Centaurus L.A.
Posted: Mon Apr 11, 2022 4:32 am
We had a few really clear good seeing nights last week, but instead of doing something normal I squandered them by chasing after a unicorn! From the wrong side of the planet, no less. 
I did this last year with my refractor to get about an hour on Omega Centauri skimming the horizon, fully extending my mount and then drift aligning it in PHD2, as I cannot see Polaris from my low southern window.
This year I used NINA TPPA to polar align, which was far easier than drifting it. But I was very apprehensive lifting, aligning, and balancing my Newt (with D5300 and guide scope attached) way up high like that!
The pixel scale of 1.3" probably also wasn't the best for this, but I figured I really needed the F/4 for what I knew would be a one-night stand only.
I managed to acquire a little more than 2 hours of data, but threw out the worst stuff to keep only 1.75 hours. No guiding - I tried but it just didn't work. Probably a rookie mistake with my new guide cam. Stars are quite faint there to begin with, even putting aside the extinction, so I should have altered the gain. But subs were only 20 seconds, so I just let the HEQ5 track along on its own.
Amazingly, something showed up, though it wasn't pretty. Probably from various tree limbs and leaves floating through the imaging, and the random neighbor turning on a porch light.
Ultimately this required some techniques I typically don't employ, such as separating out the processing and layering them back together. But, despereate times! Stacking was in ASTAP with lights, flats, and bias. After seeing how much atmospheric dispersion I had (a lot), I ran that stack through DSS' RGB align. I then made one image that was optimized for the stars, then another for the galaxy. I did, however, make sure that the galaxy processing still separated out the target, suppressed nearby noise and gradient, and lowered the shadow dynamic range, so that the mask for the final layer blend (selected based on brightness) would not accidentally turn noise or a higher background level into fake detail.
What I got was still a pittance of the actual galaxy itself, which of course is like 4x bigger than this, but I was pretty happy to get enough to start to show some of those S-shaped dust lanes. And the stars turned out pretty nice too, especially after the RGB align. Used ST to sample and set the balance, and they seem to match up well with the colors in "real" images of this.
Anyway, one of those "just to say I did it" from greater Los Angeles sorts of things. I know that quite good ones have been taken further south like from San Diego dark sites, and with better equipment, but for my backyard - I'm probably good with it.
I did this last year with my refractor to get about an hour on Omega Centauri skimming the horizon, fully extending my mount and then drift aligning it in PHD2, as I cannot see Polaris from my low southern window.
This year I used NINA TPPA to polar align, which was far easier than drifting it. But I was very apprehensive lifting, aligning, and balancing my Newt (with D5300 and guide scope attached) way up high like that!
The pixel scale of 1.3" probably also wasn't the best for this, but I figured I really needed the F/4 for what I knew would be a one-night stand only.
I managed to acquire a little more than 2 hours of data, but threw out the worst stuff to keep only 1.75 hours. No guiding - I tried but it just didn't work. Probably a rookie mistake with my new guide cam. Stars are quite faint there to begin with, even putting aside the extinction, so I should have altered the gain. But subs were only 20 seconds, so I just let the HEQ5 track along on its own.
Amazingly, something showed up, though it wasn't pretty. Probably from various tree limbs and leaves floating through the imaging, and the random neighbor turning on a porch light.
Ultimately this required some techniques I typically don't employ, such as separating out the processing and layering them back together. But, despereate times! Stacking was in ASTAP with lights, flats, and bias. After seeing how much atmospheric dispersion I had (a lot), I ran that stack through DSS' RGB align. I then made one image that was optimized for the stars, then another for the galaxy. I did, however, make sure that the galaxy processing still separated out the target, suppressed nearby noise and gradient, and lowered the shadow dynamic range, so that the mask for the final layer blend (selected based on brightness) would not accidentally turn noise or a higher background level into fake detail.
What I got was still a pittance of the actual galaxy itself, which of course is like 4x bigger than this, but I was pretty happy to get enough to start to show some of those S-shaped dust lanes. And the stars turned out pretty nice too, especially after the RGB align. Used ST to sample and set the balance, and they seem to match up well with the colors in "real" images of this.
Anyway, one of those "just to say I did it" from greater Los Angeles sorts of things. I know that quite good ones have been taken further south like from San Diego dark sites, and with better equipment, but for my backyard - I'm probably good with it.
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- NGC 5128 ASTAP stack RGB Aligned DSS Layers ST8 2D 1200.jpg (498.32 KiB) Viewed 1594 times
