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----- Original Message ----- From: "Michael Linnolt" <linnolt@hawaii.edu> > > Well, I really have doubts about these tests. Personally, I cant seem to > do much better than about 6.8 from Mauna Kea That's because you're at 13K feet on MK. Unless you're using supplemental oxygen, you're going to lose a magnitude or two. Personally, the sky atop MK doesn't look much different to me than a good dark sky at sea level. The O2 shortage will do that. > One of the key factors in naked eye, and it is in > the formula I used to derive it as well, is the aperture of the eye. The > difference between 4.5mm and 7.5mm is 1.1 magnitudes. But there may be > some compensatory effect going on with the older eyes, that is as the > pupil size decreases slowly, the retina develops a lower throshold of > signal detection? Dont know if anyone has studied this in detail. If everyone's eyes could be calibrated to a formula like that we wouldn't be having all these discussions about visual observing! :-> The experience level of the observer is a major factor. The last two summers I've worked with *totally* inexperienced observers. Some of them have difficulty picking out a 10th mag star in an 8" scope - at first. Pretty soon it's easy, second nature, and they can work fainter and fainter. Even an experienced observer has to keep in practice - the best planetary observer I ever knew used to say, "The more you look, the more you see". Still, I do wonder a bit about 16th mag obs with a 4" scope. As someone else says, maybe the comps used were photographic magnitudes, and the stars were brighter visually. 14.5 - 15 I don't think I'd question, using a high-quality refractor under a dark sky. Jim B.
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