1227 LY

What a difference a little more data can make! Not satisfied with the LRGB image I posted a few days ago, I decided to get Hα and OIII data for the Dumbbell Nebula. This target really pops with these filters; I think this is the strongest OIII target I have seen. Processing this image was more difficult than usual and I have struggled with it. Using my normal approach the colors came out very weak and unconvincing. So I tried a lot of different ways of processing and finally settled on separately doing the Hα and OIII. I backed off the temptation to fully stretch to bring out the faint outer portions. This allowed some of the structure of the interior of the nebula to show up without becoming fully saturated. I played with bicolor combination of Hα and OIII, and finally tried layering the LRGB on top as a color layer at 50% opacity, which seemed to preserve the detail and the faint parts of the nebula but gave colors I liked a little better. This also de-emphasized the star field while preserving its color. There’s still more noise than I like, but I’ve spent enough on this now. It’s interesting to see the different shells of gas ejected from the star that show up in this nebula. Now I think I have a better M27 than I got from my OSC camera; it looks like a delicate cosmic butterfly.

Date: 28 June-3 July 2019
Subject: M27, Dumbbell Nebula
Scope: AT8IN+High Point Scientific Coma Corrector
Filters: ZWO 31 mm diameter unmounted 7 nm L, R, G, B, Hα, OIII
Mount: EQ-6 (EQMOD 2.000j)+PEC
Guiding: Orion Thin Off-axis Guider + ASI120MM-mini +PHD 2.6.6 (Win 10 ASCOM)
Camera: ASI1600MM-Cool, -20 °C, Gain 139 Offset 21
Acquisition: Sequence Generator Pro 3.0.3.198
Exposure: 50x180 L, 7x180 R, 15x180 G, 16x180 B, 24x300 Hα, 24x300 OIII
Stacking: Deep Sky Stacker 4.2.0 beta 5 (64-bit) dark+flat+bias, κ-σ stacking with κ = 1.5.
Processing: StarTools 1.4.352: Cropped, wiped, developed (holding back a bit), HDR equalized, deconvoluted, and untrack denoised the Hα and OIII data. Combined using Annie’s Astro Actions HO Bicolor process. Did adjustments to saturation and a bit of curves and levels. GradientXterminator (medium, low). Several rounds of curves+levels. Added LRGB from 29 June 2019 as a color layer at 50% opacity on top of the HO. AstroFrame.