On 2012-05-23, Jon Anderson wrote:
I shot the eclipse with my Sony A700, and a Perkin-Elmer 800mm
catadiptric lens. Only thing I had that would cover that were my gold
coated full face lenses. I did some test shots in my driveway mid-day to
try and get a handle on shutter speeds and such (since the lens is a
fixed f/11), and noticed that after only a few minutes of experimenting
trying to get an idea where I needed to be for the actual event, my
right eye was starting to get that scratchy eyeball feeling most welders
have experienced.

Did you do what is recommended for mirror lenses -- make a cover
for the front, with a small (say 1" diameter) hole off center so your
actual aperture is significantly smaller that f/11. That might have
gotten you down to f/32 or so. One reason for this is to minimize the
heating of the central mirror which can otherwise be damaged by the heat
from all that sunlight. (And it also lets you use a less dense filter
-- you might have been able to get away with a #10 or so.

I ended up shooting through a #13, ISO 160, at 1/4000 sec.
Here's 6 of the best:
http://www.flickr.com/photos/10986502@N08/sets/72157629865291990/

BTW -- any idea where the multiple rings on the thin side of the
image came from?

Obviously late WRT to the eclipse, but for someone wanting to view or
photograph the Venus transit, this might give a clue what you're going
to need to dim the sun enough to see Venus against a full sun. I don't
think a welding lens is going to cut it for the Venus transit. Search
ebay for 'solar filter', there's special films available pretty cheaply
that blocks 99.9999% of visible light.

And -- use that off center aperture to cut it down even more and
protect the internal parts of the cat lens.

Enjoy,
DoN.

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