M31 with Sharpstar 61EDPH ASI1600mono

[Spacecake2]

wow... so much detail 

The full image took 1 minute to load, but it felt like 3!

Question: What was the total exposure time?

[Tommohawk]

Thanks. Posted this a while back, but post #1 shows: 14x300s Ha, 90x60s R, 56x60s G, 63x60S B

So I think thats 279 minutes total - -but you might want to check the maths!

[Adam J]

On 16/01/2020 at 22:32, vlaiv said:

Apart from the fact that color balance is quite a bit off, and that you have issues with background and red star halos - very nice image indeed. So let's address some of those issues.

First off, in order to control star size you should really use lum - but not any lum filter. If your scope is not well corrected - and by the looks of it and your story - it seems to be not so well corrected - you need to use "special" lum filter - astronomik L3 (I think, let me check that) - indeed it is L3:

It will prevent bloating from both blue side and also from red side of things as it finishes rather early on both sides of spectrum. Bloating is due to unfocused light - and most of it will come from either sides of spectrum. Cut those "wings" and you have yourself smaller stars.

Since their RGB filters also follow this - L3 curve, maybe swap red as well?

Now for background. I'm seriously surprised that you have such background on ASI1600 cooled version. I've seen such background before and it almost always comes from CMOS sensors that are not cooled and as far as I gathered - it is related to offset and calibration.

What offset did you use, and how did you calibrate image?

I have done exactly this on my ASKAR 180 vlaiv but place the 2inch L-3 filter in line with my 1.25 filter wheel with baader LRGB. It effectively clips down the red and blue filters while keeping everything para focal. 

Edited January 15, 2021 by Adam J

[Tommohawk]

3 hours ago, Adam J said:

I have done exactly this on my ASKAR 180 vlaiv but place the 2inch L-3 filter in line with my 1.25 filter wheel with baader LRGB. It effectively clips down the red and blue filters while keeping everything para focal. 

Now why didn't I think of that!