31mm vs 1.25 filters for asi1600pro

[AbsolutelyN]

Hi. Does anyone know if 31mm filters compared to 1.25" would help with vignetting with a zwo1600pro? I'm curious if it would make much difference or not. I know its fixable with flats but I'm interested it it woud make much difference as I get quite a bit of vignetting with my 1.25 LRGB filters. I'm not certain if it's the filters or the scope (esprit 100). Many thanks for any thoughts. 

[FaDG]

Mmmh, not sure I get the point : 31.8 is the size in mm of the 1.25" accessories. 

So I suspect you're referring to the same Product. 

Or am I missing anything? 

 

[Stub Mandrel]

39 minutes ago, FaDG said:

Mmmh, not sure I get the point : 31.8 is the size in mm of the 1.25" accessories. 

So I suspect you're referring to the same Product. 

Or am I missing anything? 

 

I think 31mm filters are  unmounted glass so slightly larger than what fits in a 1.25" ring

[Laurin Dave]

Are you using the ZWO filter wheel? If so vignetteing  with either 1.25 or 31mm easily correctable with flats..  I've used both and saw very little difference..  31mm just slightly better

 

Dave

[AbsolutelyN]

8 hours ago, Laurin Dave said:

Are you using the ZWO filter wheel? If so vignetteing  with either 1.25 or 31mm easily correctable with flats..  I've used both and saw very little difference..  31mm just slightly better

 

Dave

That's exactly what I wanted to know ... sorry if I wasn't clear enough. Yes ZWO filter wheel - probably not worth going from 1.25 to unmounted 31mm. Many thanks

[Adam J]

3 hours ago, AbsolutelyN said:

That's exactly what I wanted to know ... sorry if I wasn't clear enough. Yes ZWO filter wheel - probably not worth going from 1.25 to unmounted 31mm. Many thanks

Depends on the F-ratio of your scope, I don't see much at F5, I recently got a corrector that took that down to F4.75 and it starts showing a little more but can still be corrected. Personally I would only get the 31mm if I was planning working at F4.5 or less. 

[Allinthehead]

I used a 1600 and 1.25 filters with my Epsilon at f3.3 without issue. Do you have the filter wheel mounted directly to the camera or are you using an adapter?

[Adam J]

10 minutes ago, Allinthehead said:

I used a 1600 and 1.25 filters with my Epsilon at f3.3 without issue. Do you have the filter wheel mounted directly to the camera or are you using an adapter?

Wow really? You must see some fall off in the corners though, having done the Maths myself I don't see how it could have no effect on SNR in the corners of the image. 

[Allinthehead]

Yes there's a large light drop off but there's a significant drop off with the Epsilon regardless of filter used.

Here's a flat with an epsilon and full frame camera.

[Coriorda]

On 31/03/2019 at 23:10, Laurin Dave said:

Are you using the ZWO filter wheel? If so vignetteing  with either 1.25 or 31mm easily correctable with flats..  I've used both and saw very little difference..  31mm just slightly better

 

Dave

Correcting with flats is I think missing the point. The area affected has a lower SNR so you need to avoid vignetting happing in the first place not correct for it