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