Artifacts during processing

Jan 19, 2021
9
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During my initial experience processing with PI, I have come across some artifacts that have not presented themselves during my utilization of other processing software programs. I recently started using PI after a year of using Startools. In the link below are: my stacked and callibrated image of M42, along with a processed image from PI. After performing DBE, I am seeing bright red and blue dots all over the image that I have never seen before and were not apparent on any subs or stacked image.

Prior to DEB, I am cropping and doing background neutralization along with color calibration.

My only experience with processing has been with Startools, so I processed using the same data and do not see these red and blue artifacts on the image. Is there something I may be doing incorrectly? I have been following the instructional videos from Harrysastroshed and have been very pleased with what PI offers and the results. I am sure there is a reason these are showing up, but after speaking with a couple folks in my astronomy club that use PI, we have not been able to pinpoint the source.

OneDrive link below:



Any insight? I appreciate any feedback and am very excited to fully incorporate PI...what a powerful tool!

Thanks

Aaron
 

pfile

PTeam Member
Nov 23, 2009
6,170
180
were both png images calibrated and stacked in DSS and then processed in PI/Startools?

or did you calibrate/align/stack the PI image in PI?

what kind of camera is this?

rob
 
Jan 19, 2021
9
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Sorry Rob. I stacked and calibrated the images just once. I then processed the same image on two separate occasions about a month apart.
 

pfile

PTeam Member
Nov 23, 2009
6,170
180
ok i was just trying to understand if the starting integration was the same. and also if the camera was uncooled, but that one looks to have a thermoelectric cooler.

to the first order the artifacts look like hot pixels. in ST did you do any kind of cosmetic correction step or noise reduction step?

rob
 
Jan 19, 2021
9
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Yes, I did noise reduction in Startools. I do not recall the exact step as the processes in Startools area little confusing to me. I, too, thought they were hot pixels at first but there seem to be way more here than what I have seen in the past when I do my darks. I also noticed that there are Blue and Red dots throughout the image. At first I only noticed the red dots.
 
Jan 19, 2021
9
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I am processing another image tonight and am noticing the red dots when I first apply the ScreenTransferFunction to begin the Background neurtalization after I crop. I thought it was after DBE, but they are noticeable right away.

Thank you, by the way, for responding and discussing it with me.
 
Jan 19, 2021
9
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This is roughly the process I have been following. I also did the SCNR process (not sure if it was before or after color calibration).

Crop - DBE - Background Neutr + Color Cal - MLT noise reduction - Histo Stretch - Curve trans - Saturation boost
 

pfile

PTeam Member
Nov 23, 2009
6,170
180
no problem - i havent had a chance to download your file yet but hopefully later this evening i can look at it.

rob
 

pfile

PTeam Member
Nov 23, 2009
6,170
180
i did take a look at the autosave file - something has definitely gone wrong in DSS as there are 'hot pixels' in the red and blue channels of the image and 'cold pixels' in the green channel. but whatever these artifacts are, they are larger than single pixels. they don't seem to be actual hot/cold pixels. i wonder if there was some problem with the registration of some number of the input frames.

the stretch in PI is just a little more aggressive than the ST stretch and so you can't really see these artifacts as well in the ST image, but they are there...

rob
 
Jan 19, 2021
9
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Thanks Rob. I went ahead and took another batch of darks in case they were bad. I am pretty new at this, so I was wondering what you would recommend I do as a next step? I obviously need to try PI for stacking and calibration. I have had a great experience with my trial, so I no doubt will purchase (trial ends in a week or so). It sounds like, based on what you saw, the dots have probably been in my images all along, I just have not seen them. Is this a possibility?

I have included a dark, flat and dark flat for your review if you are so inclined to take a look. I also included a dark FITS frame where the hot pixels are visible. Time permitting, I will do a stack of M 42 tonight or tomorrow in PI and see if this yields an image without the dots. Any other suggestions?

Again, many thanks for your insight. I am impressed with PixInsight and now fully understand what everyone has been raving about. Now that I have a year under my belt in this hobby and overcome most of the beginner obstacles, I am more confident in my ability to implement PI in both stacking and processing.

Aaron