Quote:
Originally Posted by Atmos
"Once you go Tak yo never go back."
"Fluorite is the only form on glass."
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My search suggests, that there are not many telescopes using crystalline fluorite, most using the high-fluoride glasses. Exceptions are the older Takahashi APOs and TEC APOs. Interestingly, Takahashi seem to have stopped using fluorite because the mating element glass contained a lot of heavy metals (and because the fluorite blanks became so expensive), and Flourite is relatively soft.
Many manufacturers are now using FPL-53 glass, i don't think TAK can claim the high ground there.
How many of the Taks listed in this thread are the heavy metal Flourite variant and how many are simply the now common FPL-53?