Re: Star Eccentricity Help
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I think you may be thinking of star flatness?
i snagged this description out of PI's subframe selector - btw in this doc they spec 0.42 as being perfectly round
Eccentricity is a measure of star profile distortion. Given an elliptical star profile with major axis diameter a and minor axis diameter b where a is greater than or equal to b, the star profile eccentricity equals (1 - b2 / a2)0.5, the star profile aspect ratio equals b / a and the star profile flatness equals a / b - 1. For all stars fit in an image, their Eccentricity is weighted by the StarResidual value to minimize the influence of bad fits. A distortion with an eccentricity less than about 0.42 is not perceptible to most people. The table below shows the relationship between these measures.
On Sun, Aug 9, 2020 at 12:54 PM Mike Shade <firstname.lastname@example.org> wrote: