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Re: [vsnet-chat 6013] Re: [AAVSO-DIS] Re: v1413 Aql - Ready for Eclipse > The 90 quanta is incident on the eye externally. 10% will get thru to be > detected by the rod cells. A single photon can produce a measurable > cell membrane hyperpolarization, but thats done by using patch-clamping > techniques in vitro on isolated cells. Okay, this well describes what I have learned in the past. > In vivo, it takes 5-9 quanta to produce a measurable retinal response. The condition of this "in vivo" may be different from the conditions going on observer's retina. It may have been that Hasegawa-san's sensitivity to membrane hyperpolarization was higher (are there any measurement of dispersions of such sensitivities?) than the specimen used to deduce the quoted value. > I would say 13.5 at 50% detectability under good dark skies, not in the > city. My experience was in Kyoto light-polluted sky. Magnitude 13.5 was relatively easily achieved. > Its important to use accurate photometry for these determinations, rather > than quicklook reports using old charts and bad comp stars! This is one of illustrative examples. Even before the CCD era, we preferrably used V-magnitude sequences, which are presently proven to be correct at least to the accuracy of measuring the sequences. Well before the AAVSO adopted correct V sequences, we had correct V sequences for many variable stars. The late Prof. Huruhata was pioneering in determining these V magnitudes. > You can try to wait for a rare string of photon hits, but those will be > infrequent. When it happens, the object may appear briefly but then vanish > again for a much longer period. In a realistic star field, it will be very > difficult to positively identify a faint object below your limit if seeing > it just 5% of the time... Observations made like this should be highly > suspect. There was a proposed method, at least among us, to record (or remember) the number of positive photon (packet) detection events at the variable and comparison star within certain time, and regard the difference just as Pogson's step value, or use them for interpolation method. From this description of the proposed method, it may have been possible that observers actually recognized the time fraction of postive detections. If the expected location of the variable is more frequently detected than the background, wouldn't it be reasonable to positively record the detection? (We are naturally, perhaps unknowingly, applying the same technique to CCD photometry). Yes, these "observations" should have been incorrect to a certain statistical limit, but they more exactly decribe what was recognized, rather than completely discarding infrequent detections. Regards, Taichi Kato
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