12.02.2022 Pondering on imaging.

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 Saturday 12th 33F, cloudy start but brightened to sunshine. Gales from the SW will make it bitterly cold in the observatory. It will probably blow the telescopes around too. Which is worse.

 I have been pondering the Baader D-ERF's ability to sharpen the images in the iStar refractor when lunar imaging. A bit of online homework suggests that an infra red filter finds the most stable seeing conditions. The D-ERF may be fulfilling that function.

 Critical sampling raises its ugly head too. The ASI174 camera has 5.86 um pixels. The critical sampling rule suggests that the f-ratio should be 5x the pixel size. F30 is beyond my reach unless I obtain a 3x Barlow. 4.5m focal length instead of the present 3m with a 2x. How often will the seeing conditions live up to that image scale? If I rebuild the 10" f/8 I shall [theoretically] need a 4x Barlow. That's 8 meters focal length! 

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