May be I should put it this way: it seems that BK7 requires aspherisation to obtain good correction with FPL53, but then the correction is excellent. How can I...
... So maybe Baker's suggestion of burying the fluorite (or fluorcrown) element in a cemented triplet replacing the negative center element of a Cooke Triplet...
Is there any advantage to using 2 ED elements in a triplet like some of the Takahashi refractors? Is the ED lens ever choosen as a negative element? Don...
... You can mate FPL53 with anything you wish and get different results depending on your final goal. Fast or slow F-ratio, doublet or triplet or even 4...
... Not really. You can accomplish the same thing with one ED and two crowns. The large airspace is what straightens out the sphero-chromatism. However, this...
Thanks for all of the great posts. After thinking it through, it makes more sense for me to hang on the the Schaefer AT-9 with it's 9" gear and massive drive...
Hello Richard,  I'd tried two S-FPL51 glasses combination. S-BAL41 is the only mating glass. Nothing surprise that jmup out of my computer. The 436nm...
... I like it some in the normal triplet configuration, as well. The only disturbing part is that Chengdu seems to have discontinued H-ZK9. It is not in...
... Glasses come and go all the time. Almost all glasses are available only in small sizes, or they are made in small runs. They tend to have terrible internal...
... But Lens manufactures like to emphasize what glasses inside their lens with blue color. As a consumer, however, I was always curious about elements with...
Here is a example that at least works well on paper. Try a triplet made from Fpl51, BSM81 and LAL14. Put the BSM81 element in front and the LAL14 in the rear....
Scott, This is exactly my point. BK7-FPL53 all-spherical doublet has relatively large higher order spherical aberration. All I want to know is how do I know in...
I do not think one can easily tell without running the numbers through a program. There are trends that one can see but it is not as easy as looking at a slope...
... This is why I originally said that a doublet with full color correction from 400 to 700nm is practically limited to about F12. Anything faster will need to...
I have noticed that the mating glass has to have an index of refraction in the right range. As far as partial dispersion goes both LAL59 and KZFN2 should...
... Now you know why Vixen first produced their 102 Fluorite doublet using KzFN2 and Fluorite. At F9 and 102mm, the combination makes for a very good visual...
Rolando I will do that right after I have finished achieving world peace and fixing the mortgage melt down problem. Scott Walker ... From: uncarollo2 To:...
I can see that the glasses with refraction indices close to that of FPL53, like FTL10, NSL36 or TIL6 make small negative 5th order spherical that can be...
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