[AZ-Observing] Re: [amastro] Re: Daytime Venus Viewing
- From: Brian Skiff <Brian.Skiff@xxxxxxxxxx>
- To: amastro@xxxxxxxxxxxxxxx
- Date: Sat, 5 Jun 2004 14:59:08 -0700 (MST)
John DeDecker and I also were viewing Venus starting at 20h UT (June 5)
with the Lowell Clark. Nominally 4.0-deg elongation and about 0.2 percent
illuminated. It took us most of an hour to find it due to the (analog) setting
circle slop, stiff mount, etc. We couldn't be sure even that the eyepiece in
the main telescope was in focus. We got it first in the 15cm/6-inch finder
(this is an older Clark refractor, about 90x). As with Tom's experience,
offsetting from the Sun worked best (rather than from Mercury, Aldebaran,
Betelgeuse, or Sirius), and we were able to see it in the Clark's 50mm finder
(about 10x), though the scattered light was serious for that optic.
By judiciously shifting the dome shutters our best views (EXQUISITE! by
the way) were with the main telescope stopped to about 25cm/10-inches but
about half obscured by the dome shutter. Also, since folks ask, the eyepiece
that seemed best was an 80mm Celestron (120x) with a light orange filter
(a much redder Wratten 25 was not as good). John is convinced he's seeing
illumnation all the way round, but contrast is very low, so I couldn't convince
myself it wasn't illusory. The ring certainly goes at least 270 deg around,
maybe 315, with that hint of a full circle at times. The part that's brightly
illuminated is distinctly shorter than two days ago when we did this before.
The perfect white thin crescent is gorgeous against the blue background.
A batch of a couple dozen turistas on the daily observatory tours all got
to look as well as a number of Lowell staffers who live here on Mars Hill.
Tom Polakis' webcam shot gives a good impression of the instantaneous view,
very jittery due to the seeing. In our case, the refractor objective was
looking at the edge of a metal panel of the dome shutter only 40cm away that
had been in the Sun all day (only a few scattered cumuli here, 10 percent
humidity---welcome to Arizona).
If you have good weather wherever you are, I would highly recommend
trying to find Venus if you have good baffling, and/or a way to shield
the telescope from direct Sunlight, even if it partly blocks the line-of-sight
of the telescope. You don't need much aperture. Of course, be extremely
careful. Extremely careful.
\Brian
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