See, I KNEW fluorite was the ultimate astronomical element!

[LewisM]

http://www.skyatnightmagazine.com/ne...igins-revealed



Ah fluorine... mix it with Calcium, and you have sweet, SWEET optics, and minty fresh breath.

[AstralTraveller (David)]

Combine it with hydrogen and you have the strongest acid known. It is perhaps the only thing I am aware of that will dissolve silicates (possibly boiling anhydrous NaOH also works). For this reason it is used in geochemical research. It is also incredibly toxic and will kill you as soon as look at you. It is absorbed through the skin and causes organ failure. Direct contact with even a few mL is generally fatal. [Terry in the OSL lab etches mineral grains with HF in near darkness, the red light is so faint even an experienced astronomer would find it daunting. He can keep it.]

The discovery of fluorine is an interesting and tragic tale. Researchers often accidentally actually made HF and then unwittingly exposed themselves to it. There were several deaths. Also the HF attacks glass apparatus and so it wasn't until someone built a set of pure Pt apparatus that it was isolated.

[RB (Andrew)]

Originally Posted by AstralTraveller

It is absorbed through the skin and causes organ failure.

So don't lick your refractors Lewis.

[PlanetMan]

Originally Posted by LewisM

http://www.skyatnightmagazine.com/ne...igins-revealed



Ah fluorine... mix it with Calcium, and you have sweet, SWEET optics, and minty fresh breath.

I probably misread the article but it doesn't actually discuss fluorite in refractor optics - I thought the whole idea of fluorite particle lens (ie FPL 51 53) was to get the good benefits of fluorite crystal without the hiccups (fragile, brittle, expensive, toxic etc)

[Satchmo]

Yep , Flourite is not ideal - brittle and open to moisture attack . I broke the flourite element in my Celestron /Vixen refractor when giving the dew hood a bit of tap when I cross threaded it .

[PeterEde (Peter)]

Hydrofluric acid dissolves bone from within according to a lab tech friend and the only way to stop it is amputation?

[LewisM]

Originally Posted by PlanetMan

I probably misread the article but it doesn't actually discuss fluorite in refractor optics - I thought the whole idea of fluorite particle lens (ie FPL 51 53) was to get the good benefits of fluorite crystal without the hiccups (fragile, brittle, expensive, toxic etc)

No, it wasn't specifically mentioned - just about the discovery of fluorine origins... which I branched off on. ANYWAY...

FPL53 only has roughly 20% (MAXIMUM) or fluorite in it, so it only proffers SOME of the good Fl characteristics. FPL53 still shows significantly more light scatter than a CaF2 element does. I haven't looked at O'Hara's site for a while, but I think FPL51 - the most common glass in Chinese refractors - only contains roughly 4 to 8% fluorite.

I found this iStar forum thread of interest: http://istarscopeclub.proboards.com/...-fluorite-apos

Well worth the read if you are interested in the differences between CaF2, FPL51 and FPL53 glasses.

Andrew - I make all my vodka shot glasses out of CaF2 - slamming them on the table or setting Ouzo alight is guaranteed to shatter them into non-reusable status

[RickS (Rick)]

and frankly, optical performance of CaF2 triplet is textbook perfect. If designed properly, such lens is free of all aberrations including the chromatic aberration.

Must be magical stuff indeed! Apparently, it's not constrained by the laws of Physics

[multiweb (Marc)]

Originally Posted by RickS

Must be magical stuff indeed! Apparently, it's not constrained by the laws of Physics

Nothing beats a good vodka spaced triplet.

[RickS (Rick)]

Originally Posted by multiweb

Nothing beats a good vodka spaced triplet.

Now you're talking, Marc, although I find that a 20 year old single malt offers better colour correction

[LewisM]

Uh ah - colour DISTORTION

[cometcatcher (Kevin)]

You're all spoiled nowdays. In the good old days of the wild west and pirates, we used F 100 to correct for stuff. Sometimes there was minor droop.

[RB (Andrew)]

Originally Posted by multiweb

Nothing beats a good vodka spaced triplet.

Originally Posted by RickS

Now you're talking, Marc, although I find that a 20 year old single malt offers better colour correction

Originally Posted by LewisM

Uh ah - colour DISTORTION

Hence my preference for Ouzo Doublets.

[LewisM]

You see double after an Ouzo doublet. 2 pot screamer...