Re: [APML]: Color Film and Filters

[aa6g@aa6g.org (Chuck Vaughn)]

>        The Ultrablock filter is advertised as a visual filter only-not for
>photography. Are you saying it CAN be used for photography? 

Well you _could_ .... but most nebulae don't have nearly as much OIII
emission as they do H-alpha. The ones that have high OIII emission are 
easy to see (M8, M42, M17) and you would be able to photograph them 
through an Ultra Block filter, only on Tech Pan of course. All those 
nebula that are easy to photograph but hard to see (gamma cygni for
instance) have a very low OIII emission. The light pollution would still
get you on those.

If you could find a UHC filter with high transmission at H alpha and I'm
not sure any of them do, you could try that for astrophotography. That would
cut out a lot of light pollution, much more than a Deep Sky.

Chuck  <aa6g@aa6g.org>