This is my most recent image and it quickly became one of my favorites. The star color looks pretty good, not too much weirdness happening with the star shapes, the way the stars seem to get smaller as you move toward the center of the image I think does a really good job at sort of drawing the eye in. There’s a number of things I particularly like about it beyond even that, but I wanted to go over how I captured it and how I processed it to give you some ideas on how you could replicate this kind of work.
This image was taken with a Celestron AVX mount, an Astro-Tech AT72ED telescope, a ZWO ASI1600mm-Cool monochrome cooled camera, 31mm Ha and OIII filters and an Orion 50mm mini guide scope with a ZWO ASI120mm as a guide camera.
I used NINA to capture each frame and plate solve as well as PHD2 for guiding with multi star guiding turned on.
This was also taken in only one night, which I rarely get to do these days because of the need to change filters midway through my shoot. Usually I just capture one filter for each clear night and put them together when I’m ready, but this was a particularly clear night and I didn’t want to lose the conditions.
I took 45, 3 minute images per filter to capture this for a short total capture of about 4 and a half hours. I also captured flat frames that day and used my dark library on top of dithering every third frame.
A big tip I can give you for when you’re deciding what to capture on any given night, check to see what is going to be highest in the sky for the longest amount of time. The closer you shoot to the horizon, the more atmosphere you’re shooting through so you’ll get generally less detail and contrast. The Veil happened to be up right near zenith for a good portion of my time capture it which made a huge difference.
All my data was stacked in deep sky stacker, using the recommended settings, 2x drizzle and intersection mode for stacking. I prefer intersection mode because it tends to cut off the areas where you’re frames didn’t line up giving you a better point to start your editing from. Keep in mind also if you don’t dither drizzle will not work so make sure that’s turned on when you capture.
My processing was done mostly in Pixinsight, but I always do the finishing touches in Photoshop. I started by loading in my two stacked images, one for each filter and renamed them for convenience. I always start off with the backgrounds so I ran both dynamic background extractor and automatic background extractor on them until I saw the background mostly flat.
After that was done I turned to my noise processing technique that I got from Jon Rista, I previously wrote a post up about that so head over and check that out if you’re interested, it provides the best results I have ever seen for astrophotography.
I then made them each non linear with a pretty simple stretch and opened up the star alignment tool. I always align to the Ha frame so I inputted that and ran it. After that gave me my two aligned frames I deleted the original stacked images to clean things up and opened both of my new images.
Here you can open dynamic crop and start with the one with more black space. You’ll want to crop both to the same image so what you want to do is crop to where you want but do not apply the crop yet. Drag the triangle in the bottom left over to your other image to apply the crop there first. Then hit the square to complete it on the first one. That should give you two identically sized and aligned images.
The final thing you’ll want to do is combine them using Pixel Math for a Bicolor image. This is more for you to play around with, but there’s a great guide form light vortex astronomy on combining for bicolor images. Honestly, the guide is so well done that I don’t really have anything to add so take a look at that to find your preferred bicolor combination formula. I’ve linked the page below.
You should now have a combined image that looks pretty good. You might still want to adjust your curves with Curves transformation or adjust your black point with the histogram, but you should be just about finished with your image. This is how I did my Veil Nebula picture above and it’s how I do pretty much all of my bicolor images, although sometimes I will use some other tools like color mask if I feel it’s necessary.