    • Remove noise from your image. Possibly do this while stretching the starless image.
    • Adjust the color saturation to enhance the colors.

AI (and Image Editing) in Astrophotography

As with everything else nowadays, AI is creeping into astrophotography, particularly with image processing. The question is: Is AI a legitimate way to process images or are we cheating? Another question might be, how much editing and enhancements are allowed for your astrophotography images. More to come here …

Image Processing Software

There is a multitude of image processing software available. We can’t cover them all, but can provide an outline of which ones appear to be the more commonly used. ZWO’s ASIStudio is designed to be used with the output of ZWO’s ASiair. DeepSky Stacker, GraXpert, Cosmic Clarity, and StarNet perform very specific functions (stacking, background extraction, and star extraction respectively). Siril, Astro Pixel Processor, and PixInsight are three fully functional astro-processing packages. RC Astro has several plug-ins for PixInsight. Gimp is a free alternative to Photo Shop. N.I.N.A. is a popular PC based software.

In this section

ZWO ASIStudio

If you are processing images from an ASiair, you might use ASIStudio from ZWO to stack and stretch your images.

ASIDeepStack is used to stack and stretch images. After some experimentation, processing images with calibration frames yields some good results.

ASIFitsView is used to view fits frames.

Go here for an ASIDeepSack workflow =>

ASIDeepStack Work FlowDownload

Please note that FAS does not specifically recommend or endorse this or any other software, we only provide information that is generally available.

DeepSky Stacker (DSS)

DeepSky Stacker is an alternative software package you might consider to stack your images. It can also be used to review your FIT frames and discard ones with issues. It appears that DSS only runs on in a Windows environment and not on a Mac. (More to come here.)

Please note that FAS does not specifically recommend or endorse this or any other software, we only provide information that is generally available.

GraXpert

GraXpert is a software package designed to help you remove gradients from your images. You can run it from a script from either Siril or PixInsight. If you run it as a stand alone, it has five basic functions/steps.

  1. Loading: Load your image. This could be a stacked fit file from ASIStudio or Siril.
  2. Crop: Crop your image to remove noise and other defects around the edges.
  3. Background Extraction: Extract the background to remove gradients.
    • Method: RBF (same as Siril) or AI (enhanced & automatic)
    • (RBF Only) Points per Line: Adjust this to decrease or increase the number of background squares.
    • (RBF Only) Grid Tolerance: reduce or increase the background coverage. Increase this if light areas are not included in the background. Decrease this if too much of the target object is included in the background.
    • Smoothing: reduce this to remove more gradients. Increase it to remove less gradients.
  4. Denoising: Remove the noise from your image.
    • Denoising Strength: Reduce or Increase this as needed.
  5. Saving: Save the resulting file either as a processed fit (non-stretched) or as a stretched fit file.

As you work with your image, stretch it so you can follow the process. There are a three options to choose from.

  • 10% to 30% Bg, 2 or 3 sigma, which allows you to choose a less to more aggressive stretching. The more aggressive (30% Bg) allows you to clearly see the gradients in the background. Once you remove the background, switch back to a lower percentage for a more reasonable image.
  • Channels linked … (more to come here).
  • The Saturation allows you to reduce or increate the color saturation.

You can view the results of each step by clicking on the options at the top.

  • Original
  • Gradient-Corrected
  • Background
  • Denoised

Please note that FAS does not specifically recommend or endorse this or any other software, we only provide information that is generally available.

StarNet++

StarNet is a software package that allows you to split your image into stars and the target nebula. It is integrated with PixInsight and with Siril. You might have trouble loading it on a Mac. See here for some possible help.

Please note that FAS does not specifically recommend or endorse this or any other software, we only provide information that is generally available.

Astrosharp

Astrosharp is a free software package that will sharpen your astro-images. It runs only on Windows – sorry nothing for Macs at the moment.

Please note that FAS does not specifically recommend or endorse this or any other software, we only provide information that is generally available.

Cosmic Clarity

Seti Astro offers Cosmic Clarity with several routines that you can use to process your astro-images. Cosmic Clarity integrates with both Siril (through python scripts) and PixInsight. You might have trouble loading and running Cosmic Clarity routines on a Mac. See here for some possible help.

