30.6 ± 4.6 MLy

Continuing galaxy season, I noticed my last attempt at NGC 2903 was 5 years ago and thought I could probably do better. This is a pretty barred spiral galaxy with a lot of dynamic range. I had a bad dust donut in the L data that didn’t get removed by flats (guess I need some new flats!) so I spent a lot of effort removing it. RGB alone was actually pretty pleasing but I think the image was still better after adding in L. I found that StarTools’ new “wipe” module has a large effect on the RGB color, and over the couple of weeks I have been messing with the processing I have vacillated back and forth about whether or not I like it. I even compared with a nice set of images from Astrobin to get an idea of what others have taken to be the “correct” colors. That still did not decide it for me for sure, though I lean toward the “unwiped” version. So I finally decided I would post both versions and would love to hear opinions. This first one is “unwiped.” In the end the only thing I’m sure of is that both versions are better than my best previous, and that’s what I’m shooting for.

Date: 28 Feb 2020
Subject: NGC 2903
Scope: AT8IN+High Point Scientific Coma Corrector
Filters: ZWO 31 mm diameter unmounted L, R, G, B
Mount: EQ-6 (EQMOD 2.000j)+PEC
Guiding: Orion Thin Off-axis Guider + ASI120MM-mini +PHD 2.6.7 (Win 10 ASCOM)
Camera: ASI1600MM-Cool, -20 °C, Gain 139 Offset 21
Acquisition: Sequence Generator Pro 3.1.0.454
Exposure: 75x180 L, 14x180 R, 25x180 G, 25x180 B
Stacking: Deep Sky Stacker 4.2.3 (64-bit) dark+flat+bias, κ-σ stacking with κ = 1.5.
Processing: StarTools 1.6.387: For L, software binned 2x2, cropped, developed, HDR optimized “reveal all”, deconvoluted, and untrack denoised (grain equalization). Combined R, G, & B in StarTools, accounting for exposure total times in combination. 2x2 software binned, cropped, either wiped or did not wipe at this stage, developed, HDR optimized “reveal all,” color module with some saturation boost. Untrack denoised (grain elimination). In Photoshop, did some layer-masked levels work to clean up the stacked L data, then applied L as luminance layer at 100% opacity. Did a bit of saturation boosting and a bit more layer-masked levels & curves adjustment, deliberately bringing the background above pure black. AstroFrame.