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M76 Little Dumbell - a dumb choice


MartinB

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Lovely sky tonight, great seeing, no dew but blowing old boots. Not a great time to be imaging at 2500mm F10 esp narrow band but I just wanted to sort out a few gremlins with my active optics unit.

Well the wind got to the image and it was a bit of a struggle but the gremlins are all sorted now (guide cable was dodgy)

This is 10x10 mins each for HA and OIII with a synthetic green channel.

It's a diddy little thing.

9609_normal.jpeg

(click to enlarge)

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Thanks a lot guys. The wind just seems to have the effect of slightly smearing everything. I processed it on my laptop when I got in but have now had a go at it using a decent monitor,

9611_normal.jpeg

(click to enlarge)

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Excellent image Martin, it's a very faint object. I remember a few months ago being extrememly frustrated with a guiding problem, turned out to be a dodgy cable, there's nothing more frustrating. This looks fantastic in narrowband, never seen this object done this way before.

Steve

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Thanks everyone.

Very impressive result. Looks almost as tight as it could be at that FL despite the wind. I don't know what were the problems you had with the AO, I don't have experience of one, but how much difference do you think the AO unit makes?

David I think the AO makes a signifcant difference. Because of the wind I limited the guide exposures to 0.2 secs to keep a good s/n ratio and that was giving 4 guide cycles per second. That was just quick enough to keep the guide star in the window during gusts although I did loose a few subs. I doubt it would have been possible to get many subs guiding conventionally. For the final 20 mins of the session the wind had dropped so I was able to drop the guide exposure to 0.08 secs giving a 10hz cycle. At this speed the stars are really tight with sub 2 arc sec FWHM stars. If you can overcome all the difficulties then AO will improve resolution (provided you can find a bright enough guide star). That's why I've stuck at it.

The problem I was having at Kelling was that the mount wouldn't respond to signals from the AO. Same problem last night so I changed the cable and everything was fine. The AO window only has limited travel so after a while it needs to be recentred by making corrections through the mount.

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Very nice Little Dumbbell Martin - and interesting description on how the AO works.

Sam

Thanks Sam. I feel like saying I now have the AO sorted and working for me but that would be tempting fate. Once I've had a few more successful runs I will do a write up since it is very interesting technology. Nothing like as hard to use as I've made it appear.!

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