[macditto (Niall)]

Originally Posted by alpal

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
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

There is no right or wrong answer here. The higher the multiplier the better the sampling and the closer the image reflects what was received down the OTA. A higher multiplier will always give a better result but it is a law of diminishing returns. But I can tell you from the planetary work I have done that 2X is not enough and 3X is closer to the money. And the question of sampling applies to all forms of astro-imaging including deep sky, since it is just the translation of a photon stream to an image.
The following DropBox link to a planetary image shows the difference in resolution on a planetary image with sampling at a 2.2X multiplier compared with 3.3X. The difference is huge.
https://www.dropbox.com/s/rcai6pwhkz...tions.jpg?dl=0
The 2X multiplier developed by Nyquist was for sound which is a one dimensional array. A 2D array such as an image needs 3X or more, so that the fidelity of the resultant image is not discernible from that potentially coming down the OTA.
Cheers, Niall