Request you to help critique the processing technique and final output of the image. Posting the starless version as I am particularly concerned that there is a lot of "scratches" or scratchiness in the image especially in the dark areas. More context about the image: Link to stacked file: https://drive.google.com/file/d/1qcc0CJ5-LxDEUCM-99kirw6ibRPFTwLC/view?usp=sharing- 45 light frames of 90s exposure
- 10 dark frames of 90s exposure
- I did not use flat frames at this time - There were two very small dust spots which I conveniently filled using context aware in post processing! Of course, not planning to make it a habit.
- Camera at 390 gain and 2 degrees C cooling. I used to cool down till -15 deg C, but that would result in a central area of frosting. Based on recommendations from other members, I tried drying the dessicant tablets of the camera, then slowly cooling in steps of 5 degrees but it would not go away. So I am staying at 2 degrees C
- Filter used: Optolong L Extreme
- Equipment used: ASI294MC Pro Camera, WO 71GT APO, WO 50mm guidescope, ASI120MM guidecam, ASI AIR, iOptron CEM40. No dithering during guiding
- Siril used for post processing. Sequence is:
- Background extraction (add dithering selected) - The scratchiness started becoming evident right at this stage itself.
- Curves transformation
- Noise correction (Tried all combinations of 'individual channels' and secondary denoising using D3D and other techniques, still does not remove scratchiness)
- Remove green noise
- Median filter
- Deconvolution
- Extract Ha and O3 from RGB image using pixel math, followed by another pixel maths to get back the colour image (pretty sure this step does not have anything to do with the scratchiness).
Request your critique on:1. Potential cause of the scratchiness and how to remove it 2. Quality of post-processing (curves, saturation, final look, etc) 3. Please feel free to provide any other inputs Thanks for your feedback and helping me learn more.  |
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Hi,
My guess on the "scratchiness" is that it is due to the limited integration time you have : just a little bit more than 1 hour of data.
This seems insufficient to reduce the noise that may be due to light pollution in the area from where you take pictures.
You should try to put 5 additional hours into that, and stack with this amount and see if the noise reduce ;-)
By the way, when zooming in the picture, the structure of the noise seems to be linked to the "abuse" of a noise reduction algorithm. But maybe it's compression on the image posted ?
Hope this helps
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Hi,
please share the RAW file after the integration…
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Start to dither and your "scratches" will most likely be gone (I assume the darks match your lights). And I would recommend to capture more data and of course do flat correction.
Rob
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Fabio Acquarone:
Hi,
please share the RAW file after the integration... EDITED. I realized the attachments wont work due to large size. Sending a Google Drive link to download. Link: https://drive.google.com/file/d/1jrzDem9nyxOaiSNGZQkKnWVK8NRsVW_r/view?usp=sharing |
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Fabio Acquarone:
Hi,
please share the RAW file after the integration...
EDITED. I realized the attachments wont work due to large size. Sending a Google Drive link to download.
Link: https://drive.google.com/file/d/1jrzDem9nyxOaiSNGZQkKnWVK8NRsVW_r/view?usp=sharing
Unfortunately the image is processed...  |
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Die Launische Diva:
Fabio Acquarone:
Hi,
please share the RAW file after the integration...
EDITED. I realized the attachments wont work due to large size. Sending a Google Drive link to download.
Link: https://drive.google.com/file/d/1jrzDem9nyxOaiSNGZQkKnWVK8NRsVW_r/view?usp=sharing
Unfortunately the image is processed...
My apologies! I just restacked using only the darks and lights to confirm it is unprocessed. Here is the latest link. Thanks and appreciate all your help! I also realized I had ~80 light frames and ~30 dark frames. Much more than the exposure I originally thought! Link: https://drive.google.com/file/d/1qcc0CJ5-LxDEUCM-99kirw6ibRPFTwLC/view?usp=sharing |
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Die Launische Diva:
Fabio Acquarone:
Hi,
please share the RAW file after the integration...
EDITED. I realized the attachments wont work due to large size. Sending a Google Drive link to download.
Link: https://drive.google.com/file/d/1jrzDem9nyxOaiSNGZQkKnWVK8NRsVW_r/view?usp=sharing
Unfortunately the image is processed...
My apologies! I just restacked using only the darks and lights to confirm it is unprocessed. Here is the latest link. Thanks and appreciate all your help! I also realized I had ~80 light frames and ~30 dark frames. Much more than the exposure I originally thought!
Link: https://drive.google.com/file/d/1qcc0CJ5-LxDEUCM-99kirw6ibRPFTwLC/view?usp=sharing
No worries! At first glance, it seems you have walking noise residuals. The lack of flats makes life harder too... So, if you have more lights and darks, let's hope that at least the walking noise residuals will be suppressed!
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It's not a bad start, you just need more exposure time and proper calibration frames.
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@akshay87kumar If you're looking to get less noise (scratches), dithering and longer integration times are the best first line of defense. For the current image tho, maybe crop it out so that the brightest parts (less noisy) and flat artifacts are gone. I had a go and deliberately cropped out the two most obvious dust motes + the weird side vignetting. Here's what I got. Draft_HOO.jpgDraft_RGB.jpg |
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@Joon Ren Thanks for editing and sharing the images. I would certainly like to learn more about post-processing techniques - I am amazed to see I have left out so much of detail in my processing!
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You'll get there. Don't forget that some of us, myself included have a photo background and have been using programs like PhotoShop since the dark ages.
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@Gondola all apologies, I had to… (having been there too when Photoshop was first released…)  |
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