Vignetting with reducer?

[Tommohawk]

Hi all

Have just taken the plunge and bought a TS optics 72mm F6 Apo. First light tonight but hazy and really bright moon so not great time to test. I'm using a TS  0.79 reducer, and with Ha filters I'm getting pretty marked vignetting. Should I expect this? 

Ideally I'd be testing in LRGB but its so bright/hazy results are a bit poor.

Any thoughts please? 

[geordie85]

Personally I'd test through the lum filter and short exposures to ensure no trailing. I'd ignore the bright Moon and have as I'd only be testing for star shapes. 

Vignetting will calibrate out with good flats. 

[Tommohawk]

On ‎17‎/‎01‎/‎2019 at 22:45, geordie85 said:

Personally I'd test through the lum filter and short exposures to ensure no trailing. I'd ignore the bright Moon and have as I'd only be testing for star shapes. 

Vignetting will calibrate out with good flats. 

I agree for testing the scope performance looking at star shapes is definitely important.

But I'm still surprised at the amount of vignetting I'm getting. I agree this could be calibrated out, but I'm still surprised that its there in the first place.

So - I'd be grateful for any advice on that specific point please- should I expect vignetting with this scope and reducer?

[geordie85]

What camera are you using? If its I. Your sig, I cannot see it as I'm on my phone 

[Tommohawk]

Hmmmm. I think it's in my signature but I'm also on mobile and can't see!

Anyhow its ZWO ASI1600 with 8posn fw. I've just looked at some flats from my previous setup - a 300mm camera lens - and the vignetting is similar. So maybe its the camera/filter combo. I'm using 31mm filters and that should be free of vignetting down to F4. Allegedly.