ARO11 / Campbell's hydrogen star
Another image from the unbelievable spell of good weather in August/September. When I imaged ARO11 I did not know that it was identical to Campbell's hydrogen star, not even sure why I imaged it at all.
I mainly took RGB images because the nebula is so bright that no narrow band is needed even in the city. But in RGB the central star was so large that I only used RGB for the background stars and copied a Ha:OIII:OIII image of the nebula into this starfield.
Taken from Berlin with a 10" Meade ACF at f/8 on an AZ-EQ6 mount, Trius SX694 camera, 20x30s each for RGB and 15x30s each for Ha and OIII.
I have attached the cropped but full size version first.
Most remarkable was that the ring structure is moving outward if I make the image brighter. Usually I would expect the inner part to burn out and the burned out part to grow when the image is made brighter. Here the bright part of the nebula just moved outward.
The nebula also has a halo (third picture), which was unknown to me, otherwise I would have done more and longer exposures.
Stefan
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