Blair MacDonald wrote:

> Colour filters work well on planets. They can cut the glare and bring out
> contrast on some features.

Well, this is may or may not be <g>. Last Saturday night I had the chance
to use a couple of research instruments (6" refractor & 36" RCT) mounted
side-by-side for ~4 hours of visual use - the seeing was too poor for
imaging. During that time many comparisons were done comparing the
effects of a large variety of filters as well as stopping down the aperture.

The winner was....no filter at all. While certain colours were helpful in
enhancing one particular feature, none revealed features that were not
visible in the unfiltered view. The downside is that a material amount of
information was "lost" when using the filter. While a particular filter
may help in examining one feature it was not helpful when studying the
whole planet.

I think it was Bill Arnett (sp?) who gave the best solution - more power.
Get up to the point to where no additional detail is seen, then drop down
to your next higher power EP. In the "average" view you won't see additional
information, but during those moments of steadiness you will get a snapshot
of great clarity.

Stopping down the 36" did help up to a point. Going below 10" was no
help at all, even though the seeing was very, very bad. Even at that
point it was no help to the effects of seeing (contrary to popular myth)
nor did it help sharpness. It did noticeably help contrast, though. My
personal hypothesis on this is that the improvements do not come from
a smaller aperture but from switching to an unobstructed design.

But no matter what, get out and look! Mars is putting on a fantastic show
right now.

Gene Horr

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