  • Cosmic Clarity sharpening will run a deconvolution routing to sharpen your image. It can be run for stellar only, non-stellar only, or both.
  • Cosmic Clarity denoise will remove noise from your image. It can be applied for Luminance (bright and dark), Full (RGB channels), or Separate.
  • Cosmic Clarity satellite will remove satellite trails from your sub-images. The Siril script appears to work with only a single image.
  • Cosmic Clarity darkstar wil remove the stars from your image.
  • Cosmic Clarity superres will improve the resolution of your images.

Please note that FAS does not specifically recommend or endorse this or any other software, we only provide information that is generally available.

VeraLux Scripts (for Siril)

There are several VeraLux scripts from Riccardo Paterniti available in Siril. Rich from Deep Space Astro has videos that describe each of these.

SyQon Scripts (for Siril)

SyQon offers two scripts: SyQon-Starless (remove stars) and SyQon-Prism (denoising). More to come here …

    Please note that FAS does not specifically recommend or endorse this or any other software, we only provide information that is generally available.

    Seti Astro Suite (SAS)

    Seti Astro also offers its Seti Astro Suite (SAS). More to come here …

    Please note that FAS does not specifically recommend or endorse this or any other software, we only provide information that is generally available.

    Siril

    As you get more comfortable with processing your images, you might take a look at Siril, which is a free open sources astro image processing package. A short overview is found below along with many references. In particular, Deep Space Astro has many good videos on how to use Siril.

    C. Richard et al., Journal of Open Source Software, 2024, 9(102), 7242. DOI: 10.21105/joss.07242

    Siril Workflow / How to use Siril

    In general, a workflow for Siril involves several steps. Below is a workflow used by one of our members (Adapted from several online posts and videos including those from Deep Space Astro). You may find other ways to utilize Siril and its functionality. In any case, there are a few steps that are useful.

    Your general workflow might be this: stack, crop, extract background, plate solve & color calibration, star sharpen, star removal, stretch (and denoise) the starless image, stretch and recombine the star master.

    1. Make sure to Save your subs to the appropriate folders (Lights, Flats, Darks, Biases).
    2. Point Siril’s Home page to the folder containing your subs.
    3. Stack your images with a script – typically OSC_Preprocessing.ssf (if you have calibration frames), OSC_Preprocessing_WithoutDBF.ssf (without calibration frames), or Seestar_Preprocessing.ssf (for Seestar images). See Processing Multi-Night images for suggestions on how to stack images taken over several nights.
    4. Before stretching your image, it will appear dark in Linear format. You can AutoStretch it to see what it would look like after stretching.
    5. Fine-tune your stacked image by cropping the image, removing background gradients, sharpening stars, reducing background noise, removing stars, and recombining the stars. These and other tools and scripts are available. (One of our members uses the tools in italics):
      • Background Extraction: Image Processing>Background Extraction, GraXpert background extraction, AutoBGE, or VeraLux Nox.
      • Color Calibration: Tools>Astrometry>Image Plate Solver followed by Color Calibration>Photometric Color Calibration (PCC) or Color Calibration>Spectrophotometric Color Calibration (SPCC).
      • Sharpening: Cosmic Clarity Sharpen.
      • Denoising: Cosmic Clarity Denoise, GraXpert Denoise, VeraLux Silentium, or SyQon-Prism.
      • Star removal: Star Processing>Starnet Star Removal or SyQon-Starless.
      • Star recombining: Star Processing>Star Recombination or VeraLux StarComposer.
    6. You will have to stretch your image to achieve a final image. There are many ways to do this; Histogram Transformation (HT), ASINH Transformation, Siril Curves Transformation, Generalize Hyperbolic Stretch Transformations (GHS), Statistical Stretch (Seti Astro), VeraLux HyperMetric Stretch, Siril Curves Transformation, and VeraLux Curves. One of our members does an initial stretch with VeraLux, denoises with Cosmic Clarity and then fine-tunes with Siril Curves.
    7. Fine tune your final image by adjusting the color saturation, removing excess green, or sharpening (using VeraLux HDR or VeraLux Revela) as necessary.
    8. Save the final image as a FIT, TIFF, PNG, or JPEG file.

