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The Helix Nebula

This is probably the most difficult image I've made yet. At first glance the helix looks easy to image with very good SNR on core rim, but the faint outer shells that I desired were incredibly faint. I started imaging the Helix in early July and continued imaging it over the past 2 or 3 months, however the weather has not played ball and only gave 4 or 5 clear nights. I began imaging with 300s subs but unable to see the faint stuff appreciably at ~10hrs. I then tried adding in 900s subs in the hopes it was shot noise limiting me. Although its possible a combination of LP and moon just hiding the very faint stuff away. This is also my longest integration yet at 18hrs total. I decided to move on since I've sunk too many of the few nights I get into this target and so this is the end result of my processing attempts.

Acquisition Details:

Scope: GSO 8" F/4, flocked, 2" moonlite, DIY AutoFocuser, DIY Secondary Dew Heater Coma Corrector: SkyWatcher Aplanatic/Quattro Camera: ZWO ASI 1600MMC PRO (Image scale ~1"/pixel) Mount: EQ6-R Guide Scope: ZWO 60mm Guide Cam: QHY5LIIC 135x300s Ha 7nm (ZWO) 14x900s Ha 7nm (ZWO) 40x300s Oiii 7nm (ZWO) Roughly 14.75hrs Ha, 3.33 hrs Oiii. Total integration 18 hrs. All at gain 139, 21 offset, -15 degrees celsius. Acquired with the NINA imaging suite. Guided with PHD2. Mount interface: EQMOD

Processing Details:

Pre-Processing: All Lights dark calibrated. SFS/Star Aligned/Image Integration Processing: Crop, DBE, Decon, TGV Denoise, MMT (same for Oiii bar decon) HT Stretch then Linear Fitted both stacks Duplicate Ha for use as Lum. Lum Processing: ranged masked the core and applied LHE, and minor S curves ACDNR with lightness mask RGB Processing: The original stretched Ha and Oiii were then pixel mathed together with the following expressions R=iif(Ha > .15, Ha, (Ha*.8)+(Oiii*.2)) G=iif(Ha > 0.5, 1-(1-Oiii)*(1-(Ha-0.5)), Oiii *(Ha+0.5)) B=iif(Oiii > .1, Oiii, (Ha*.3)+(Oiii*.2)) Many rounds of curves, and ColorMask to shift the cores hue Minor ACDNR on chrominance Final Processing: The LUM and RGB were then combined with LRGB Combination Final Contrast and saturation curves applied
Date Created: 2019-07-07
Date Posted: 2019-10-19