The following images depict the Crescent Nebula (NGC6888, also SH2-105), which is an emission nebula about 5000 light years away from Earth.  The crescent nebula is ~25 light years across and can be found in the Cygnus constellation.  This particular nebula is formed by the fast-stellar wind from the Wolf-Rayet star (WR136), which is designated as TYC3151-1765-1 in annotated image.  This star is estimated to be around 4.7 million years old and it is nearing the end of its life.  It is expected to explode as a supernova in a few hundred thousand years.  WR136 is around 600,000 times brighter than our Sun, ~21 times more massive, and nearly 10 times hotter.  When WR136 became a red supergiant, it blew off a shell of material (expanding at 80 km/s), creating this nebula.  Wolf-Rayet stars typically have strong stellar winds and are typically much hotter (20,000K to 210,000K) than typical stars.  This image is the Williams Optic 81mm version.

These pictures were shot with the IDAZ Dual Narrowband filter which is great for heavy light pollution areas (like mine), moonlight, and allows light transmission in two main frequency regions:
1.     Hydrogen Alpha (Ha) (red) at 656.3 nm with a bandwidth of 15nm
2.     Oxygen III (Oiii) (blue) at 500.7 nm with a bandwidth of 35nm

These images were processed in the one shot color format (OSC) – As part of my processing, I isolated the different R, G, & B components to create an image to accentuate the Oiii portion (blue/green), and recombined.  Using a narrowband normalization script, the best results were a SHO image (Sulfur II, Hydrogen Alpha, and Oiii).  In this case, the Sulfur II is a blend of the blue/green channels.

The first image, is with my smaller telescope (Williams Optic 81mm aperture), taken in the early fall of 2022 over 5 different nights (August 27, September 27th – 29th, and October 3rd).  There is a total of 152 different 5-minute images that were stacked together to accumulate a total of 12 Hours and 40 minutes of integration time.  The average moonlight was 16% over these 5 nights.  This image gives a broader perspective of the area (and nebulosity behind the crescent nebula), as well as an open cluster in the lower left-hand side (IC4996).  This open cluster of stars is thought to be relatively young (6 to 9 million years), and at a distance of between 2400 to 5400 light years from the earth·       

• Williams Optics setup
• Mount: EQ6R-Pro
• Telescope: Williams Optics 81 mm Zenithstar doublet
• ZWO-ASI224MC color camera for guiding with the Zenithstar guide
• Hotech Corporation 2” Field Flattener
• ZWO ASI2600MC Pro; Camera cooled to -10 deg C, with ZWO Duo-Band Narrowband Light Pollution Reduction Filter
• Bortle-9 – South Los Angeles shot from my backyard
• Integration Time: 12 Hours 40 Minutes; Lights (152 @ 300 seconds); Darks (30 @ 300 seconds); Flats (40) & Bias (30)

The second image is with my 8 inch aperture telescope, Celestron EDGE HD 8”.  The 8” telescope has a magnification capability of 508x, whereas the 81 mm telescope has a magnification of nearly 203x.  In terms of light (collecting photons), the bigger telescope collects 6.3x more light than the smaller one.  This image was only for a single night, Halloween, October 31, 2023, as the moon was nearly full (luckily, I was able to shoot away from the moon), with an illumination of 91.4%.   I was able to collect 46 5-minute images, that when stacked together accumulated a total of 3 Hours and 50 minutes.·       

• Celestron Edge HD 8” Setup
• Mount: EQ6R-Proo   Telescope: Celestron Edge HD 8” with Celestron 0.7 Reducer – Focal Length is 1422mm with F7 aperture
• Guiding: Celestron OAG (Off-Axis Guider) and ZWO 290MM camera
• ZWO ASI2600MC Pro; Camera cooled to -10 deg C, with IDAZ Duo-Band Narrowband Light Pollution Reduction Filter
• Bortle-9 – South Los Angeles shot from my backyard
• Integration Time: 3 Hours 50 Minutes; Lights (46 @ 300 seconds); Darks (20 @ 300 seconds); Flats (30) & Dark Flats (30)

Image processing

• Image Processing: Pixinsight – Using videos from multiple youtube teachers and website.  @Cosgrove’sCosmos (Thank you for your recent feedback), @ViewintoSpace, @EnteringintoSpace, @Lukomatico – Lots of great on-line teachers/examples.
• Multiple Bill Blanshan scripts (Narrowband Normalization, Screen Stars, Star Reduction)
• Incorporated Russell Croman’s amazing products (Blur, Noise, and Star Xterminators) with the updated Blur Xterminator AI version 4.
• Basic workflow
• Linear Flow
• WBPP (WO Image has a 2x drizzle); Cosmetic Correction; Highest quality
• Dynamic Crop for stacking artifacts
• Gradient Correction Tool
• Autocolor Script
• BlurXterminator (correct only)
• SPCC
• BlurXterminator (ran SPF tool for minimum value; sharpen stars 0.25, star halos (0), sharpen nonstellar 0.90)
• NoiseXterminator (.5)
• StarXterminator


• NonLinear Flow
• Unlinked HT stretch (edge HD image), and GHS (WO image)
• Screen Stars Script – Remove stars


• SCNR for green on Star image (50%)
• Narrowband normalization – SHO – accentuated the Oiii and Sulfer II channels to improve red and pull out the blue/green
• Curves transformation with color masks/game script
• LHE and HDR on the Edge HD image; LHE only on WO image
• NoiseXterminator (0.7)
• Add stars back in with Screen Stars Script
• Reduce Stars with Star Reduction Script
• Annotate and save as .jpg