Contains: M 82, NGC 3034, M 81, Bode's nebulae, NGC 3031
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M81 & M82, Bode's Galaxies, HαLHαRGB, 4 & 11 May 2017

Technical card

Resolution: 4377x3330

Dates: May 4, 2017May 11, 2017

Frames:
ZWO Blue 31 mm: 12x300" -20C bin 1x1
ZWO Green 31 mm: 12x300" -20C bin 1x1
ZWO H-alpha 7nm: 14x600" (gain: 139.00) -20C bin 1x1
ZWO H-alpha 7nm: 4x600" -20C bin 1x1
ZWO Luminance 31 mm: 36x300" -20C bin 1x1
ZWO Red 31 mm: 12x300" -20C bin 1x1

Integration: 9.0 hours

Avg. Moon age: 12.04 days

Avg. Moon phase: 82.12%

Astrometry.net job: 1578444

RA center: 148.924 degrees

DEC center: 69.294 degrees

Pixel scale: 0.860 arcsec/pixel

Orientation: 88.078 degrees

Field radius: 0.657 degrees

Locations: Mapleton Lateral Observatory, Mapleton, Utah, United States

Description

At the risk of posting two very similar images back-to-back, I added some Hα data to this year’s Bode’s Galaxies image. After shooting a few 600-s frames at the “0” (maximum dynamic range) setting, I decided I just wasn’t getting enough signal to a switched to unity gain (the “139” gain setting) and was more satisfied. Processing this was difficult. I used a 50/50 mix of the original R channel with the Hα for R, then mixed in little Hα with L to create a new L. The difficult part came when I attempted to get the color balance right. There was certainly nothing scientific about it. I used a lot of layer masking with color balance tweaking and also worked hard to make sure the “jets” coming out of M82, which are most prominent in Hα, were visible. I was pleased to see some of the Hα emission regions in M81 also showing up. A better image will have to wait until next season.

Date: 4 & 11 May 2017
Subject: M81 & M82, Bode’s Galaxies
Scope: AT8IN + High Point Scientific coma corrector
Filters: ZWO 31 mm diameter unmounted L, R, G, B, Hα
Mount: EQ-6 (EQMOD 2.000j)+PEC
Guiding: Orion Thin Off-axis Guider + DSI +PHD 2.6.3.2 (Win 10 ASCOM) using predictive PEC algorithm
Camera: ASI1600MM-Cool, -20 °C, Gain 0 Offset 10, some with Gain 139 Offset 21
Acquisition: Sequence Generator Pro 2.6.0.21
Exposure: 36x300 L, 12x300 R, 12x300 G, 22x300 B, 20x600 Hα
Stacking: Neb 4.1.5, flats & darks, trans+rot align, Nebulosity 1.5σ stack and align.
Processing: StarTools 1.4.327. Stretched and deconvoluted the luminance. Combined RGB in Neb 4 and stretched, color balanced, and sharpened in StarTools. Layered luminance over RGB in Photoshop CC 2014, boosted the vibrance a lot and saturation a little. Applied GradientXTerminator medium/high. Layered RGB on top of the LRGB as a color burn at ~40%, then masked out the galaxies and gaussian blurred the mask. Mixed 50% R from this with 50% Hα and used that as the final R. Mostly used the original L, but to make the jets of M82 show up I added some Hα to the luminance in the area of M82. Then lots of layer-masked color adjustment to make the Hα show up well without making the galaxies or the background look too nasty. Topped off with AstroFrame

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Author

David Dearden
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M81 & M82, Bode's Galaxies, HαLHαRGB, 4 & 11 May 2017, David Dearden

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ZWO ASI1600MM
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