Issues with Colour and Wipes

Questions and answers about processing in StarTools and how to accomplish certain tasks.
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Ricker
Posts: 10
Joined: Sat Jul 04, 2020 11:47 am

Issues with Colour and Wipes

Post by Ricker »

Hi, I seem to have this issue and I cannot find a satisfactory way forward.

I have taken some L (60x30s), R (30x60s), G (30x60s), B (30x60s) and Ha (15x120s) frames and composite them in Startools. They have been dark subtracted and a flat field applied from within Siril, using the SirilIC tool.

When I apply the wipe the L and Ha frames look good, but the RGB frams still seems to have a green colour bias to it where this seems to disappear toward the corners, in a vignetting type pattern, see file in link.

I do get a good colour frame if I wipe with an uncalibrated preset but this feels like I should not need to do this.

Am I just expecting too much?

I have included a link to my stacked frames below.

Can anyone give me any advice? Please let me know if you need more information.

https://drive.google.com/drive/folders/ ... sp=sharing

Many Thanks

Rich
almcl
Posts: 218
Joined: Wed Jan 21, 2015 7:15 pm
Location: Shropshire. UK

Re: Issues with Colour and Wipes

Post by almcl »

The R frames don't seem to have made it on to your Google Drive page, Rich?
Skywatcher 190MN, ASI 2600 or astro modded Canon 700d, guided by OAG, ASI120, PHD2
Ricker
Posts: 10
Joined: Sat Jul 04, 2020 11:47 am

Re: Issues with Colour and Wipes

Post by Ricker »

Thanks for letting me know. I have now added the R data.

Rich
almcl
Posts: 218
Joined: Wed Jan 21, 2015 7:15 pm
Location: Shropshire. UK

Re: Issues with Colour and Wipes

Post by almcl »

I had ago with your data (thanks for posting it) and, just as you say, the original wipe after cropping to get rid of some of the artefacts does show up with a green cast. And, again as you mention, the eventual result of a very quick process produces a nice image:
NewComposite.jpg
NewComposite.jpg (244.65 KiB) Viewed 914 times
Looking at the original fits files, there seem to be a lot of artefacts common to each of the five. Now I know nothing of Siril (apart from that I couldn't get it to work on my Windows PC) but it looks as though the calibration frames may not be doing too good a job. Did you have flats for each filter? Or just one set for all? If the latter, might the flats be causing the casts?

Hopefully someone with more knowledge of Siril specifics will chime in.

Here's what the individual L file looked like:
Lum.jpg
Lum.jpg (136.74 KiB) Viewed 914 times
The G was very similar:
G.jpg
G.jpg (122.35 KiB) Viewed 914 times
Skywatcher 190MN, ASI 2600 or astro modded Canon 700d, guided by OAG, ASI120, PHD2
Ricker
Posts: 10
Joined: Sat Jul 04, 2020 11:47 am

Re: Issues with Colour and Wipes

Post by Ricker »

It was separate flats and dark flats for each filter and appropriate dark for the lights.

I will have a closer look again this afternoon when the kids are preoccupied.

Thanks for trying the data.
Ricker
Posts: 10
Joined: Sat Jul 04, 2020 11:47 am

Re: Issues with Colour and Wipes

Post by Ricker »

Having investigated somemore, I can improve the colour wipe by selecting the basic wipe preset and setting Syntetic Dark/Bias to Adaptive Multi-Axis Bias Conservative ad Dark AnomlyFilter to 4. Does this suggest the issue is with my dark frames?

The darks used were created a while ago. As the camera is cooled and the darks are a function of temperature, gain and offset I thought that these would remain constant over time.
almcl
Posts: 218
Joined: Wed Jan 21, 2015 7:15 pm
Location: Shropshire. UK

Re: Issues with Colour and Wipes

Post by almcl »

It might be worth stacking say the L frames without darks and seeing if this makes a difference? Also without flats but with darks.

I don't know enough about Siril to say whether one of the calibration stacks could be causing the issue, but perhaps worth a look?
Skywatcher 190MN, ASI 2600 or astro modded Canon 700d, guided by OAG, ASI120, PHD2
Ricker
Posts: 10
Joined: Sat Jul 04, 2020 11:47 am

Re: Issues with Colour and Wipes

Post by Ricker »

Thanks again for the advice. I am currently working through those steps to see if I can highlight the issue.

Useful to have a second opinion.
Ricker
Posts: 10
Joined: Sat Jul 04, 2020 11:47 am

Re: Issues with Colour and Wipes

Post by Ricker »

Does wipe work on the combined chrominance or on each image making up the chrominance frame? RGB combined or R then G then B?
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