NGC7635 Bubble Nebula

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2012/07/25 - Used 20 minutes subframes with this object, nights are getting a bit longer. Spend 2 nights on this Bubble. Seeing was ok, but could be better.

NGC 7635, also called the Bubble Nebula, Sharpless 162, or Caldwell 11, is a H II region emission nebula in the constellation Cassiopeia. It lies close to the direction of the open cluster Messier 52. The "bubble" is created by the stellar wind from a massive hot, 8.7 magnitude young central star, the 15 ± 5 M☉SAO 20575 (BD+60 2522). The nebula is near a giant molecular cloud which contains the expansion of the bubble nebula while itself being excited by the hot central star, causing it to glow. It was discovered in 1787 by William Herschel. The star SAO 20575 or BD+602522 is thought to have a mass of 10-40 Solar masses.

With an 8 or 10-inch (250 mm) telescope, the nebula is visible as an extremely faint and large shell around the star. The nearby 7th magnitude star on the west hinders observation, but one can view the nebula using averted vision. Using a 16 to 18-inch (460 mm) scope, one can see that the faint nebula is irregular, being elongated in the north south direction.

Object information
Name : NGC7635 Bubble Nebula
Type : Nebula
Constellation : Cassiopeia
Distance : 11K light-year
Apparent dimensions : 15' x 8'
Apparent magnitude : 10.00

Image information
Image date : 2012/07/25, 2012/07/24
Right ascension : 23:20:48.300
Declination : 61°12' 6.00"
Focal length : 0.00 mm
Focal ratio : 
Image resolution : 0.000 arcsec/pixel
Field of view : 
Guiding rms : 0.29 x 2 = 0.58 x guiding imagescale 1.3 arcsec/pixel = 0.75 arcsec
Sensor temperature : 0°C
Light frames : 11 hours, 40 minutes total exposure time
12x 1200 sec. hydrogen-alpha unbinned
12x 1200 sec. oxygen-III unbinned
11x 1200 sec. sulfur-II unbinned
Image acquisition scripted with Nebulosity v3
Auto-guiding with PHD (medium dither, settle < 0.4)
Bias frames : 100x unbinned
Dark frames : Bap pixel map
Flat frames : 6x hydrogen-alpha unbinned
6x oxygen-III unbinned
6x sulfur-II unbinned
Created with Gerd Neumann Aurora flatfield panel
Processing : PixInsight for calibration (bias frames, bad pixel map and flat frames), alignment and integration.
Adobe Photoshop CS6 for final touch.

Equipment information
Telescope : Sky-Watcher BKP250 10" 1200mm f/4.8 Newtonian
Corrector : Guan Sheng Optical 2" coma corrector and field flattener
Focuser : Moonlite CR newtonian focuser with DC motor and USBnFocus adapter
Mount : Sky-Watcher NEQ6-Pro german equatorial mount controlled with EQMOD via HiTec Astro EQDir
Camera : QSI 683wsg-8 cooled CCD camera with Kodak KAF-8300 sensor and Off Axis Guide (OAG) port
Guidecamera : Starlight Xpress Lodestar autoguider
Filters : Astrodon Tru-Balance E-Series LRGB & Astrodon 3nm H-α, 3nm O-III, 3nm S-II and 3nm N-II
Observatory site : Etten-Leur, The Netherlands