In your message dated: Tue, 31 Mar 1998 22:58:55 PST you write:
>Hi, I have some questions I would like to get advice on. I'm breaking
>this into a couple of parts:
>
>How significant is using teleconverters on lenses other than the
>recommended ones? I have a 300mm and I am considering buying the 2X (I
>already have the 1.4X); any opinions?
I have used the 2x-A with my 500mm mirror, 300/4.5, 65-200/4, and
180/2.8. The images are sharp and contrasty, but I've not done a
"formal" resolution test with a chart. The main thing to remember with
the 500 and 300 is that you need a *steady* tripod, especially if you
use a shutter speed slower than about 1/250th. I think a lot of folks
interpret camera shake as optical degradation.
>
>I am thinking of using the 300mm with the 2x for photographing the next
>Total Solar Eclipse to get a bigger image. Any concerns? Would I get
>better images with a portable refractor like the Pronto by Televue?
I go on these eclipses every time, to run scientific experiments to
measure the temperature of the solar corona. As it turns out, our
expedition "leader" is Jay Pasachoff, who literally wrote the book on
eclipse photography (available from Cambridge Univ. Press or Sky & Tel).
Jay uses 500/8 mirror lenses and borrowed a Nikon 600/4 from National
Geographic for this last trip to Aruba. I suggest getting Jay's book
(co-authored by Michael Covington, who is also the co-author of the
Olympus FAQ with me!).
>
>How about recommended film and exposures for the various phases of a solar
Use 100 or slower, especially since you have a good tripod. Also,
remember that the Sun moves 15 deg/hour. Thus, in a 2.5 min eclipse, it
will move about 38', or just over one solar diameter. This is small
compared to the 7 solar diameters of corona (3 solar radii on each side
+ the sun itself).
>eclipse? How to maximize exposure settings in a few minutes? I am
>thinking about getting the Quartz Intervalometer to use with my winder 2
>and an OM-4t. Opinions?
Yes, I just bought an M.Quartz Remote Control 1 for exactly this
purpose. However, remember that you will want to bracket your exposures
to get the inner corona and promenences, and the outer corona. Without
a radially graded neutral density filter (a "Newkirk" filter), you can't
get it all in one exposure.
>
>I would like to use two cameras on the same tripod for the eclipse (or one
>camera with the 300mm and the other camera with a small refractor); how
>feasible is this? I have a Bogen 3001 with a 3055 heavy ball head
>(hexagon plate). I believe there is a plate that will allow two cameras
>to be mounted on a single tripod head. Or should I get the "Side arm" or
>"Double head support"?
We ran 3 cameras on the same tracking mount in Aruba, and it worked
fine. Just make sure shutter vibrations don't get transmitted between
the two cameras.
>
>I find the 300mm hard to focus at infinity (since it focuses past
>infinity) with the 1-10 grid screen. Any recommendations for a better
>screen to use?
Beattie screen. I plan to get one of the new ones with angled focusing
aid and grid. They're about $65 from B&H.
Cheers,
--Lee
>
>
>Thanks, John
>
>
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