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Verdict on 1.25" filters with ASI1600?

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#1 RafaelP

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Posted 07 July 2016 - 09:33 AM

Yes, another ASI1600 thread. I did a search, and couldn't find a definitive answer.
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?
Thanks!
Rafael

#2 bigeastro

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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.



#3 happylimpet

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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.


#4 happylimpet

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Posted 07 July 2016 - 02:02 PM

MasterFlat_ISO0_2.jpg

 

Flat.

 

 



#5 bigeastro

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Posted 07 July 2016 - 02:05 PM

Very nice result with 1.25" filters

#6 Jon Rista

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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. 




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