Quote:
Originally Posted by Ryderscope
Based on the Nyquist sampling theorem, in a ideal world we would design our imaging system to be 1/3 of the target FWHM we would like to be able to image.
So again, my conclusion is that "seeing" conditions as reported using FWHM figures should always cite the image scale for the optical system in use.
Clear skies,
Rodney
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Well we do have some figures from Mike's scope.
https://pbase.com/strongmanmike2002/image/173190465
Camera:
https://www.sxccd.com/product/trius-pro694/CCD
type:
ICX694AL Exview CCD with ultra low dark current and vertical anti-blooming.
CCD Full resolution pixel data: Pixel size: 4.54uM x 4.54uM, Image format: 2750 x 2200 pixels
Online calculator.
http://www.wilmslowastro.com/softwar...m#ARCSEC_PIXEL
CCD arc-sec/pixel & Focal Ratio.
Focal length of scope 1120mm
CCD pixel size (microns) 4.54
Calculated arcsec/pixel
0.84 arcsecond/pixel.
https://www.techtarget.com/whatis/de...yquist-Theorem
Quote:
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The Nyquist theorem is also known as the sampling theorem. It is the principle to accurately reproduce a pure sine wave measurement, or sample, rate, which must be at least twice its frequency.
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So it's not really 1/3 but 1/2.
Therefore I think any measurements Mike makes on his FITS files
will be considered reasonable and able to be trusted -
such as here:
https://pbase.com/strongmanmike2002/image/173195561
1.665 arc seconds seeing.
cheers
Allan