18th March 2006
Object name: M81 Bode's nebulae
Popular name: Bode's nebulae
Object type: Galaxy
Size: 24.9 11.5
Position angle: 15
Apparent RA: 09 55 33.5 Apparent Dec: +69 04 02
Constellation: Ursa Major
Last time I visited M81 I took five long exposures of 1200s duration. Total 1.66 hours. I have been told lately that there is no point exposing beyond a certain sky background. The sky background in those subs was about 13000 ADU. The suggested max is about 1000-2000ADU. After that length of exposure you might as well gather more shorter frames and stack them So I have tried that with this image. I captured 34 frames at 200s exposure, and discarded 5 of them, giving a total stacked exposure of 1.61 hours. Background brightness about 3000.
It is difficult to draw conclusions at this stage, I really need to reprocess the Jan image along similiar lines, however, the 200s image is not noticably worse - and the stars (ignoring the coma) are better formed.
Do not forget the tiny Holmberg IX galaxy to the left of M81, and the tiny PGC 28505 to the right.
Rather amusingly, whilst sitting in the kitchen (which forms part of the observatory, don't ask!!) the cat jumped in the window with a rabbit in its teeth. Me and the cat spent the next half an hour chasing rabbit around the house until the cat finally had enough and finished it off. Of course, I didn't want to turn the lights on - that would ruin the exposures, so all this larking about was in the dark. What fun.
This image was autoguided using my 400mm focal length refractor and my black and white SC1 webcam.
Captured in Artemis Capture. Calibrated, aligned and combined in Maxim. DDP applied to long L layer. Some filtering in Maxim and tweak curves, resize and save in photshop
Exposure Details :
29x200s on 200mm @ F5 with ART285
Curdridge Observatory, Southampton,UK