I've heard that the full aperture method makes the image way too bright with
this film, at least for observing and with 8 to 14 inch ap. Masks must be
painted white or they will heat up. White keeps everything nice and cool. Maybe
high magnification got a bad name in the past? Observing with high
magnification may now be easier with the Baader film. I'm not sure if this is a
factor. How do you remedy reduced contrast from gaps around the mirror? Is it
safe to cover the back of a Newtonian for long periods when viewing the sun? I
usually view only in the morning for short periods, but there are public events
that go all day. Also, can you explain why gaps at the back of a Newtonian
reduce contrast and then you use a standoff at the front which could do the
same thing?
Jack Jones
I tend to prefer full aperture solar film (at least to 10" that I've tried).
A couple of benefits include cooling the scope by reflecting the heat
instead of absorbing like some masks and I find that 4" or so doesn't allow
enough brightness at high power when the seeing allows. This also allows for
better saturation when I video the images. Also note that light leaking from
the back around the edge of the mirror will destroy the contrast in
reflectors. If you think high magnifications can't be used for solar
viewing, I have some Mercury transit video that is not too shabby. Don't
think the seeing is much worse in this later millennium. :)
It does take persistance but daytime viewing can allow some very good
images. With Newtonians, I mount the filter on standoffs to permit venting
at the upper end of the tube.
--Mike Spooner
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