[AZ-Observing] Fw: [amastro] Two-foot Diameter Pinhole Crescents and Endless Baily's Beads
- From: "Wayne (aka Mr. Galaxy)" <mrgalaxy@xxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Wed, 23 May 2012 21:48:40 GMT
Benson, AZ 85602
hm ph: 520-586-2244 Here's a good report talking about Baily's Beads and why
it's sometimes a good thing _not_ to be on the centerline of an annular
eclipse. As opposed to our several seconds worth of seeing beads, his report
says that they saw them for several minutes.
Clear skies,
Wayne (aka Mr. Galaxy)
---------- Forwarded Message ----------
From: alan whitman <alandwhitman@xxxxxxxx>
To: Amastro <amastro@xxxxxxxxxxxxxxx>
Subject: [amastro] Two-foot Diameter Pinhole Crescents and Endless Baily's Beads
Date: Wed, 23 May 2012 09:34:50 -0700 (PDT)
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Two-foot Diameter Pinhole Crescents and Endless Baily's Beads
Jim Failes had worried that we wouldn't find a suitable deciduous tree in the
Nevada desert to project pinhole crescents. But we parked in the shade of a
large elm at the Lund, Nevada school. Soon Jim noticed that the elm was
projecting huge 2-foot diameter pinhole crescents onto the wall of the school!
I paced the distance and found that the tree was 170 feet from the wall,
allowing a sight that could only occur with a low eclipse. Jim and Richard
Christie took many photos of the pinhole crescents and pinhole annulus, while
Dennis Krause and I remained at the eyepiece through our 4 minutes and 2
seconds of annularity.
We had planned to be about 20 miles inside the northern limit as a compromise
between a reasonable annulus and maximizing the duration of beads. But the
sudden blossoming of large numbers of small cumulus clouds convinced us to
drive further south to much clearer skies at a point about 45 percent of the
way from the centreline to the northern limit of the path. By annularity that
cumulus to the north had flattened out to form altocumulus covering most of the
low northern sky towards Ely, but our site was otherwise almost clear.
Although the second contact beads were brief, the Baily's Beads after third
contact were marvellous, going on and on for 3 minutes and 42 seconds after
annularity ended. Jim's tape-recording has me calling out 36 beads after third
contact, including a beautiful string of five early on.
Other highlights were the eight prominences in Richard's hydrogen-alpha scope
including a nice triple, watching five sunspot groups being slowly occulted by
the serrated black lunar limb between first and second contact, Venus becoming
prominent 16 minutes before annularity, the marked eclipse-cooling, and the
sharpening of shadows which occurred surprisingly early during the partial
phases (about 30 minutes before annularity which is much earlier than I recall
happening during the partial phases preceding total eclipses).
The Nevada high desert sky was exceptionally transparent – there was
absolutely no whitishness due to aerosols beside the Sun. Seeing was steady
enough to see granulation at 100x with my 80mm apo refractor before first
contact, but by annularity the Sun had sunk down to about 17 degrees altitude
with the result that I used only 30x for annularity and Baily's Beads. So the
nearly four minute bead show after third contact probably would have included
even more than the 36 beads seen if the Sun had been higher in the sky, which
would have allowed better seeing and higher powers to be used.
That evening we drove 4 miles south of our Ely motel so that Richard could have
his first view of Omega Centauri in 10x50 binoculars and an Astroscan. Richard
and Jim also had their first views of Centaurus A with the same equipment.
A great eclipse with great travelling companions on our five-day 2000-mile
drive from southern British Columbia. (The pies at Shari's restaurants in
Oregon and Washington are highly recommended.)
Alan Whitman
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