Exit Pupil Constraints (1 Viewer)

opisska said:

An 88 mm scope is diffraction limited at 1.3 arcseconds. at 50x magnification that's 65 arcseconds. The people who can see deterioration "well before they get to it", that is who see details below an arcminute, are one in aillion prodigies. Maybe on a carefully crafted and perfectly illuminated pattern or something with extreme contrast like sunspots, but on a typical messy texture, human eye is nowhere as good.

If you indeed see this effect at these levels, then either you have literally won the genetic lottery or what limits you is not diffraction, but heat haze, eyepiece quality, residual chromatic aberation of telescope or whatever else is in you way.

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jring said:

remember that the lines from König & Köhler were written at a time when fluorite loaded ED glass was not yet discovered and the only way to get ok colour correction in a fast refractor (faster than f15 or so - nobody in their right mind would have tried todays f5.5 back then) was to use a triplet objective with expensive Sonderglas - which were pretty much reserved to astro telescopes.

See http://www.monocular.info/cz_asiola.htm for what was still a very good spotting scope back then...

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Tringa45 said:

IIRC Zeiss-Jena or maybe even Docter used to produce a scope in 60 mm and 80 mm versions that looked very much like half an Aspectem. It seems though that the new owners, Noblex have discontinued the Aspectem.

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typo said:

Opisska,

My left eye acuity is 66", my right 72", and 62" with both, but these days my vision is on the decline, and I need the aid of a very good optometrist.

It could be genetics. My mothers eyesight was extremely good, and last time I checked, my son's binocular acuity was between 5" and 10" better than mine.

My preferred natural targets for testing are high contrast twigs against the sky at somewhere around 150 to 250m, but I can get pretty close with messy ones if the light is good. My son is better than me on those. My optometrist tells me it's not only my acuity, but my perception that is is rather unusual too, but I know very well there are others that can better me.

David

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