    Seti Astro has several scripts available: Cosmic Clarity Sharpen, Cosmic Clarity Denoise, Cosmic Clarity Satellite, Cosmic Clarity Darkstar , Cosmic Clarity Superres (improve resolution), and AutoBGE.

    VeraLux also has several scripts available: Starting Point (VeraLux Workflow), Nox (background extraction), Hypermetric Stretch (Stretching), Curves (Stretching), Silentium (denoising), StarComposer (recombine the stars), Vectra, Revela (sharpen) and Alchemy (narrowband normalization and mixing).

    SyQon has two scripts available: SyQon-Starless (remove stars) and SyQon-Prism (denoising).

    A sample Siril workflow used by one of our members is here =>

    Siril Workflow SummaryDownload

    Siril References and Books

    Siril Videos

    Working with Seestar images in Siril

    Siril Videos from Deep Space Astro

    Siril Documentation & Tutorials

    Please note that FAS does not specifically recommend or endorse this or any other software, we only provide information that is generally available.

    Sirilic

    Sirilic is a Siril process that can be used to preprocess images from multiple nights. More instructions to come here …

    It is designed to run on a Windows PC with an executable download. However, there isn’t an executable for a Mac. But because it is a python program, it can be downloaded and run on a Mac. For instructions, see the video from Nebula Photos (starting at 3:00). The steps from the video are outlined below.

    1. Download the python package from Sirilic.
    2. Move it to the Desktop.
    3. Click on the “Magnifying Glass / Search” on the top menu. This will bring up a search window.
    4. Type Terminal and press return. This will open up the Terminal/Command Line window.
    5. Type cd desktop and press return to change the directory to the desktop. The next line will end with desktop %.
    6. Type pip install sirilic and press tab (not return). The rest of the command will fill in.
    7. Press return and the script will run. You will see a bunch of stuff with the message successfully installed sirilic at the bottom.

    To run Sirilic from a Mac, click on the “Magnifying Glass / Search” on the top menu. Type Sirilic and press return. Sirilic will run from the Terminal window.

    Please note that FAS does not specifically recommend or endorse this or any other software, we only provide information that is generally available.

    Astro Pixel Processor (APP)

    Astro Pixel Processor (APP) is a software package you might consider as an alternative to Siril. (More to come here.)

    Please note that FAS does not specifically recommend or endorse this or any other software, we only provide information that is generally available.

    Pixinsight

    PixInsight is a software package that seems to be gaining use among our members and in the world of astrophotography.

    Several new books have been published in 2025 on PixInsight. We haven’t read them all yet, so we don’t know which ones are better, although a few FAS members are using the book by Max Dobres.

    This page is a work in progress – much more to come.

    PixInsight Workflow / How to use PixInsight

    The functionality of PixInsight is found in many Processes and Scripts. They are technically different, but are fundamentally the tools you will use. PixInsight does not provide a specific workflow on how to use these, they are all just available for your choice.

    In general, a workflow for PixInsight involves several steps. We hope to develop a workflow used by several of our members. You may find other ways to utilize PiXinsight and its functionality. In any case, there are a few steps that are required (see below).

