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Post Info TOPIC: Filter thread


L

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Filter thread
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Spoiler

Test of two filters at the extremes of the solar spectrum, a Wratten #25 Red filter and a Calcium-k line ultraviolet filter.

Images captured with a 100mm refractor and Vesta pro webcam +Baader solar filter + IR-cut filter.

Music generated on an Amiga 1200



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L

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Thread measurements
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 Thread measurements of astronomical Equipment 

Each manufacturer of astronomical equipment prefers its own special adaptors. This summary is far from being complete (and correct)
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SCT thread: 2"x24tpi



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L

Posts: 130085
Date:
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Most eyepieces nowadays have threaded barrels to accept filters.
Quality diagonals also may have threaded barrels, (which is convenient, as you do not have to swap filters when changing eyepieces).
Quality filters should also be 'stackable' allowing two or more(?) filters to be used at the same time.
The problem is that there is no real 'industry-standard' size for 1.25" (31.7mm) barrel threads; so the filter threads could either be 28.5 or 28.6mm x 0.6mm pitch, (or even 1.125" x ~44 tpi threads).
Things are better with 2" filters which should universally accept 48 x 0.75mm threads.

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