Posted by
SCO on
Nov 11, 2021; 10:17am
URL: http://astroimagej.170.s1.nabble.com/Pixel-scale-adequate-tp1672p1674.html
Thanks Karen.
I probably should have explained why I asked this.
I am buying a new camera specifically for exoplanet work. Camera option 1 has a pixel size of 15 microns and a full-well size of 150,000 electrons. Camera option 2 has a pixel size of 13.5 microns and a full-well size of 100,000 electrons.
The exoplanet manual I am reading says:
6.2.1. Choice of Binning The FWHM of stars in the target field should be spread out over 3-5 pixels. If the imaging camera is normally setup to bin more than 1x1, binning might have to be reduced to achieve this. This then would result in an acceptable image scale (sometimes called “plate scale” or “pixel scale”). Image scale is expressed in arc-seconds per pixel and is a function of the focal length of the telescope and the size of the CCD photosite. For example, assume that the FWHM is 3.0 arcseconds, and the unbinned image scale of the observer’s imaging system is 0.5 arc-seconds/pixel. This means that, without binning, the FWHM would be spread over 6 pixels and that 2x2 binning would mean that that the FWHM would be spread over 3 pixels, still within the acceptable, albeit the lower, part of the range.
Assume a FWHM is 3.0 arcseconds:
Camera 1 has an unbinned image scale of 0.9 arcseconds/pixel
Camera 2 has an unbinned image scale of 0.8 arcseconds/pixel
FWHM for camera 1 would spread out over 3.33 pixels
FWHM for camera 2 would spread out over 3.75 pixels
Both are technically between 3 and 5 pixels and are therefore acceptable (assuming a FWHM of 3.0 arcseconds), however camera 2 is more inline with the 3-5 pixel recommendation. Therefore camera 2 would seem to be the better choice.
However camera 1 has a full-well capacity of 150,000 electrons vs. camera 2 which has a full-well capacity of 100,000 electrons. Therefore camera 1 would be far less likely to saturate as the airmass changes across the sky. In that way, camera 1 would be the better choice.