Joe, the same safety measures apply to glass filters, where the metal is deposited on glass instead of mylar. If the holes and streaks are extremely small and few in number, there is probably no reason to be concerned. If larger, they should be opaqued. My own Thousand Oaks steel-on-glass filter has those same flaws, and it arrived like that from the factory. Glass solar filters are not made of a dark glass, like a welder's glass; they typically use steel or nickel evaporated onto a clear glass substrate, much like a telescope mirror. Install the filter on your telescope, and aim it at the sun with no eyepiece. If you can't detect any pinpricks when looking through, there's probably nothing to worry about. Chuck --- Joe Bauman <bau@desnews.com> wrote:
I have some of those glass-plated solar filters. Is there a worry about them too? I looked at some under strong light and a couple seemed to have extremely light scratches on the glass, not really scratches, just like marks where they were cleaned. When I looked at the sun with them I saw nothing odd. What's your take on this, Chuck? Best, Joe
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