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Dates & Location

23rd May - 19th June 2018 from the ICAstro site, Alcalali, Spain. Elevation 230 m
Lat 38°:45.4 N, Long 00°:02.1 W
 

Catalogue identification

NGC 6888
The Crescent Nebula


In this image, North is up

Equipment Used

AstroPhysics AP155 mm focal length, F7.1
Paramount ME German equatorial Mount.
Camera - SBIG STT-8300FWG with internal 7 position FW and OAG
TheSkyX Pro telescope control.
SGP used for camera, PHD Guide and Focus control.

Lakeside Focuser S/W on AP rack-and pinion drawtube

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Where it is in space

This field is approx 116 x 88 arcminutes - ie ~ 4 x 3 Moon diameters
NGC 6888 lies approx 2.75 degrees SW of Sadir, the star at the centre of the cruciform asterism that forms the Cygnus contellation

The nebula is approx 440 light years away in our galaxy and spans about 25 light years

Acquisition

Remote session using Splashtop control from Ravenshead, UK
Exposures: L:14  x 10 min + R:G:B 10 x 10 min each for RGB stars master frame only
Narrowband exposures: Ha 18 x 20 min, OIII 23 x 20 min
Synthetic green channel created from Ha and OIII masters
NB Lum master created from Ha + OIII data


All sub-exposures
-20°C. All images binned 1x1.
Automated remote sessions using Sequence Generator Pro (SGP)

 

  What it is

The Crescent Nebula is an emission nebula in the constellation Cygnus, about 5000 light-years away from Earth. It is formed by the fast stellar wind from a Wolf-Rayet star (WR 136) colliding with and energizing the slower moving wind ejected by the star when it became a red giant around 250,000 to 400,000 years ago. The result of the collision is a shell and two shock waves, one moving outward and one moving inward. The inward moving shock wave heats the stellar wind to X-ray-emitting temperatures. The central star is ejecting the equivalent of the mass of the sun every 10,000 years.

A balanced histogram version of this image is shown here

two loud.

Processing Methods

All data reduction with CCDStack. Lum, RGB masters and RGB colour combine prepared in CCDStack
Master NB colour created in PSCS6
Master (Lum+RGB) colour created in PhotoShop CS6.
DDP stretching, colour balancing and finishing
in PS CS6