Christmas Lights

2024/12/25: M33 grazed the treetops which were undershot by Christmas lights. Maybe some artful cropping and selective red suppression will save the day. I took 210, 60-second frames before changing from UV/IR to Dual Band filtration and recomposing NGC 1499. There are really only so many targets from the backyard, at least while checking out the kit (as I always seem to be doing). Tonight, I aimed at Deneb, recalibrated, then slewed without drama to M33 and from there to the California Nebula.

M33. 210x60s, 400mm F2.8, UV/IR cut filter
ASI1600MC, gain 139, -15C, darks calibrated

NGC 1499. 180x60s, 400mm F2.8, Dualband filter
ASI1600MC, gain 300, -15C, darks calibrated.

Let me tell you about those two. M33 was supposed to be the easy one. But I set up too far south on the back lawn and ended up shooting through the tops of pines, through boughs often underlit by Santa Claus's landing lights. Diffraction through pine needles made star images larger than they ought to be, and illumination by the celebratory lights flooded the field with gradients that had to be filtered out. I used a cleaned up and aggressively cropped and stretched starless image of M33 for luminance behind a stack of all available exposures for color and starfield. What you see here took a lot of rescue work, not all of it successful. There's a lot more galaxy to be got. Next time for sure.

I tried for a color image of NGC 1499, and while I was working toward it, I noticed that by using all the channels as luminance and by balancing them individually, I could get a ton of contrast in the bright bits and retain a great deal of the faint stuff, too. That's what I did with a starless image and then layered the stars back in. The black and white version of this photo works so much better than any color one I've yet produced. Sometimes I think If Saint Ansel had taken up astrophotography (Moons over Hernandez and Halfdome notwithstanding), he would have gone nuts for fields of bright and dark nebulosity. Even more rarely, I get all hubristic and think the result might look something like the image above.

2024/12/25. I've spent more time trying to layer color onto that image than I did acquiring it, processing the data, and working up the monochrome image combined. It's been an intriguing hobby within a hobby, but finally... Merry Christmas. Blow this one up:

NGC 1499. 180x60s, 400mm F2.8, Dualband filter
ASI1600MC, gain 300, -15C, darks calibrated.

Tip o'the day: remember that you can treat noise one channel at a time, so if you get aggressive with the sharpening or stretching and really need to clean up the red or the blue or one more or less than the other, that's fine, go right ahead.

That 400mm Nikon lens is a compact six-inch refractor with somewhat more than 44mm image circle. The 1600MM/MC astrocameras use the central 22mm of the available field, so flatting is not urgent, and star images are clean wall to wall (IFF it's obsessively focused). I don't know how well this glass served the Sacramento Bee as a sports lens, but it's a hoot under the stars, and they're not getting it back. The combination of fast optics, a color sensor with decent hydrogen-alpha sensitivity, and multi-bandpass filters makes good results simple, and presumably makes previously impossible results achievable.

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