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.
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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.
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