58,000 Ly

This is a first try on M53. It surprises me that I’ve missed this globular for so long. I chose it this time because I wanted a target that would tolerate more moonlight. I had some difficulty getting this image because clouds kept interfering. I got L and R and some G data a few days ago (when the Moon was quite bright) and just managed to squeeze in more G and B last night before the clouds returned and shut me down. The colors on this look a bit too magenta, but I can’t seem to do better without messing things up more than I help. I’ve taken to stretching a bit more than I used to, and leaving in a little bit of sky fog. I can’t always tell whether the fog is real or is a processing artifact, but I think I like the images better when it’s left in, and I’m less likely to delete real things in the background that way. There is mention of possible tidal streams associated with this cluster; could that be what I’m seeing? Wow, at a reported distance of 58,000 Ly (apparently calibrated from the luminosity of variable stars) this is farther away than any other Milky Way globular I have imaged. It must be pretty large to have such a large apparent diameter.

Date: 11, 14 Apr 2020

Subject: M53 (globular cluster in Coma Berenices)

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 3.1.0.457

Exposure: 40x180 L, 15x180 R, 20x180 G, 13x180 B

Stacking: Deep Sky Stacker 4.2.3 (64-bit) dark+flat+bias, κ-σ stacking with κ = 1.5 except median stacking for B.

Processing: StarTools 1.6.392 beta: Software binned L 2x2, cropped, wiped, developed, HDR (reveal core), deconvoluted, untrack denoised (grain equalization). Combined R, G, & B in StarTools, accounting for the differences in integration. Software binned 2x2, cropped, wiped, developed, HDR (reveal all), color, untrack denoised (grain removal). Applied L to color in Photoshop. A little bit of levels, increase star color, one round of deep space noise reduction. AstroFrame.