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The Crescent Nebula
Image Details
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How This Image Was Taken

 
The Crescent nebula


Telescope

Astro-Physics 155mm Refractor @ f7
Astro-Physics 1200GTO Mount


Camera
SBIG ST-10XME
SBIG Colour Filter CFW-10


Image Acquisition
MaxIm DL V4.53

Date Taken
5 May - 8 June 2006
70% - 85% Moon phase, mag 3.0, mag 4.0 sky.


Exposure Details

Narrowband = 12 exposures H-alpha 1x1 binned
10 exp OIII, SII 1x1 binned
MaxIm sub-exp ratios 1:1:1

Standard RGB exposures RGB = 7,7,8 x 5 min binned 1x1

All images dithered - to improve signal/noise ratio.
CCD Temp @ -25°C


Image Processing
Raw Lum Ha, OIII, SIII, Dark, Bias, Flat and Flat Dark frames acquired, reduced & combined in MaxIm.
Ha images Sigma clip aligned, combined, de-bloomed and stretched in Maxim. Ha used as luminance channel.

Narrowband colour channel mix: R=Ha,G=SII, B=OIII.
RGB used to create star colour layer and merged with narrowband image.

 

 



Click for full size image


Also Known As

NGC 6888
Caldwell C27
SH2-105

Constellation
Cygnus

Position RA and Dec
In this image North is Up. The image centre is at GSC:4774:810
Image centre is at approx
RA: 20h 12m 20s
DEC: 38d 22m 39s


Highest Altitude at This Site
Approx 75°
This field is centred on star SAO 69592


Distance

About 4,700 light years.

Size & Magnitude
Approx 20 x 10 arcminutes
Mag 10 approx


What it is
The Crescent Nebula is a rapidly expanding shell of gas surrounding a dying star. The Crescent Nebula began to form about 250,000 years ago as central Wolf-Rayet star WR 136 began to shed its outer envelope in a strong stellar wind, expelling the equivalent of our Sun's mass every 10,000 years. This wind has been impacting surrounding interstellar gas, compacting it into a series of complex shells, and lighting it up.