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I've been sharing the results of my first astrophotography session and have gotten some initial feedback about needing channel alignment. I found some general info on a PixInsight forum about the process but would appreciate any experience this forum could provide on this topic or others. Thanks everyone. Here's the link to my astrobin post as well as the image copied here for convenience.  |
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Hi Nathan, Firstly, are you shooting mono through filters, or one-shot-color? |
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| Its mono with Ha, S2, and O3 filters |
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| If you haven’t already, assign the Ha to the red channel, OIII to green, and S2 to blue, then combine and adjust saturation levels as needed. If you’ve done the above already, I’ll keep thinking! BTW - is it alignment you need help with, or combining? |
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| Thanks Steve, I think I have the images aligned but I'll review the logs and make sure there weren't too many warnings or errors. I'll take a look at saturation levels as well. I've read a lot of tutorials but am still so new that I really don't know what I'm doing during, especially with processing. I appreciate the feedback though, will keep at it. |
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I'm not a Pixinsight user, so I'm afraid I can't speak to the process there. However, I also don't see an obvious alignment issue. If there were such an issue, I'd expect to see doubled stars, star halos, etc. The clear separations in your image between the different emission regions may look like misalignment but is actually a real feature of the Orion Nebula. You'll see the same thing in most other photos of the nebula , including this one I took over the weekend (with much much less integration time than yours): Yours is larger, has far more detail, and uses a different color palette, but both images seem to show the same basic features, including the clearly delineated emission regions. The only thing that strikes me is the (to my eye) unusual mapping of your narrowband frequencies to colors in the visual spectrum. For that, I'd second @Steve Solon and Terry Chatterton's advice--but unfortunately I don't know how to recommend you do it in Pixinsight. (I could tell you how to do it in AstroPixelProcessor...but that doesn't seem like it would do you any good.) |
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| Thanks Paul, I wonder if I mapped the SHO pallette incorrectly. I think I might just re-process everything after the pre-processing and see what I end up with. I'll post the results. |
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Perhaps. And just a shot in the dark: when you integrated, did you map anything to luminance, or did you only have the individual SHO color mappings? If not, I'd consider mapping the Ha to luminance as well as whatever separate color channel you wind up mapping it to. That might give you brighter stars and less saturated individual color channels. (Hopefully what I'm saying makes some sense in the Pixinsight workflow. Perhaps someone who knows the software can translate/correct me if needed.) |
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Wait, no one sees the alignment issue? Really? Look at the mirroring guys....  This mirroring becomes even more obvious if we look at only the red channel. Looks no Orion I've ever seen before.  Your images are not properly aligned. Run the staralignment process as outlined below. It will fix your issue right up.  Connor |
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Good call! @Connor Matherne, you are so right it hurts. I was looking for a much finer misalignment and missed this big one. Comparing to other images of the nebula, some of the red-channel nebulosity currently at 6:00 in the image (right at the bottom, in the middle) also looks like it should be at closer to 2:00, which seems consistent with your point. And if you look at some of the red stars on the left you will tend to find their yellow 'twins' about 180 degrees away. Looks like maybe Ha is rotated 180 degrees (or so) relative to the other channels. (Or vice versa, of course.) Forget everything else I've posted to this thread.  |
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| Oh wow, I see it now. Thank you so much everyone and! I'll re-run through all the processing and post back. |
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Ran the star alignment and kept most of the other processes the same, looks much less "Thor Ragnarok" and more like some of the other Hubble Palette images I've seen. Going to tinker with it more but here is what it's looking like right now. Thanks so much Connor, Paul, and Steve! |
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| Tip: Even if you think the alignment is good take a minute or two to Blink all of the registered subs together. |
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| On the right track now, Nathan! Your Trapezium looks terrific - keep going! |
