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 My goal is to get a total of 480 subs in order to compare 2 vs 8 hours of data. If I am reading the internet correctly that should more or less double the S/N. Shot from Bortel 5 in AZ. 127x120s Gain: 100; Drizzle 2x PI Workflow: DBE > SPCC > BXT > NXT > SXT > EZ SS > EZ HDR > Curves > SCNR > recombine stars after manual stretch. |
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Roughly yes. That should double the s/n ratio. And I believe 8 hours from Bortel 5 will give you very good results. if I may suggest you try a small adjustment on the work flow. Can you try applying NXT after stretching and see if you can find better results? |
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Hi Kevin, Firstly, beautiful image - well done. Not sure if this is an LRGB or OSC CMOS image, and if you've already done this, disregard the suggestion to follow. My experience with BX and NX is that they should be applied when the data is in a linear state. If this is an LRGB, I might suggest processing the Luminance separately, starting by applying BX and NX first, after Integration, then proceed with HT, etc. Process the RGB the same - BX and NX in linear fashion, then move on. If this is a OSC CMOS, the same. After Debayering and DBE, apply BX and NX, then move on to HT, SX, etc. Yes, doubling the exposure subs will definitely yield better signal, but lengthening the sub time will help, also - say 180 to 300 seconds, especially since this is an H-alpha-heavy target. Experimentation is a good practice. - - Steve |
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Steve Solon and Terry Chatterton: Hello Sir. I am about 2 months into this and I’m embarrassed to say I have no idea what HT is. Based on one of the many videos I watched I apply BXT right after I do a DBE and SPCC, then I do a NXT before using SXT. After that I stretch the image using EZ soft stretch as a starting point. thanks for the input and tips. |
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Roughly yes. That should double the s/n ratio. And I believe 8 hours from Bortel 5 will give you very good results. |
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| If I may, don’t drizzle OSC data. I made this mistake early on and drizzled everything because I read that you should. Most of us have a high enough resolution and small enough pixels that although you could drizzle, it offers little advantage. It just adds noise and OSC data doesn’t drizzle very well, not like mono data. Save drizzling for when you need to print big or crop way in. |
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Kevin Knight: I believe HT is referring to Histogram Transformation (image stretch) but I could be wrong which method are you recombining stars+starless? |
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Nick Grundy: ~((~starless_1)*(~stars_1)) |
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Kevin Knight: My apologies, Kevin. I thought you were processing with PixInsight. Yes, as Nick mentioned, HT stands for HistogramTransformation. (PixInsight does not use spaces in its process names). - - Steve |
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Hi Kevin, I find the original version better. It only needs some more care with DBE. Color is better, stars are better, and softer in terms of contrast. The Final image (C) is almost bi-color, has too much contrast (clipped blacks in some regions), and saturated stars. From Bortle 5 I would expect less troubles with gradients, unless there are issues with flat fielding which interfered with gradient removal in this nebula-rich region of the sky. Or clouds!  I don't have any specific PI workflow to suggest, other than the general advice that in terms of post-processing, "Less is more". For two months in the hobby your images are great. How did you manage to find cloudless nights in that short amount of time?  |
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Die Launische Diva: Thanks so much for the feedback. I was just telling the wife, that we should tweak the image until we think it’s good, then back it off about 2 steps. I was unhappy with the stars in the first image as all the bright ones seem to have a little nipple in the exact same stop. In between day 1 and 2 I read up on how to use the subframe selector and got rid of 27 percent of the frames from both nights which help a bunch, but the issue is still there, and I think I over compensated for that and toned them down too much. I get a filter wheel on Wednesday that will complete my setup. I plan on gathering data until it arrives, then grab 2 or 3 more nights with my triband filter, and play around with combining everything. I knew all of this would be difficult, but had no idea of how much there is to learn. |
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Here is what I am calling the final version. Thanks to all the feedback. I wanted to make the stars almost an equal part of the image so I pumped them up a bit, and while not "correct" I think it adds a bit of pop.  |
