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The Crescent Nebula
Image Details
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How This Image Was Taken

The Crescent nebula


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

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


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


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.