FreeLists / az-observing / [AZ-Observing] Re: Sunspot Group Near Meridian

[spooner@xxxxxxxxxxx (Michael Spooner)]

My 10" filter is a Tuthill (actually spans 12" diameter but the mounting
clear aperture is 10"). I have a Baader filter that has a 6" diameter and it
is terrific stuff but I've been very happy with the Tuthill film also. I
generally prefer using 150 to 300x for solar viewing but do use 75x or so
with both films if the seeing is poor - but I don't view too long unless
details are good enough to use higher powers. I prefer an annulus ring to
block light from behind the primary but even closing off the tube won't be a
major problem. With the full aperture filter, enough heat is rejected that
my aluminum tubes are actually cool to the touch after tracking for a while.
With the Dobs, I have to manually push them once in while to keep the sun's
rays at a grazing angle until I'm ready to view. The standoff on the front
is linear not radial so the light path is still completely covered (and
safe!) and the gap is only a quarter inch or even less. There isn't a lot of
light entering from the side and doesn't seem to be a problem. I haven't
done nearly the amount of solar viewing and video that I have of planets and
don't really know if there is a better time of day at my local. I suspect
mornings would offer more hope as would a day that had been cool with clouds
and cleared enough to permit solar work. Just as with planetary viewing,
solar viewing would reward diligence. Both can be frustrating when trying
for the highest resolution. Plus solar viewing with Newtonians has the
danger of 'half tan syndrome'. :)
--Mike Spooner

----- Original Message -----
From: Jack Jones <spicastar@xxxxxxx>
To: SAC AZ List <az-observing@xxxxxxxxxxxxx>
Sent: Sunday, August 12, 2001 10:51 PM
Subject: [AZ-Observing] Re: Sunspot Group Near Meridian


> 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?
>



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