Re: [ATM] infrared filters using film

[George Anderson <georgea@cam.org>]

He is using the filter to block all but the infra-red light. This is
fine for I/R imaging of nightsky objects as he is doing, and if you
don't mind the low quality of the filter.
The Thousand Oaks and Coranodo filters are a very different kettle of
fish. They are intended for solar viewing and are a very narrow bandpass
filter intended for viewing the sun.
DO NOT USE COLOUR (or any photographic film) FILM TO VIEW THE SUN!!!!
With a refractor you will most likely burn your eye in a heartbeat or
two (the film filter is letting the dangerous I/R pass at high levels),
with a reflector you will also burn your eye and probably damage your
secondary while you are trying to figure out why you can't see anything
through what used to be your good eye. Not that you will care about the
secondary anymore as your friends will call you cyclops from now on.
There is a reason that quality filters for solar viewing cost serious
coin, they are expensive to make. There is no text substitute for what
the human eye can see.

George Anderson
Montreal Canada

Clear skies and good health

"Lawrence D. Lopez Software Engineer" wrote:
> 
> My brother sent me this link.
> Please understand that it does produce pop ups.
> Basically it says that you can use color film
> (Kodacolor say) as an infrared filter.
> 
> http://www.angelfire.com/space2/tgtan/infrared.htm
> 
> What I was wondering was how imporant is the
> figure of the surface of such a filter.
> 
> I've heard of very accurate filters from Zeiss.
> I've also heard that 1000 oaks filters did not have a good figure
> and that Coronado did, and that there was some improvement.
> But these were fill arperture filters.
> 
> Can anyone shed any light on this ?
> 
> Does it matter much ?
> 
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