What is FPL glass?

What is FPL glass?

FPL-53 ‘Super ED’ or ‘FD’ glass made by Ohara in Japan with an Abbe Number of 94.94 − less expensive and easier to work with than fluorite crystal with a very similar Abbe Number to fluorite. Chemically more stable than fluorite. Also referred to as ‘Synthetic Fluorite’ or ‘SF’ glass.

Why is fluorite toxic?

Fluorine is a relatively soluble and highly reactive found within fluorite. Exposure to the chemical can lead to a severe bone disease called skeletal fluorosis, which weakens bones.

Is fluorite toxic to humans?

12 Fluorite. The fluorite is the principal source of fluorine and used as flux in open-hearth steel furnace. The elemental fluorine above 25 ppm is highly toxic and causes significant irritation and damage to gastric-intestinal system, eyes, respiratory tract, lungs, liver, and kidneys.

What refractors are made with FPL-53?

William Optics provide the ‘ZenithStar 71 ED Doublet’ refractor having a focal ratio of f/5.9 and employing a rack and pinion focuser. At significantly higher cost, TeleVue manufacture the TV76 and TV85 2 ‘APO’ refractors that have doublet objectives which I suspect uses FPL-53 glass as one element.

Which telescopes use fpl-51 glass?

Altair Astro provide their Starwave 102ED and Starwave 110ED refractors also using FPL-51 glass as one element. Telescopes in this aperture range are now often employing triplet objectives with one element made of ED glass.

How big is the field of view on a FPL-53?

This uses a triplet objective employing one element of FPL-53 glass and, coupled with a 2-inch star diagonal and 30mm wide field eyepiece such as the APM UW ED 30 mm eyepiece, can give a true field of view spanning 5.9 degrees across.

What telescopes sell the TS PhotoLine 70mm f/6 FPL53 triplet Apo?

Teleskop Service or APM Telescopes sell the TS Photoline 70mm f/6 FPL53 Triplet Apo that comes with a 2-inch rack and pinion focuser.