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Hello Paul,

I don't consider Davis's original filters safe for solar observation at all.
David Burch's book describes a method for measuring index error (The Solar IC method). For this, he describes a small "cap" that needs to be slipped over the end of the telescope. It's made of cardboard and uses a Baader AstroSolar filter. Based on that, I made my own, but from a plastic film canister cap.

I want to make a better one for the Astra sextant.
According to Google, this is the official name of what I bought (available in multiple sizes):
"25-64mm Rifle-Scope Hunting Aiming Optic Lens Covers Telescopic Flip Up Spring Protection Cap Dust Cover"

I’d drill through the top and glue an AstroSolar filter into it. 

For the Davis sextant, I cut out one shade and glued AstroSolar filter inside.
But the final solution will be to completely remove the inside of two shades and glue the filter between the frames of the two shades.

Bela

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