Category: Hardware

Worldwide coma correction exercise

Introduction

What is coma and why needs to be corrected. Coma is a special type of an optical aberration. It’s mainly visible in the astrophotography – the stars are deformed into comet-like shapes:

Fast Newtonian telescopes suffer from comatic aberration, mainly in the corners of the photos. These telescopes are nowadays very popular between amateur astrophotographers just like me, because they offer the best price/aperture ratio. There is easy way how to suppress the comatic aberration – coma correctors. There are many coma correctors on the market, but there are just a few published reviews or comparisons between them. Therefore I decided to perform the comparison myself. Quite big collection of coma correctors has assembled in my drawer ready to be tested:


Triangular stars

Maybe someone with newton telescope experienced the same problem as I did. After cleaning primary mirror of my newt, BTW here is a nice tutorial how to do it, I noticed that the brighter stars have triangular shape. After some googling I found the indications that I have pinched primary mirror. Fortunately, it was just elastically deformed by the rubber clamps. When I placed the mirror back I overtightened the screws, therefore the mirror was not reflecting brighter stars properly.

Triangles