Solar filters, glass

Hi. Our club has a booth at an annual May festival. The member that
normally shows up with a scope and solar filter might not make it this year.
I was thinking of just buying a filter for the club.

Now our club has a couple of scopes. A 60mm refractor, 3" O.D. and a couple
of 4" newts, both 5" O.D. Does anyone know of a manufacturer that does 3"
or 5" glass filters? Doesn't matter if it's off-axis.

Yes, we have Mylar. But I can just imagine some kid sticking his fingers
through it while looking at the sun. No, I want glass and something with a
metal ring. So I can drill some set screws, to keep the filter on the
scope...Dennis

On Sat, 10 Apr 2004 17:16:35 -0400, "Dennis Allen"
wrote:

Yes, we have Mylar. But I can just imagine some kid sticking his fingers
through it while looking at the sun. No, I want glass and something with a
metal ring. So I can drill some set screws, to keep the filter on the
scope...Dennis

Orion Telescope sells glass filters complete with metal mounting
rings. http://www.telescope.com.

A long dew cap goes a good way toward keeping fingers away.

Solar projection is the best way to show sunspots to a crowd as more
than one can look at a time. The 60 mm would be the one to use for
projection.

On Sat, 10 Apr 2004 17:16:35 -0400, "Dennis Allen"
wrote:

Yes, we have Mylar. But I can just imagine some kid sticking his fingers
through it while looking at the sun. No, I want glass and something with a
metal ring. So I can drill some set screws, to keep the filter on the
scope...Dennis

Orion Telescope sells glass filters complete with metal mounting
rings. http://www.telescope.com.

A long dew cap goes a good way toward keeping fingers away.

Solar projection is the best way to show sunspots to a crowd as more
than one can look at a time. The 60 mm would be the one to use for
projection.

How about Baader material behind glass? I can't comment on the degree of
optical abberations normal plate glass might have. I assume the thinner
and flatter, the better.

Bryan

Dennis Allen wrote:
Hi. Our club has a booth at an annual May festival. The member that
normally shows up with a scope and solar filter might not make it this year.
I was thinking of just buying a filter for the club.

Now our club has a couple of scopes. A 60mm refractor, 3" O.D. and a couple
of 4" newts, both 5" O.D. Does anyone know of a manufacturer that does 3"
or 5" glass filters? Doesn't matter if it's off-axis.

Yes, we have Mylar. But I can just imagine some kid sticking his fingers
through it while looking at the sun. No, I want glass and something with a
metal ring. So I can drill some set screws, to keep the filter on the
scope...Dennis

wrote in message
...
How about Baader material behind glass? I can't comment on the degree of
optical abberations normal plate glass might have. I assume the thinner
and flatter, the better.

Bryan

Dennis Allen wrote:
Hi. Our club has a booth at an annual May festival. The member that
normally shows up with a scope and solar filter might not make it this
year.
I was thinking of just buying a filter for the club.

Now our club has a couple of scopes. A 60mm refractor, 3" O.D. and a
couple
of 4" newts, both 5" O.D. Does anyone know of a manufacturer that does
3"
or 5" glass filters? Doesn't matter if it's off-axis.

Yes, we have Mylar. But I can just imagine some kid sticking his
fingers
through it while looking at the sun. No, I want glass and something
with a
metal ring. So I can drill some set screws, to keep the filter on the
scope...Dennis
Seriously, glass is a hell of a lot more dangerous than mylar. Have you
actually tried to put your finger through a piece of mylar film?. If it is
properly gripped round the edge (no 'sharp' gripping points), you can punch
a sheet of mylar, as hard as possible, and it does not fail. Try it with one
of the mylar balloons. Glass conversely is dangerous. If you have a
reasonably thin piece of glass, it'll break far more easily than mylar, and
give sharp edges too. If you are this worried, get the old 'single layer'
mylar film (rather than the double sides Baader material), and have two
sheets with a gap between. To let light through, requires both layers to be
broken.

Best Wishes