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True - but I'd think that if both were less than your image scale, whether one is greater than the other would not matter; you'd get round stars because your pixels would be too large to resolve the difference.
yes i generally agree, but i often see things at or above the image scale.?
also it's the image scale of the imaging setup, not the guide setup. Often the guider is at a more coarse scale, so arcsec is preferred to make that assessment.?
i see a fair number of people saying their guiding is sub-pixel, but it's the much larger image scale of the guiding setup!
On Fri, Dec 11, 2020 at 10:20 AM Arun Hegde <arun.k.hegde@...> wrote:
"Eccentricity (star roundness) really depends on how close RA and DEC RMS are, not necessarily how high is your RMS
?
low RMS = small stars
RA and DEC RMS close in value = round stars"
True - but I'd think that if both were less than your image scale, whether one is greater than the other would not matter; you'd get round stars because your pixels would be too large to resolve the difference. And if both were larger than your image scale and close to each other, you'd have round stars but they'd be larger than they could be from optical effects alone, plus you'd lose feature resolution. So a desirable end point is to have both as well as your total RMS smaller than your image scale.
On Thu, Dec 10, 2020 at 10:42 PM, Brian Valente wrote:
Eccentricity (star roundness) really depends on how close RA and DEC RMS are, not necessarily how high is your RMS
