~~~~~ Bov, Frank said:
>Two thoughts from yesterday's digest
>
>1) Anyone ever consider how lucky we are to have someone like John Hermanson
>participating on this list? When has he ever refrained from suggesting a
>repair that was appropriate for the person posting?
Yes, a rather unfortunate bush fire I would say
>
>2) No one should ever consider solar observation through any type of filter
>without first:
>- making absolutely sure it's a 5.0 D or higher *at all wavelengths* from
>far IR to far UV
>- checking it for any defects
>
>Many filters block the visible spectrum, but UV and IR are what fry your
>eye. That's why multiple layers of overexposed color film don't work.
>Destructive testing is certainly inappropriate. Buy from trusted sources and
>check for pinholes; they can let in enough UV/IR to damage your eyesight. If
>you find them, use a heavily pigmented opaquing fluid to cover them. I have
>a solar filter for a small telescope and the inside of my filter is covered
>with little white bumps, and I add several more every time I see a hole (I
>miss a lot).
A camera shop in the UK called Speed Graphic is selling "Kood Stanford" CR39
filters in sizes from 37 to 86mm which they say are safe for 200-380nm UV and
780-1400nm IR ranges (I don't understand the wavelengths mentioned BTW).
Prices range from £15-35. Their telephone number is +44 1420 543366. I have
bought a Billingham bag from them, otherwise I have no connection with the
establishment.
Chris
><> *** Chris Barker ***
mailto:cmib@xxxxxxxxxxx
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|