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SEMI-APO ?

Started by rachnoman, 06/23/2015 05:01PM
Posted 06/23/2015 05:01PM | Edited 06/23/2015 05:05PM Opening Post
Does semi-apo mean the same as semi-pregnant?
Posted 06/23/2015 06:15PM #1
Kinda, sorta, maybe, could be. grin

Mike Traub; South Texas; SV80ED : 80mm homemade refractor(Carton lens) :Tasco 10K 80X1200mm:SV80DLtongueST:Vixen GP mount.
Posted 06/23/2015 07:40PM #2
Hi David et al, Interesting that I was just musing over the exact same question then saw your post here. I was looking at the APM bino ads and noting that the trusty 100mm/45-deg Semi-Apo go for ~$1000 and include a nice hard-case and eyeps, the same Apo are ~$2500 and the 90-deg Apo are ~$3000. Far as I can tell the lenses are doublets but I believe the Apos use a more prescious glass to achieve a flat spot in the correction curve = much better color correction. The mechanical build is equivalently better. Stated mag capability for the Semi-Apo is 50X; Apo 100X+. Extreme limit would be a couple of $5000 refractors gone bino (which indeed are available elsewhere as custom-build). As with most things...you get what you pay for. I worked at Bausch & Lomb years ago (when they made world-class premium binos). So I went to the Company Store and tried all their same-sized binos side-by side. The cheapest ones were noticeably deficient but honest good for the (cheap) price. The mid-priced and premiums were nearly identical wonderful in perceived performance; and I'm VERY picky when evaluating optics because that was my job! I concluded that mid-priced binos are the best buy for picky customers. As far as the nomenclature of Achromatic, Semi-Apo, Apo and Premium Apo ... the nomenclature seems fairly ill-defined. Heck, I have a very nice TV Genesis that is without doubt true premium APO - but I STILL see a touch of (completely tolerable) color! The ONLY scopes that I judge as totally color-free are reflectors (of course) and the very $$$ Zeiss hand-helds, like the 20x60 IS that VERY expensive ... and worth it! So, with some irony...I would go more by honest price rather than wording. Ummm...I also have 100mm Obies, astoundingly inexpensive for 100mm binos, fork, tripod, case, eyeps---but (no surprise) find the color and resolution pretty disappointing! Pay more---get more? Tom Dey

29-inch Dob in a dome
36-inch upgrade soon
LUNT 80/80 solar scope
FLI 6803 cam
APM 100mm APO Binos
JMI RB-16 Night Vision Binos
Zeiss 20x60 IS binos
Posted 06/23/2015 07:56PM #3
Oh, I just thought of something else that pertains: The human eye has about 0.65 diopter of undercorrected chromatic, standardized in a red-green test environment target. I measured my red-blue at 0.8 D which is consistent. People's eyes all have nearly the same chromatic because it is the nature of our eyes. We also have spherical aberration. When I got the lenses in my eyes replaced with plastic ones---they are corrected for spherical and my vision is now 20/13 each eye (20/10 when using both). The theoretical res limit of the retina is around 20/7.5 which is like reading fine newspaper print from clear across the room! What I'm saying is that our eyes ultimately begin to trump even the BEST scopes. So judgment of perfection ultimately is more scrutiny of one's own EYES rather than the instrument. This is especially pertinent when judging Astigmatism. I'd better shut up now - I'm an obsessive-compulsive optics guy. DISCLAIMER: My comments are intended for novelty purposes only.

29-inch Dob in a dome
36-inch upgrade soon
LUNT 80/80 solar scope
FLI 6803 cam
APM 100mm APO Binos
JMI RB-16 Night Vision Binos
Zeiss 20x60 IS binos
Posted 06/25/2015 04:05PM #4
I prefer the term "semi-achromatic"
Posted 07/09/2015 08:27PM #5
Gee and here I thought it was a type of truck. :S

"Don't sweat the petty things and don't pet the sweaty things" 8O