Artefacts in stacke...
 
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Artefacts in stacked image  

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(@scott44)
White Dwarf Customer
Joined: 2 years ago
Posts: 19
June 11, 2019 17:00  

Hi - I am using an ASI294MC Pro and have stacked 30 light frames, with darks, flats and bias.  I am getting small lines in red, blue and green across the image.  See attached (its a low quality jpeg as the site didn't allow a higher quality tiff).  I thought it may be hot pixels and have created a bad pixel map and also used sigma clipping in integration but no improvement.

Have tried DSS on same data using its recommended settings.  The result does not show these artefacts.  Any ideas?

APP artefacts1
This topic was modified 2 years ago by Mabula-Admin

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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3861
June 11, 2019 17:54  

Yeah does look like hot pixels. How did you create your bad pixel map exactly? Also, it might be nice to see like 10 frames, 10 darks, 10 flats and 10 bias via wetransfer.com I could have a look at the data and see if something is up. You can mail the link to vincent@astropixelprocessor.com


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(@scott44)
White Dwarf Customer
Joined: 2 years ago
Posts: 19
June 11, 2019 18:32  

Thanks Vincent.  I'll arrange the transfer as requested.  I may have been naive in that I simply selected the option to create a BPM in the calibration stage.  I'm relatively new to this and I'm sure its user error.  I should say I have created other images with the same setup and process in APP and this is the only one so far that showed this issue.


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3861
June 11, 2019 20:10  

Ah, well that probably means it's related to the data itself (if you did the same with the other images). Usually it shows up pretty quickly if we look at the data, so hopefully I can give you an answer very soon after that.


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3861
June 11, 2019 21:04  

Mmm, I get server errors from wetransfer at the moment. I am on a camp-site, so that might cause a few issues. Do you have it on Google Drive maybe?


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(@scott44)
White Dwarf Customer
Joined: 2 years ago
Posts: 19
June 11, 2019 22:33  

No - sorry.  No rush - enjoy your camping!


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3861
June 11, 2019 22:38  

Thank you. Well, if you could put them in a zip file, that might help maybe..


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(@scott44)
White Dwarf Customer
Joined: 2 years ago
Posts: 19
June 11, 2019 23:03  

On its way.  Reduced the size by 50% so hopefully more luck.


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3861
June 11, 2019 23:53  

Excellent, thanks a lot! Almost there. I'll have a look at it tomorrow.


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3861
June 14, 2019 11:04  

Sorry, wifi troubles overhere. Will get to it today!


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3861
June 14, 2019 11:50  

So I'm seeing the same issue indeed. The darks and bias seem ok, bpm as well. Flats can be a point of some issues sometimes, especially if the way they are taken isn't optimal. How do you make them? I see the exposure time is just 0.02 seconds, which is really fast, usually people use a less bright source of light and longer exposure times.

I tried turning the flats off and then the background is suddenly filled with these things. So it seems a weird pattern in the data, I'm now trying to find out if it's indeed within the data. For that, it would be interesting to see what DSS made of it, could you send the result of that to me at vincent@astropixelprocessor.com?


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3861
June 14, 2019 12:23  

Allright then, upon further testing.. I switched off all calibration frames as playing with the flats didn't make it better. Doing this made the problem go away and I just see a few hot-pixels causing stripes. So this seems to point to an issue with either the bias or darks. Difficult one to diagnose, I might have to get some help from Mabula but he's abroad at the moment so that might take a while (@mabula-admin).


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(@scott44)
White Dwarf Customer
Joined: 2 years ago
Posts: 19
June 14, 2019 20:50  

Hi Vincent - thanks for your efforts, apologies was at work so couldn't respond sooner.  I'll send you the DSS stack to deepen the puzzle 😉  OK for it to take awhile - I'll be travelling anyway so won't have access to APP for next week or so.


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3861
June 15, 2019 10:33  

Mm, the DSS result has a darker background so maybe it doesn't show then. Difficult still. 🙂 I do like APP's cleaner result for the galaxy. Will be continued when Mabula is back.


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(@scott44)
White Dwarf Customer
Joined: 2 years ago
Posts: 19
June 16, 2019 13:37  

Thanks Vincent


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(@mabula-admin)
Universe Admin
Joined: 5 years ago
Posts: 2728
June 29, 2019 14:02  

Hi @scott44 and @vincent-mod,

Thank you Callum, for bringing this issue to our attention.

Can one of you give me a link for download of the data so I can study the data? I will then have a look as soon as possible 😉 to see if I can pinpoint the exact cause of your colored stripes.

Apologies Callum for the delay in solving this issue.

Mabula


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(@scott44)
White Dwarf Customer
Joined: 2 years ago
Posts: 19
June 29, 2019 16:39  

Thanks Mabula.  Am away from home today so will send tomorrow evening.  Much appreciated.  Have processed some other data on different targets since from my ASI294MC Pro and Nikon 3100 without any issue so unclear what can be causing it with that dataset.


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(@scott44)
White Dwarf Customer
Joined: 2 years ago
Posts: 19
July 1, 2019 20:58  

Hi Mabula, Apologies got back late last night.  What email address can I use for We Transfer to get the files to you?  Thanks Callum


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(@backroadrider)
Brown Dwarf Customer
Joined: 3 years ago
Posts: 7
July 4, 2019 14:20  

Hi,

I am having a similar problem with an ASI071MC Pro camera as you can see in the screenshot of the attached "overstretched" image.

The problem appears to be in the Master Dark file. I have attached screenshots of the stretched master dark as well as a typical dark sub from the stack used to make the master dark. I am happy to send the actual fits files; and any thoughts would be appreciated.

Thanks,

Steve

Boosted Dark Subframe
Boosted Master Dark
Boosted Image

 


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3861
July 4, 2019 17:53  
Posted by: Callum Wingrove

Hi Mabula, Apologies got back late last night.  What email address can I use for We Transfer to get the files to you?  Thanks Callum

Hi Callum, I would use mabula@astropixelprocessor.com as I'm currently not able to use my computer during a move abroad (again, yes I know.. 😉 ). @Mabula-admin


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