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Old 25-03-2011, 10:59 AM
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allan gould
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Eta and bullseye. 40 min sub at 2500mm

I was testing out an off axis guider to see exactly how far I could go with this system and thought that I would post my final picture of this series as it may be of interest to the group.
This is a single frame taken with a QHY8 camera on my 10" Meade SCT at a focal length of 2500mm. The single sub was of 40 min duration and has been stretched in levels and then downsized for posting.
Interestingly this was taken over BrisVegas with its light pollution, so it puts to rest that statement that a cooled CCD needs filters to image from suburbia. The moon was coming up and that was another factor. I can not take more than a 1 min shot with my DSLR under the same conditions.
The QHY8 camera shows almost no noise in this single frame and is a testament to the chip and camera. Just love it.
I doubt that I could have taken such a lengthy sub with a guidescope without the appearance of flexture, especially at a FL of 2500mm. At that FL everything goes pear shaped. The Losmandy mount tracks well and it is a least 10 yr old but has no horror idiosynchrasies.
And Murphys Law operates in deep space as well as on Earth as the plane went smack through the keyhole - good shot by the pilot.
And lastly the stars are almost perfectly round at this FL and guiding time. See the enlargement at 400x.
Comments welcomed.
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Last edited by allan gould; 25-03-2011 at 11:30 AM.
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Old 25-03-2011, 12:00 PM
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RickS (Rick)
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That's pretty amazing, Allan! Both the 40 minute sub and the accuracy of the plane

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Old 25-03-2011, 01:57 PM
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You should talk to hotspur's manager about an APOD for that

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Old 25-03-2011, 03:30 PM
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That's fabulous. Now all you have to do is frame and shoot. So much more fun when the tracking is working well. So not fun when it isn't!

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Old 25-03-2011, 04:20 PM
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Nice shot Allan. Good to hear the guiding is sorted.
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Old 26-03-2011, 12:58 AM
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40min sub huh. niiiice

I wouldn't risk it (planes, satellites, a bump etc..) so you da braver man than I

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Old 26-03-2011, 09:43 AM
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Thanks for all the comments guys. Your right Mike there are too many things that can go wrong in a 40 min sub but I just wanted to see just how far I could push my guiding and still get round stars and at what focal length. I guess it's like with a car, you just like to know what the top speed I'd but you don't do it all the time. At the moment I'm looking at getting the best OAG that I can - any suggestions out there?
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