Archived posting to the Leica Users Group, 2007/01/19
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]At 08:30 PM 1/19/2007, G Hopkinson wrote: >Very interesting Marc. I am by no means expert. I was familiar with >the method of calculating the exit pupil diameter and the >twilight factor performance as espoused by Zeiss. Please immediately >mail to me any Zeiss binoculars that you may have on hand with >large objectives as they are of no use to you ;-) >Seriously, I've now dug out some Zeiss binocular literature here and >with the equation calculation, it also suggests that "the >twilight performance factor only serves as a reference and does not >give an indication of the twilight efficiency of a binocular. >This is determined by high transmission in the correct spectral range, >a low stray light component, high contrast and resolution" >Hey, this starting to sound like why we like and appreciate good >German glass around here. > >I was pleased to hear that you found your K&E Log Log Duplex >Decitrig hiding under some Ciro-Flex literature :-) ;-) You were pleased? I was DAMNED happy to find it. A day without a slide rule is a day wasted in my life, and I've not been able to find it for a month, though I have been using my King cylindrical in the meantime. I do note that the cursor clasp has been broken and I hope K&E is still about so that I can get a replacement without having to buy an entire slide rule for one silly and non-essential part. None of these mathematical calculations amount to much, Hoppy. USE binoculars. That is the only way to learn. I cannot tell you how this aged 56-year-old-man can use a pair of 15x,60mm glasses handheld on the stars, but I can do so: come here and I shall struggle to teach you. Otherwise, learn as I did, by years of doing so. (That isn't meant to be nasty: it is just that I have learned things by doing them. The first time I tried to load an LTM camera I was stymied. Then I tried a couple of times on bogus rolls of film and it didn't work. THEN I read the instructions neatly printed on the inner bottom of the camera, took out my Swiss Army Knife, and all was perfect, and never a problem since then on an LTM camera. Yes, Kodak went from a long-leader in 1975, the last major producer to do so. The others had gone to a short-leader format decades before. I do have a roll of Soviet film from the early 1990's which has a long leader, somewhere in a box buried away somewhere ... ) A pair of 8x40 glasses should work well for most birdwatching purposes, and 10x40 for stargazing. For the teen-agers in the group, a pair of Docter Optic 15x, 60mm glasses will be ideal but, for me, I enjoy the power but lose the vibrance of the image due to the age deterioration of my eyes. (My hearing is exceptional, though I generally refuse to listen to things I do not want to hear. My vision has always been only normal, and it is rather odd that I have become such a student of optics.) Thank God I found my slide rule. That King cylindrical thing confuses me, albeit it gives four-figure accuracy. Marc msmall@aya.yale.edu Cha robh b?s fir gun ghr?s fir!