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Old 08-05-2013, 11:31 AM
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PRejto (Peter)
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Join Date: Jan 2011
Location: Sydney, Australia
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First Partial Result With ONAG

http://www.pbase.com/prejto/image/150070295/original
http://www.pbase.com/prejto/image/150070295/large

I decided to post here rather than in the images section because these results are very preliminary and I need a lot more data. Still, this is my first attempt at guiding through the ONAG. Photo is the full 1x1 frame uncropped. Setup is as follows:

TEC140 - ONAG - Hutech IDAS Filter - AP BARADV 2x barlow - G2-8300
- ONAG - ST-i (at f7)

Plate solve indicates resolution of .59 arcsec = F13.5 (1890 mm)

60 min total (12 x 5 min subs) of M83 unbinned.

I used focus max and had FWHM ranging from 2.24 - 2.69. No processing on the image other than some mild deconvolution and DDP in CCDStack.

At first I found setting up the ONAG for guiding rather confusing and I had trouble focusing. While the focusing isn't very exact sliding the tube in and out of the locking mechanism I was able to get better focus by rotating the camera on the threads of the tube and then locking it down with the retaining ring. This works OK if you have enough free cable to twist and if you don't need/want the guide camera oriented a particular way. Unfortunatly the first night I tried to do this the seeing was quite poor and I couldn't seem to lock focus in. A better night made a huge difference not only in focus but with guiding as well. It was just my bad luck to try this out first on a bad night and to not recognize that seeing was the cause of my difficulties! I also had to work out a way to be at the scope without breaking down my whole imaging computer and to set up outside just to focus or move the stage of the ONAG to find a good star. I found a good way using an Ipad with remote desktop installed. I used a free app called LogMeIn and it worked perfectly. I was a little bit worried about latency but I couldn't detect any. Focused stars have a different shape after passing through the mirror of the ONAG. They look like a small cross. The star shape in TheSkyX guiding software also looks a bit different. The plotted star shape (see photo) in the graphs window looks fatter and often has two small peaks. I found I could guide well binning 2x2 with rather long exposures (6 sec +) and aggressiveness set to 4 or lower. The longer exposures seem to even out seeing. In any case I was guiding through the TEC at f7 while capturing at f13.5

I'm hopeful that with a lot more data this might turn into a nice image. I would appreciate any comments. I'm new enough at all of this that I might be missing something obvious.

Thanks,
Peter
Attached Thumbnails
Click for full-size image (Guiding May 6-03-M83.jpg)
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Click for full-size image (ONAG + Barlow & Filter.jpg)
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Last edited by PRejto; 08-05-2013 at 11:45 AM.
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