MARK PAJOR said:
guys, wow lots of information there, about different types of glass, went way over my head. So lets say you have a tak fs 102, and a sv 105 next to each other,and viewing though both.Is one better than the other. As far as optical quality.And if not, whats the difference.And do both companies use the same types of glass, or does one use something else, please keep it simply, for all of us beginners thanks
The FS102 is a doublet with the fluorite element in front.
The SV 105 uses a TMB designed triplet.
Doublet - 2 lens elements
Triplet - 3 lens elements
I believe TMB considers their glass types proprietary information, so it'll be hard to track down what glass types they use. When Roland mentions a LZOS lens, he's talking about a TMB designed lens. (LZOS is the Russian company that makes them)
In this case, the fact the doublet has a higher F ratio will help compensate for the difference in color correction between 2 and 3 elements.
Higher F ratios mean more depth of field - so color errors will be less apparent.
Both will give beautiful visual images, the triplet will probably have a slight edge for imaging - in part because it's faster so shorter exposures will be required - and in part because the extra element allows the designer to have the lens do more stuff to make a nicer image.
Personally, before buying a scope with a front element made of fluorite, I'd want to make sure the coatings they put on were adequately protecting the element - as dew would damage an unprotected fluorite element. It's probably OK, as I haven't heard of problems - but I'd scour the net to make sure folks weren't having problems before spending my money to buy one.
