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NGC6992/5 the Eastern Veil Nebula, in hydrogen alpha light.

These glowing filaments of interstellar shocked gas are part of a larger spherical supernova remnant known as the Cygnus Loop or the Veil Nebula -- expanding debris from a star which exploded over 5,000 years ago.  The Veil Nebula is some 1,400 light-years away toward the constellation Cygnus.  At that distance, witnesses to the original stellar explosion would have seen a star in the heavens increase in brightness to about -8 magnitude, roughly corresponding to the brightness of the crescent Moon.


Image info

Telescope:  Orion 80ED apochromatic refractor at f/7.5

Focus:  Prime focus

Filter:  Astronomik Hydrogen Alpha 13nm FWHM

Mount:  Vixen GPD with Skysensor2000

Camera:  Modified Canon EOS 300D, at ISO800

Guiding:  700mm refractor guidescope, SAC7 camera, autoguided with Guidedog software

Exposure:  Total 86 mins (43 x 120s)

Date:  30th July 2005

Processing:  RAW file conversion, Offset and Dark subtraction, flat fielding, registering and stacking done in IRIS.  Only the Red channel was used.  IRIS pre-processing almost all automated with AutoIt scripts. Curve stretching in Photoshop CS.  Background gradient removal in IRIS. Noise reduction in Neat Image.


Acquisition was managed by GADFly, an AutoIt script I wrote to automatically nudge the position of the guidestar every few exposures.  This is done to avoid noise pattern build-up in the sky background.  In this case, some pattern did appear in the background - probably did not move the guidestar enough during the exposures.


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