Celestial hemisphere:  Southern  ·  Constellation: Ophiuchus (Oph)  ·  Contains:  5 rho Oph  ·  B42  ·  IC 4604  ·  The star ρOph  ·  rho Oph nebula
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IC4604, Rho Ophiuchi, LRGB, 12-15 June 2018, David Dearden
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IC4604, Rho Ophiuchi, LRGB, 12-15 June 2018

Getting plate-solving status, please wait...
IC4604, Rho Ophiuchi, LRGB, 12-15 June 2018, David Dearden
Powered byPixInsight

IC4604, Rho Ophiuchi, LRGB, 12-15 June 2018

Equipment

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Acquisition details

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Description

Not realizing how dim the reflection nebula here is, I decided to give Rho Ophiuchi a shot before the Moon got too bright even though this really should be done with a wider field of view than my AT8IN+DSI1600MM-C affords. As the subframes came in, it looked like all I was going to get was a star field, but the nebulosity shows up both in B and in L after stretching. I stretched the luminosity very aggressively and skipped my usual StarTools’ “wipe” step for gradient removal, relying on a new set of flats instead because much “wiping” would have wiped out the nebulosity. Hence, there could be more gradient in this image than there should be. All things considered, this is much better than my last try and turned out better than I was expecting.

Date: 12-15 Jun 2018

Subject: IC4604, Rho Ophiuchi

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 + DSI Ic +PHD 2.6.5 (Win 10 ASCOM)

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

Acquisition: Sequence Generator Pro 3.0.2.82

Exposure: 42x300 L, 20x180 R, 24x180 G, & 20x180 B

Stacking: Deep Sky Stacker 4.1.1 (64-bit) dark+flat+bias, κ-σ stacking with κ = 1.5.

Processing: StarTools 1.4.332: Combined R, G, and B in StarTools. Binned 2x2, cropped, wiped, developed, HDR. Color module, but increased the red bias reduction to roughly match the G and B. No deconvolution. Stopped tracking to smooth. Binned L 2x2, cropped, no wipe, and developed aggressively (~80%, whereas “home in” was headed for a lower value, around 75%), followed by HDR. Masked out the “fat” stars and used moderate deconvolution followed by untrack smoothing. Combined L with RGB in Photoshop. Use Carboni’s Astronomy Tools’ increase local contrast and a couple of rounds of deep space noise reduction. Adjusted vibrance and saturation up a bit. AstroFrame.

Comments

Sky plot

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Histogram

IC4604, Rho Ophiuchi, LRGB, 12-15 June 2018, David Dearden