ZWO ASI178MM-Cool Noise

[04Stefan07]

I have been imaging for many years but in the last year I have gotten into Monochrome LRGB imaging and it has proven to be that little bit more difficult.

When processing my shots of M83 from the other night I noticed there to be a lot of noise when I auto stretched the images.

I am giving PixInsight a go as I have heard many good things about the program. So far I am liking it! Combining LRGB is so easy compared with Photoshop.

See my setup in my sig. Other details

- Using SGP
- Gain from memory between 60-70, offset was lower than that
- Camera temp was between -17 and -20 C
- Focus looked great
- Each exposure is 5 minutes
- 10 Lum/10 Red/10 Green/7 Blue (I had 3 crap Blue which is why its less)
- 13 Darks
- 20 Flats per colour channel
- 20 Bias

I am planning on capturing a lot more data as I ran out of time.

A few questions I have that I can't work out
Q) Would using less blue subs give me an unbalanced colour combination?
Q) There are so many LRGB tutorials online and everyone has a different process. Do you need to do a Historigram Transformation to each channel before combining? I will need to experiment
Q) Why is there so much noise? I have a cooled camera. Maybe the gain was set too high? Exposure time was too long?

I am quite happy how M83 turned out but I am just annoyed about the amount of noise in the image.

 

Any help would be appreciated!

Thank you

[04Stefan07]

My first process in PixInsight (RGB only, trying to work out how to apply L).

Below is with the Background Neutralisation.

 

This is without Background Neutralisation and with Histogram Transformation Instead.

Edited April 19, 2020 by 04Stefan07

[tomato]

That’s a nice result, a couple of comments:

The general thinking is to use darks, flats and darks for flats for CMOS cameras rather than bias frames, I have found that the calibration results are better using this method.

I image under a Bortle 4 sky and limit my subs to 2 mins, although I use ASI 178 cameras with retro fitted Peltier coolers which cannot cool down to sub zero temps, I use the cooler to maintain a constant temp rather than forced cooling.

Edited April 25, 2020 by tomato

[04Stefan07]

20 hours ago, tomato said:

darks for flats

Thanks mate!

Did you mean Dark Flats?

[tomato]

Yes that’s right, a dark frame taken with the same exposure time as the corresponding flat frame.

[04Stefan07]

On 27/04/2020 at 01:39, tomato said:

Yes that’s right, a dark frame taken with the same exposure time as the corresponding flat frame.

No worries, I will give that a go!

Thanks.

[Gina]

That's what I do - works a treat.

[Gina]

I use an ASI178 with Peltier TEC cooling in my all sky camera, with water cooling.  I can get the camera temperature down to -20° but I use substantial thermal insulation of the camera body.  Water cooling is significantly more efficient at removing heat from the hot side of the TEC.  I could only get to around freezing with air cooling though that was in warmer weather.

[04Stefan07]

I was going over my data and camera settings from that night trying to see if there was anything I did wrong. Looking at the camera settings in SGP I noticed the offset was on maximum which may have been the cause for the extra noise and issues I was having. I may have put it on max to test something and forgot to turn it down.

A few nights back I went out again, setting the telescope on M83 to give it another crack. Some changes.

- Decreased exposure from 300s to 120s
- 176 minutes of data (down 9 minutes from last time, not by choice but time!)
- Used Dark Flats instead of Bias frames
- Now with more experience in PixInsight did a few different things

The only bloody problem is capturing on different nights may yield various results due to weather, atmospheric conditions and plane trails. Because of this we can never get an accurate result when comparing processing photos from night to night.

Here is the result (would like to get more data on it though). Feedback is much appreciated!

I find the first images I took the galaxy looks more full, or is it just my eyes?

Edited April 29, 2020 by 04Stefan07

[04Stefan07]

I think I have finally nailed it.

After watching many tutorials and creating my own workflow I have come up with the below. Still a lot more to explore with PixInsight but am happy with the result.

I found the key is to make the L channel a little brighter for the detial to pop.