Λοιπον η απαντηση που πηρα απο το telescope service ηταν η εξης Actually the filters perform a very different function! The inside mod filter first of all opens a wider “window” for the camera. Normally the cameras have very little transmission in the H-Alpha line. With the mod filter you will have much more transmission in this important line. The clip filters serve to block unwanted light, much like a normal 2” filter does. For example you can get an H-Alpha or an O-III pass filter. That improves the contrast of the photo. For example the H-Alpha filter however is only useful if you ALSO have the inside mod filter at the same time! Otherwise the H-Alpha filter blocks all light except H-Alpha, and the original Canon filter blocks H-Alpha.