M33 image issues

[Iem1]

Afternoon guys,

just looking for opinions on what may be the cause of a couple of issues in my M33 Triangulum Galaxy image.

The image consists of around 2 hours of 30 second subs, ~30 Flat frames, ~20 Bias frames (Tried 20 darks to see if these were the issues, but it did not seem to make any difference) and was taken with a WO Z73 + a astro modified Canon 600D all on a SGP

There is a grey haze in the bottom left corner, and two distinct bands just about visible too, which become very prominent unless careful in processing.

Any ideas what the issue could be? I am going to remove the flat frames next and run just bias, see if they are perhaps impacting negatively.

It was a moonless night, only thing that grey haze could potentially be is a bit of light pollution. I was under a dark sky (Bortle 3-4) but there was a building with visible pollution on the other side of the hill, perhaps it was captured -.- Can not figure out how to remove the issues, but this is where I got to. Its a shame as I thought the image was shaping up nicely (by my standards anyway!)  

(I did not do any noise reduction yet, just basic stretching)

 

Stacked tif

Autosave.tif

[vlaiv]

That sort of looks like amp glow, but could be a light leak as well.

What does your master dark look like?

Do yo use viewfinder cover when taking your subs?

[bottletopburly]

Nice image quite a bit of walking noise , are you able to dither with your setup ? 

[Iem1]

4 hours ago, vlaiv said:

That sort of looks like amp glow, but could be a light leak as well.

What does your master dark look like?

Do yo use viewfinder cover when taking your subs?

Not for the light frames, but ironically this was the first night that 'closed' the 600D's screen, so there was no bright display light present through the imaging!

I was not planning on taking dark frames as I have read they are not necessary for my camera, so I was going to try without. But I decided I may aswell just incase, but I took the dark frames after I took the flat frames, around 05:30 when is was fairly bright. I covered the scope with jackets and anything I had to hand hoping it would help, but I am sure they are not ideal. Also, my intervalometer was fragging out while taking darks...So they are 33 seconds long compared to my 30 second exposures.

These are the master calibration frames

Master Dark

MasterDark_ISO800_33s.tif

Master Flat

MasterFlat_ISO800.tif

Master Bias

MasterOffset_ISO800.tif

50 minutes ago, bottletopburly said:

Nice image quite a bit of walking noise , are you able to dither with your setup ? 

Thanks! i was quite pleased with the results considering itis 30 second subs!

Unfortunately not, at least not properly. I am using an unguided system and limited to short exposures, so I cant dither between frames efficiently. Though i may try some periodic dithering soon, every 20 - 30 mins or something. See if that makes a difference. 

[alacant]

Hi

Looks fine to me. The data is ok but could easily be improved.

The calibration frames are not party to the light stain (English?) bottom corner so this must have been introduced when you took the frames in the field. Make sure the viewfinder is covered.

The banding is present in the dark frames and there is significant walking noise. With a 600d, lose the dark frames. The image will be cleaner that way. Be sure to dither between each frame and stack with a clipping algorithm as this will also help minimise the walk and bands. Bin the image before processing.

Here is a quick 5 minutes in StarTools:

 

 

 

Edited August 12, 2021 by alacant
bad translate

[vlaiv]

I can't seem to find anything in calibration files so it looks like it is neither amp glow nor light leak.

Judging by stack structure - it is most pronounced in Red channel - this leads me to believe it is related to light pollution, but it's not light pollution itself as it's not linear gradient (or close to linear).

There is component of this that is linear gradient, but there is something else.

Can you examine your subs, I think that one or few subs might be having a passing high altitude cloud in that spot.

[Iem1]

Good work Alacant!

I have just managed to remove the glow in PS, but I will run another stack minus the dark frames, repeat steps to remove glow again and see where I am at with it.

And yes, the walking noise is worse than usual in this image. Is that reflective of dropping from 60 to 30 second subs perhaps?

I can not wait to get an a guiding system in place along with a more suitable mount, will hopefully see a big difference in quality with the extra tools at hand.

Thank you vlaiv!

Appreciate you having a look, Il run through each sub and keep an eye out for issues

 

All the help is much appreciated as always

[alacant]

5 minutes ago, Iem1 said:

Is that reflective of dropping from 60 to 30 second subs perhaps?

If there were more of them and you didn't dither, yes.

 

7 minutes ago, Iem1 said:

can not wait to get an a guiding system in place

Or perhaps just get a proper astro processing app meanwile?

Cheers

[Iem1]

I gave startools a try but I found it to be very slow on my laptop, PS/GIMP/SirL work quick and easy.

But I think I will give startools another go, it seems to be highly recommended, I just need to get used to it and spend time on it.

Il post my results here soon

[alacant]

21 minutes ago, Iem1 said:

startools a try but I found it to be very slow

Did you try the latest version with GPU support? Even on a modest box running vanilla Ubuntu, it flies.

But yes, Siril for Stacking. A must have:)

Cheers

 

Edited August 12, 2021 by alacant

[Iem1]

I will look into that, be great if I can make it a bit smoother

Here is where I got in PS, will give it a shot in star tools soon too! Had to work around those two prominent bands, one of them cuts straight the galaxy and it shows, but its as good as i am going to get it I think

 

[alacant]

20 minutes ago, Iem1 said:

work around those two prominent bands,

Remove them using Siril first.

You'll probably find that Siril will do a better job on both the background and the development. Maybe reserve gimp/ps simply for cosmetic stuff after the main event?