Glass types

[Slawomir]

Hi all,

Out of curiosity I decided to find out a bit more about optical properties of a few common glass types used in telescope making and put some basic data in the attachment. It is quite fascinating topic and perhaps one day I will venture into polishing glass and making my own lens cell..maybe :)

P.S If you actually opened the attachment, you automatically qualified as an astro-geek :lol:

[RickS]

Now, that's just getting masochistic Suavi :lol:

[glend]

This link contains a fair bit of comparative glass, and flourite, information. Of particular interest is that Flourite no longer enjoys the advantage that it had several years ago. A good FPL-53 element in combination with other enhanced glass formulations can surpass a good Flourite setup.

http://telescope-optics.net/semiapo_and_apo_examples.htm

If you study line entries 15-21 you can see that FPL-53 combinations produce equivalent or better Strehl numbers than CaF2 (Flourite) combos.

If you have time, it is worth reading through this thread on glass on Cloudy Nights, and Eddgie's examples.
It is very hard to beat a modern FPL-53 Triplet APO.

https://www.cloudynights.com/topic/507960-fluorite-vs-ed/

[LewisM]

We agree for once, hence why I bought a Takahashi TSA-102S FPL-53 triplet :)

[Camelopardalis]

Ah but Glen, busting the Fluorite myth goes against the justification/excuses by those who suffer cloud rage ;) :lol:

What's more important is a good figure...folk get pleasing results from mirrors made from kitchenware, so it's all a question of perception/perspective.

[LewisM]

I am glad there has been no need for cloud rage in Canberra - just perfect seeing for days on end.

I'm saving for Yuri's fluorite 140mm triplet.

[Wavytone]

referring to my soup bowls ? :rofl:

[Camelopardalis]

:lol: