Collimation

Reflecting telescopes (containing mirrors) are great for beginners and experienced astronomers. They enable telescopes to have larger apertures with less size and weight than comparable-diameter refracting telescopes (containing lenses). One of the disadvantages of reflectors is that they have to be collimated from time to time. This is the process of aligning the mirrors to give you a sharp image. Fortunately, it doesn’t have to be done too often – usually only when your view starts to get a little fuzzy. Depending on your telescope’s construction and usage, collimation may need to be performed before each use, once per year, or maybe never. Some sources suggest performing collimation at the start of every viewing season.

The tools for collimating a telescope are rather simple. Most, if not all, reflectors come with a collimation cap. Many amateur astronomers purchase laser collimation tools that make the process a little easier. You might need a screwdriver as well.

Collimation is not necessarily a complicated process – although it could take a half hour or so. In all cases, you should always follow the instructions that come with your telescope. You might also find instruction online from your telescope supplier (see the videos below from Orion). And it doesn’t hurt to recruit someone who has some experience and can help you.

The very general process is:

1. Position the telescope horizontally.
2. Align the secondary mirror first.
3. Align the primary mirror next.
4. Check alignment and repeat steps 2 and 3 as necessary until successful.