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Image sampling confusion

Started by ddoctor, 03/22/2008 05:48AM
Posted 03/22/2008 05:48AM Opening Post
Hi group,
Is there a consensus regarding optimal image sampling for planets? I've seen generalities made such as: f/35-40 or whatever is best, but if I make the same calculation I do for deep sky ccd i.e. 205*pixel size/f.l., which for my 10 f/7 newt is around 5000+mm with a 3x barlow and 8000+mm with a 5x, my final arc sec/ pixel (using skynyx 2-0) is 0.2-0.3!! I seriously doubt I would EVER have seeing good enough for that here in the Northeast. Perhaps I should move? smile
Thanks,
Dave
Posted 03/22/2008 07:39AM #1
David Doctor said:

Hi group,
Is there a consensus regarding optimal image sampling for planets? I've seen generalities made such as: f/35-40 or whatever is best, but if I make the same calculation I do for deep sky ccd i.e. 205*pixel size/f.l., which for my 10 f/7 newt is around 5000+mm with a 3x barlow and 8000+mm with a 5x, my final arc sec/ pixel (using skynyx 2-0) is 0.2-0.3!! I seriously doubt I would EVER have seeing good enough for that here in the Northeast. Perhaps I should move? smile
Thanks,
Dave

That wouldn't hurt. wink

However, even if your seeing ain't good, Registax can help. You want small pixels and you want long focal length, for starters, so there is something for Registax to work with. Get the image scale up and the pixel size down. Oversampling be damned.

Then you want many frames. Almost anywhere, seeing settles down at least occasionally, so take plenty of frames so you can catch these good periods. Take long sequences if your seeing ain't good. 1000 frames is where you START.

The only place where that becomes a problem is Jupiter. It rotates so fast that you need to limit your .avi sequences to about 90 seconds. If the seeing ain't what it oughta be, that means a camera capable of delivering a high frame rate, not a webcam. Yes, you can kick up a webcam's frame rate, but at above 5fps they introduce compression to the images, which will not help.

8)

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