M56, RGB, 17 June 2020 (David Dearden)

M56, RGB, 17 June 2020

32,900 ly

Continuing my string of globulars, I decided to image M56 while waiting for another target to clear the neighbor’s tree. I did straight RGB imaging with no dedicated L, as this has seemed to work reasonably well for bright targets like globular clusters. I’m pleased with how this turned out, especially given that I did not spend a lot of time either acquiring the data or processing it. I like the intense star colors, which came from the default StarTools treatment without any tweaking. As this object is close to the plane of the Milky Way, the star field is rich. According to Wikipedia, this globular has very low metallicity and is therefore regarded to be quite old (13.7 billion years); it is in a retrograde orbit around the Milky Way, so it is thought it was captured from a merger with a dwarf galaxy.

Date: 17 June 2020

Subject: M56

Scope: AT8IN+High Point Scientific Coma Corrector

Filters: ZWO 31 mm diameter unmounted R, G, B

Mount: EQ-6 (EQMOD 2.000j)+PEC

Guiding: Orion Thin Off-axis Guider + ASI120MM-mini +PHD 2.6.8 (Win 10 ASCOM)

Camera: ASI1600MM-Cool, -20 °C, Gain 139 Offset 21

Acquisition: Sequence Generator Pro 3.1.0.479

Exposure: 15x180 R, 15x180 G, 15x180 B

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

Processing: StarTools 1.6.394RC: Composed R, G, & B accounting for total integration times in creating a combined synthetic luminance. Cropped, developed (94%), HDR (reveal core), deconvoluted slightly (2 pixels), ran the color module with default settings, and untrack denoised. In Photoshop, slight levels adjustment to darken the background, plus a couple of rounds of Carboni’s “make stars smaller”. AstroFrame.

ZWO ASI1600MM/QHY163M
Fast Newtonians
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Status	Advanced success
Started	...
Astrometry.net job	3625912
PixInsight job	WKU9D63TV3QVGUSS1IV8JI6RGWIFY3VV
PixInsight queue size	n/a
PixInsight stage	n/a

RA (center)	19h16m20s.88
RA (top/left)	19h19m01s.62
RA (top/right)	19h13m49s.49
RA (bottom/right)	19h13m40s.53
RA (bottom/left)	19h18m50s.53

Dec (center)	+30°11′26″.2
Dec (top/left)	+30°36′02″.3
Dec (top/right)	+30°38′37″.7
Dec (bottom/right)	+29°46′47″.1
Dec (bottom/left)	+29°43′56″.6

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