Quote:
Originally Posted by Octane
Ray
On my setup, I dither 4 pixels per frame. This equates to about 14 arcseconds.
H
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thanks for the info H. is that plus and minus or the total? I guess it doesn't really matter - should be plenty anyway.
Quote:
Originally Posted by Amaranthus
Ray, I was using a "High" dither in PHD2 for the above test, which I think is 4 pixels or about 18 arcseconds.
Not sure how to compare the FWHM or HFR across images, because the image scale changes (increases) as one drizzles more. Thus the reported HFR increases from examples 1-5 above. I guess you'd have to rescale it all back to the same resolution to do a fair comparison?
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I guess the most reliable way would be just to scale it all back to arcseconds - then it could be compared with what others get as well.
Thinking about it a bit more though, the dither has to introduce frame to frame offsets that are not just whole numbers of pixels (must include a fraction). That will happen using standard dither if the pixel scale on the guide camera is different from that of the imager. But there might be a relationship that determines how much dither you need for a given ratio of scales. For example if upscaling by 2x, you need data at half pixel offsets to fill in the holes. I think that random offset may do a fair job, but is possibly less efficient than fixed dither - needs more thought. Any ideas?
Also need to ensure that the registration process does not allow distortion of the images - that is probably why Neb's simple registration works so well, but PI is a bit more hit and miss - it's default registration may be a bit too smart - must try dumbing it down.
regards ray