[APML]: Tri-Color Update

[charles@jon.cjfny.org]

A couple of months ago I announced my intentions to do some tri-color
work. However, Michael, among others, suggested that there may be
problems with telephoto lenses or refractors as far as the blue filter
shots. Apparently (and this was suggested as well) a light yellow (minus
violet) filter will eliminate blue fringing, and this was also recently
confirmed to me by someone who has tried this approach. So I am hopeful
and plan to start this spring.

I have noticed that the traditional green filter (#58) is not sensitive
to the OIII emission lines. Has anyone tried other filters to deal with
this? I would like to avoid using gels, and prefer glass filters. A
green-blue filter would do the trick, but no such glass filters are
available, and I am not sure if Kodak still makes many of their
traditional Wratten gels.

Charles