Hemisphere:  Northern  ·  Constellation: Cassiopeia (Cas)  ·  Contains:  Bubble nebula  ·  NGC 7635  ·  NGC7635  ·  Sh2-162
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NGC-7635 in Hubble Palette (Bubble Nebula), 


            Joel Shepherd
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NGC-7635 in Hubble Palette (Bubble Nebula)

Imaging telescopes or lenses: Skywatcher Esprit 80ED APO Triplet

Imaging cameras: Atik 460EX Mono

Mounts: Advanced VX

Guiding telescopes or lenses: Orion Deluxe Mini 50mm Guide Scope with Helical Focuser

Guiding cameras: Orion StarShoot AutoGuider Pro Mono

Software: PixInsight 1.8  ·  Craig Stark Nebulosity 3

Filters: Astrodon 5nm SII  ·  Astrodon 5nm H-alpha  ·  Astrodon 5nm Olll

Dates:Sept. 12, 2016Sept. 13, 2016Sept. 21, 2016

Astrodon 5nm H-alpha: 15x600" 0C bin 1x1
Astrodon 5nm Olll: 15x600" 0C bin 1x1
Astrodon 5nm SII: 15x600" 0C bin 1x1

Integration: 7.5 hours

Avg. Moon age: 13.84 days

Avg. Moon phase: 78.70%

Bortle Dark-Sky Scale: 6.00

Astrometry.net job: 1287773

RA center: 23h 20' 59"

DEC center: +61° 8' 24"

Pixel scale: 1.748 arcsec/pixel

Orientation: -117.681 degrees

Field radius: 0.432 degrees

Resolution: 1280x1236

Locations: Home, Seattle, WA, United States


Subject: NGC-7635 (Bubble Nebula), near Cassiopeia. The "bubble" is created by stellar wind from a massive hot, 8.7 magnitude central star. The nebula is near a giant molecular cloud which contains the expansion of the "bubble" while itself being excited by the hot central star, causing it to glow. It was discovered in 1787 by William Herschel. [Derived from Wikipedia entry]

Capture notes: The Bubble was a much brighter target than I'd expected: it's almost surprising that it's not more popular. HA and S2 were captured during a period of significant moonlight. I made an attempt to capture O3 on 15 September but was defeated by clouds and ended up discarding everything from that night. O3 from the night of the 21st was much better in every respect.

Processing: I made three complete passes at processing this. It took two passes to get reasonably good quality tone maps; then it became evident that the background processing (flats and DBE) hadn't gone well. On the third attempt, I also improved the SNR and detail in the luminance by stacking all 45 lights together, rather than stacking the individually stacked channels. Narrowband color is still very challenging to me and is something that I'll continue to work on with this target.



  • NGC-7635 in Hubble Palette (Bubble Nebula), 


            Joel Shepherd
  • Final
    NGC-7635 in Hubble Palette (Bubble Nebula), 


            Joel Shepherd

Sky plot

Sky plot


NGC-7635 in Hubble Palette (Bubble Nebula), 


            Joel Shepherd