Crescent Nebula
Wolf-Rayet Bubble in Cygnus



NGC6888: This is a nebula formed by the action of the central star (the huge blue star at the center of the nebula) expelling its outer gases as it begins the process of dying. At the first stages of its death throes, the star became a red super-giant, and gently puffed out its outer layers, approximately 250,000 years ago. Then it became a type of star called a Wolf-Rayet, a rare, short-lived super-hot star, which started expelling gas at a very high rate (an amount of mass equal to our sun's entire mass each 10,000 years), and at very high speeds, which caused the expelled gas to assume something of a shell shape. It is thought that the central star will become a supernova in the next million years. The nebula is about 4,700 light years from Earth and is roughly 16 by 25 light years in dimension.


Technical Information:

RRGB: 152:35:35:81 (L-19x8; R&G-7x5; B-9x9). The luminance images, taken though a red-pass filter, were unbinned; the RGB channels were binned 2x2.

Equipment: Meade 10" LX200 at f/6.3, an SBIG ST-8XE camera/CFW8 color filter wheel, guided by an SBIG AO-7 adaptive optics device, guiding at about 6.5 Hz.

Image Acquisition/Camera Control: CCDSoft V5.

Processing: All images calibrated (darks, dawn flats and flat-darks) and registered in CCDSoft V5. All calibrated images debloomed using Ron Wodaski's debloomer. I took 34 Luminance images, and chose the 19 with the lowest FWHM. All layers average combined in CCDSoft. One fast Richardson-Lucy deconvolution, and ten slow (high frequency components only) iterations perAIP4WIN. Color combine, and adjustment of curves and levels, performed in Photoshop 6.0.

Location: All images taken from my yard in Redmond, Washington, USA, elevation 500'.

Date: Luminance images taken on the night of August 19, 2003; RGB taken on the night of August 20, 2003.

CCD Temperature: -20C

Moon Phase: Third quarter

Seeing: Very good; individual images measured approximately 3 arcsecond FWHM, but that was with a .63 focal reducer. Luminance layer deconvolved to about 1.8 arcsecond FWHM.

Image resolution: 1.167 arcseconds per pixel

Copyright 2003 Mark de Regt