Re: Venus issues

On Wed, 07 Mar 2007 20:05:01 GMT, "Steve & Lizzie"
<steveandlizzie@xxxxxxxxxxxxxxxx> wrote:

Dear All

I have been told that I should be able to resolve Venus
easily - what am I doing wrong?

All the replies that I've seen are very good, but maybe I could point
out, in addition, that what you are describing is pretty much the
typical view of Venus in an amateur telescope, most of the time...

When you were told you could "resolve" Venus, what exactly did that
person mean? Did they elaborate? It's a virtual certainty that
almost no one sees any detail other than a bright, shimmering blob, or
sometimes crescent, a visual mess. Some very few astro-imagers have
been able, with special filters, to get a detail here and there of
cloud cover reflection variations. Going back into history, there was
a notorious American astronomer from the turn of the 20th century
named Thomas Jefferson Jackson See, who claimed to have been able to
spot many things on Venus. He wasn't believed at the time, and today
the best guess is that he, like Percival Lowell, was mistaking some
kind of optical illusion for perceived details (though he did make
some darned good double star observations that were doubted for
decades, until he turned out to be right about them when modern
techniques confirmed his measurements.) See was just about the only
person I can recall reading about who "saw things" on the surface of
Venus; now we know that clouds cover it all the time and the
reflectivity is so high, with such bright sunlight bouncing back out
from the tops of the clouds, that the Earth's air creates a havoc of
the light from Venus that reaches down through our atmosphere.

Because Venus is essentially such a dull, boring, predictable thing in
a small amateur telescope, I rarely look at it. The last time I did
was to test a friend's 127mm Orion Mak scope, and to get his
collimation done correctly and align his equatorial mount. I finally
managed to get it to track, and the optics sharp enough to show a
wildly shimmering crescent, blindingly bright, with surprisingly sharp
"cusps"; but those things are no better seen in my C-11 telescope, or
any other one I've ever used for such an observation.

So, chalk Venus up as a worst-case item for planetary observers. Like
Mars (at closest opposition) it's too bright, and breaks down rapidly
in less that absolutely perfect "seeing". But unlike Mars, no matter
what you try, how long you look, or how often, you'll get no further
with Venus. Saturn's the thing at the moment, anyhow!

AstroApp
.

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