23 MLy

M51 is one of my favorite targets and a fitting way to start the 2020 galaxy season. I tried to go a bit deeper than before, with the conflicting goals of picking up the tidal streams and avoiding too much noise in the background. I always seem to struggle with colors for this target, and this attempt was no exception. I kept getting way too much green, even though I took fewer green subframes than red or blue. This image involved using the newest beta of StarTools so I also did a lot of experimenting with new processing modules. Eventually I discovered that if I did not do a wipe on the RGB, the colors came out less intense but a lot better balanced in my opinion. There’s less noise reduction in this image than usual because I used the new “grain equalization” process instead of the older “grain removal.” The new process is definitely faster and I think it generally looks better. Finally, at last I’ve fixed a problem of occasional, intermittent dropped usb connections to my camera that has plagued me for a long time. It turns out it was the usb 3 cable that connected the camera to the usb hub. I also replaced the old usb 2 hub with a new usb 3 hub and so far this has been rock solid. At any rate, this is definitely my best M51 so far.

Date: 26 Feb 2020

Subject: M51, Whirlpool Galaxy

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: 92x180 L, 50x120 R, 41x120 G, 50x120 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, wiped, developed, HDR optimized “soft”, deconvoluted, and untrack denoised (grain equalization). Combined R, G, & B in StarTools, accounting for exposure total times in combination. 2x2 software binned, cropped, 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 levels adjustment. AstroFrame.