--- Tyler Allred <tylerallred@earthlink.net> wrote: <snip>
I don't think Ha filters are useful for visual observing. The emission line that they isolate is at a wavelength of about 650nm, which is outside the range of human night-sensitivity.
Some additional info along the same lines - The Lumincon Ha filter is intended to be photographic only, as shown in their online bandpass figures - the H-beta filter is for visual. Lumicon filter http://www.lumicon.com/filterspec_prnt.htm Photo h-alpha bandpass http://www.lumicon.com/images/lumicon%20photo%20chart.jpg Visual h-beta bandpass http://www.lumicon.com/images/lumicon%20visual%20chart.jpg - Canopus56 __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com