    1. Stack your images using the WeightedBatchPreprocessing (WBPP) script. You must load your various subframes (Lights, Flats, Biases, and Darks) to PixInsight. The script will group these subframes by filter.
    2. Your stacked image will appear dark and in linear mode. Apply the STF Autostretch routine to view the details. Use the ScreenTransferFunction to adjust the auto stretch settings.
    3. Fine-tune your stacked image by cropping the image, removing background gradients, sharpening stars, reducing background noise, removing stars, and recombining the stars.
      • Use processes and scripts such as Dynamic Crop, [DynamicBackgroundExtraction, Automatic DBE (Seti Astro), GraXpert], [Image Analysis>Image Solver, SpectrophotometricColorCalibration (SPCC)], HDRMultiScaleTransform (reduce brightness), SCNR (remove green), CreateHDRImage (improve color), [ImageBlend, PixelMath (recombine stars)], and StarReduction (adjust the number of stars).
      • You can also use these scripts from RC Astro: BlurXTerminator (sharpen stars), NoiseXTerminator (denoise), StarXTerminator (split out stars), GradientXTerminator (background extraction), and StarShrink.
      • Many processes have three icons at the bottom; Triangle (drag it to the image to execute the process), Square (click on it to execute the process on the last image), Empty Circle (preview the results of the process), and Solid Circle (apply the process globally).
      • Scrips typically have an Execute button, which will apply the process to the latest image.
      • You can drag selected process and script icons off to the right window to create and save a workflow.
    4. You will have to stretch your image to achieve a final image. There are many ways to do this; Histogram Transformation (HT), Statistical Stretch (Seti Astro), CurvesTransformation, GeneralizedHyperbolicStretch (GHS), and VeraLux HyperMetric Stretch. When stretching, you can use MaskGeneration to mask out portions of the image, so that changes only apply to just the object of interest or just to the background.
    5. Your workflow might be: stack, crop, extract background, plate solve & color calibration, star sharpen, denoise, remove stars, reduce brightness, stretch, recombine stars, and reduce stars.

    PixInsight References

    PixInsight Videos

    PixInsight Books

    • Max Dobres. PixInsight Workflows: A Step by Step Guide to Astrophotography Image Processing (Astro Imaging Guides). March 9, 2025. Amazon Paperback. Amazon Kindle. March 10, 2025.
    • Ray M.O. Palmer. PixInsight User Guide for Beginners: A Step-by-Step Manual for Astrophotography Processing, Troubleshooting & Creative Workflows. August 25, 2025. Amazon Paperback. Amazon Kindle.
    • Maya Ridell. PixInsight User Guide: Learn Professional Image Processing Techniques for Deep-Sky, Narrowband, and Astrophotography Data. July 20, 2025. Amazon Paperback. Amazon Kindle.
    • Oliver Hayes. “MASTERING PIXINSIGHT: Unlock Advanced Techniques and Enhance Your Astronomical Images Like a Pro.” June 18, 2025. Amazon Paperback. Amazon Kindle.
    • Phoenix A.D Starbridge. “PIXINSIGHT USER GUIDE: The Ultimate Step-by-Step Manual for Astrophotography Processing – From Beginner Basics to Advanced Techniques, Troubleshooting, and Creative Workflows.” June 22, 2025. Amazon Paperback.
    • Warren A. Keller. Inside PixInsight (The Patrick Moore Practical Astronomy Series). Springer. October 18, 2016. Second Edition 2018. Amazon Paperback. Amazon Kindle.

    PixInsight Documentation

    Please note that FAS does not specifically recommend or endorse this or any other software, we only provide information that is generally available.

    RC Astro Plug-ins for PixInsight

    RC Astro has several plug-ins for PixInsight and some work for PhotoShop as well.

    Please note that FAS does not specifically recommend or endorse this or any other software, we only provide information that is generally available.

    NightTime Imaging ’N’ Astrophotography (N.I.N.A.)

    N.I.N.A. is an open source application for astrophotography that you can run on your computer. Many FAS members are now using ZWO’s ASiair rather than N.I.N.A. More to come here …

    • Patrick. “N.I.N.A. Astrophotography Software Review.” AstrophotoGuru. March 13, 2023.
    • “Become a NINA MASTER and UNLEASH the FULL POWER of your astrophoto rig! Part 1.” Cuiv, The Lazy Geek/YouTube. May 29, 2025.

    Please note that FAS does not specifically recommend or endorse this or any other software, we only provide information that is generally available.

    Gimp

    Gimp is an open source (and free) alternative to Photoshop.

    Please note that FAS does not specifically recommend or endorse this or any other software, we only provide information that is generally available.

    Other Software Packages

    There are several other software packages that can be used to process your astro-photos.

    Here is some more information about several of these packages. Of course, Adobe’s Photoshop is probably the best know. However, there are other (less well known and less expensive) options.

    Please note that FAS does not specifically recommend or endorse any specific software, we only provide information that is generally available.