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Posted

Hi,

Absolutely love the Affinity Suite of packages and as I am just getting into astrophotography I was keen to use the Astrophotography stacker in Affinity Photo. However, I think I have come across what I think is a bug which means it does not processes the .fit files from my ASI 071 camera. I wonder if this is the reason why some others have reported similar issues.

All the fit files in their native form and subsequent stacked images have a lurid green cast to them, and I have tried using James' macros to neutralise the colour balance, which works to some extent but I then noticed my first attempt to image the Rosetta Nebula showed none of the red nebulosity I was expecting to see. Initially, I thought this might be down to a lack of overall exposure time (2 x1h stacks), due to the location of my telescope, but I have since ran a 6h stack of the Heart Nebula, and the faint red glow of the nebula I saw on the preview images in the ASI AIR app is conspicuous by its complete absence. 

I have since noticed that on inspection of the exposure histograms for the light flat images taken this morning that the Green and Blue channels are evident, but there is no red-channel curve. This is consistent throughout all the images I have taken. I have tried all the raw settings possible and this does not resolve the issue, but instead mis-assigns the B & G channels incorrectly.

This may be the reason why other users and myself have seemingly ran into this problem and it is interesting that these other users have successfully stacked their images in other software (I haven't yet tried) and would explain the absence of any nebulosity in any of my images or stacks so far.

I've enclosed a screenshot taken of one of the 'white' flats at the pre-stacking stage, to illustrate the point. AS you will see it has a delightful hue to put British Leyland Java Green to shame.

I would be happy to share a selection of fit files, for anyone trying to reproduce this bug. 

Equipment used:

ZWO 071 Pro Camera, ASI AIR Plus Controller, Affinity Photo V 2.6.2 on Mac OS X Sonoma 14.7.3

Many thanks in advance,

 

Henry

 

Screenshot 2025-04-07 at 07.21.23.png

Posted

Can you upload  a few sample raw files?

Mac mini M1 A2348 | MBP M3 

Windows 11 - AMD Ryzen 9 5900x - 32 GB RAM - Nvidia GTX 1080

LG34WK950U-W, calibrated to DCI-P3 with LG Calibration Studio / Spider 5 | Dell 27“ 4K

iPad Air Gen 5 (2022) A2589

Special interest into procedural texture filter, edit alpha channel, RGB/16 and RGB/32 color formats, stacking, finding root causes for misbehaving files, finding creative solutions for unsolvable tasks, finding bugs in Apps.

I use iPad screenshots and videos even in the Desktop section of the forum when I expect no relevant difference.

 

Posted

Hi NotMyFault,

Sorry, of course - should have thought of doing that from the outset.

 

Here are a couple of sample files:

One is Flat, so should be a medium exposed neutral grey / white image and the other is one is a 3 minute exposure of the Heart nebula (IC 1805).

IIRC there was a faint hint of crimson towards the top left corner of the frame.

 

Hope they are of some use. Let me know if you need any more files. These are pretty much representative of the output I am getting from all the raw .fit files generated by the ASIAir.

The corresponding JPEG thumbnails are also included to try and give some indication of what I was hoping to have seen..

KR

 

H

Light_IC1805_300.0s_Bin1_20250406-213033_0001_thn.jpg

Flat_40.0ms_Bin1_20250407-065206_0001_thn.jpg

Flat_40.0ms_Bin1_20250407-065206_0001.fit Light_IC1805_300.0s_Bin1_20250406-213033_0001.fit

Posted

Thanks for your files.

When I open the files in Photo / Astro stack, I get a greenish rendering initially.

This can be easily adjusted by the level adjustment which was added by default, selecting the channels and using histogram, scope panel and info panel.

  • reduce output level to mute color channel
  • reduce white level to boost a color channel
  • have color pickers placed on background and highlights to ensure a uniform result.
  •  

Screenshot 2025-04-07 at 20.30.26.png

Screenshot 2025-04-07 at 20.30.12.png

Mac mini M1 A2348 | MBP M3 

Windows 11 - AMD Ryzen 9 5900x - 32 GB RAM - Nvidia GTX 1080

LG34WK950U-W, calibrated to DCI-P3 with LG Calibration Studio / Spider 5 | Dell 27“ 4K

iPad Air Gen 5 (2022) A2589

Special interest into procedural texture filter, edit alpha channel, RGB/16 and RGB/32 color formats, stacking, finding root causes for misbehaving files, finding creative solutions for unsolvable tasks, finding bugs in Apps.

I use iPad screenshots and videos even in the Desktop section of the forum when I expect no relevant difference.

 

Posted

Hi NotMyFault - 

Thanks for your prompt reply. Sorry, I've not replied back sooner.

I had a relook at the stacks again. Clearly I have a lot to learn and need to work on the images in the way you describe  to try and see if there is anything I can pull out of them, but regarding the greenish cast, one  observation I have made is that when I inspect the files pre-stacking, the R, G and B channels are all present for the Light, Bias and Dark Frames, but all the Flat frames contain no R channel data that I can see - the pixel inspector consistently registers 0 across all the frames. I've appended some screenshots of what I am seeing currently.

This makes me think it could either be an issue with either the way the ASI Air has generated these flats, or that these data from the R channel are not being captured or recognised when the .fit files are being imported at the file selection point in Affinity photo that is specific to this Frame type (ie Flat).

I can't but help think that its related to the way affinity photo handles the flat frames, as I have just inspected the same .fit file in ASTAP and there are definitely 3 peak in the histogram (screenshot appended, although I suspect the Red channel peak is the lower one of the three - but still not so low that I would expect it to register a 0 throughout the whole frame in affinity photo.

Maybe I am overthinking things here, but it just seems strange that all the pre-stacked histograms look acceptable for the light / dark and bias frames and its just the flat frames where everything goes wrong.

Here are some additional screenshots of the pre-imported .fit files when you look at them with the inspector. Sorry - can't show the RGB values at same time - but ALWAYS 0 for red on the entire Flat frame.

Kind regards,

 

Henry

Screenshot 2025-04-10 at 07.58.49-RedChannel-Light.png

Screenshot 2025-04-10 at 07.58.54-RedChannel-Bias.png

Screenshot 2025-04-10 at 07.58.59-RedChannel-Dark.png

Screenshot 2025-04-10 at 07.59.04-RedChannel-Flat.png

Screenshot 2025-04-10 at 08.08.45-ASTAP-Flat.png

Posted

Unfortunately I’m no specialist for Astrophotography or four specific Camera vendor products. I suspect the issue is on the camera side, not Affinity Photo.

i would recommend to visit the forums from zwoastro.com, stargazers, … to get support from peers.

Occasionally James Ritson steps into this forum, and might step into this thread, too.

Mac mini M1 A2348 | MBP M3 

Windows 11 - AMD Ryzen 9 5900x - 32 GB RAM - Nvidia GTX 1080

LG34WK950U-W, calibrated to DCI-P3 with LG Calibration Studio / Spider 5 | Dell 27“ 4K

iPad Air Gen 5 (2022) A2589

Special interest into procedural texture filter, edit alpha channel, RGB/16 and RGB/32 color formats, stacking, finding root causes for misbehaving files, finding creative solutions for unsolvable tasks, finding bugs in Apps.

I use iPad screenshots and videos even in the Desktop section of the forum when I expect no relevant difference.

 

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