Verdict on 1.25" filters with ASI1600?
Posted 07 July 2016 - 09:33 AM
I have a F/4 Borg and would like to use my (pricy!)1.25" filters with the ASI1600. I would be using Xagyl 1.25" filter wheel, which has 19mm of backfocus.
Any thoughts or experiences on amounts of vignetting with 1.25" filters and scopes faster than F/5?
Posted 07 July 2016 - 09:47 AM
I also have an F/4 Borg and the exact same setup you indicate. I have the 77ED with the super reducer. I think it gets me to f/4. You will get vignetting but not much. You need to purchase the .8mm precise parts adapter in order to minimize the vignetting. I am at the edge of vignetting at f6.7 with the precise parts adapter. There is none on my setup, but when adjusting the filter wheel so it is perfectly centered I can see the cone drop off when I shift the filter either way. As a result I suspect that f/6 is about as low as you can go with the 1.25" filters with no or tiny vignetting.
Hope this helps.
Posted 07 July 2016 - 10:44 AM
At 12" f4.5, my Halpha flat that Im looking at drops by ~12-15% at the top and bottom edges, and by 30% very suddenly in the far corners. Should be fine.
EDIT Just remembered I have a coma corrector that makes me f4.5 , not f5. How much of a role this plays I couldnt say.
Edited by happylimpet, 07 July 2016 - 10:44 AM.
Posted 07 July 2016 - 02:13 PM
There is a small amount of vignetting with 1.25" filters with my 600mm f/4 Canon lens, but not much. I already get some vignetting with that lens anyway because I use the lens hood, which introduces some vignetting of it's own.