This is my first HO image, and was an attempt to go deep enough to capture the Soap Bubble planetary nebula. I would not have thought it possible to capture the Soap Bubble with my gear a year ago (and maybe it wasn’t, then). This image is an HO combination using Annie’s Astro Actions, with RGB stars layered on top and a synthetic luminance that was mostly Hα with a little OIII thrown in to enhance the halo around the Crescent. I used some layer-masked “local contrast enhance” to bring up the Soap Bubble a little, but it is there in both the Hα and the OIII. This image turned out dramatically better than I have ever done before on this target, which is a long-time favorite I tend to image every year.

Date: 16-19 Aug 2017

Subject: NGC 6888 (Crescent Nebula). Soap Bubble planetary nebula is also visible.

Scope: AT8IN + High Point Scientific coma corrector

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

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

Guiding: Orion Thin Off-axis Guider + DSI +PHD 2.6.3.7 (Win 10 ASCOM) using predictive PEC algorithm

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

Acquisition: Sequence Generator Pro 2.6.0.24

Exposure: 30x120 R, 30x120 G, 34x120 B, 41x300 Hα, 20x600 Hα, 78x300 OIII

Stacking: Neb 4.1.6, flats & darks, trans+rot align, Nebulosity 1.5σ stack and align.

Processing: StarTools 1.4.328: Aggressively stretched and deconvoluted Hα and OIII. Combined RGB in Neb 4 and stretched, color balanced, and sharpened in StarTools. Created synthetic luminance mostly from Hα with just a little OIII mixed in to avoid losing the OIII halo around the Crescent. HO combined with Annie’s Astro Actions. Separated stars from RGB background with Annie’s Astro Actions, and screen combined them on top of the HO, followed by a 10% soft light RGB star layer. Several rounds of Carboni’s Astronomy Tools Local Contrast Enhance, layer masked to only affect the rim of the bubble and some of the surrounding dark lanes. AstroFrame.