Brad,
Many thanks for your prompt response. Yes, as you found, my old shipmate
will now easily calculate the day on which the sun's upper limb was just
not visible in April 1911, taking into account refraction and
semi-diameter. Scott's Hut is at 77deg. 38'S, 166deg. 24'E. Scott's
party kept time as GMT + 12 hours.
My shipmate and I were together in 1945 and I discovered him, now a
retired captain, living locally, 55 years later. He retains a keen
interest in astronomy.
Frank
On 27/04/2011 18:25, Brad Lufkin wrote:
Frank:
if you ignore diffraction and treat the Sun as a mathematical point,
the first day the Sun was not visible at Scott's Hut in 1911 was 24 April.
On the other hand, if you take into account both diffraction and the
size of the Sun, then the first day of non-visibility is 26 April.
Regards, Brad
On Wed, Apr 27, 2011 at 11:52 AM, Brad Lufkin
<bradley.luf...@gmail.com <mailto:bradley.luf...@gmail.com>> wrote:
Frank:
not sure how your shipmate is going about his calculations, but on
20 April 1911 at 12:00 UTC, the declination of the Sun was 11.225
degrees. This value is based on the highly accurate VSOP87D theory
for the position of the Sun and expressions for the nutation and
obliquity of the Earth adopted by the IAU.
BTW, what are the longitude and latitude of the hut?
Regards, Brad
On Wed, Apr 27, 2011 at 10:58 AM, Frank Evans
<frankev...@zooplankton.co.uk
<mailto:frankev...@zooplankton.co.uk>> wrote:
Greetings, fellow dialists,
An old shipmate asked me if the date of the start of winter at
Scott's Hut in Antarctica in 1911 could be found. I at once
thought of those wise people, the sundial group! He needs the
sun's declination for any single date close to 20 April 1911.
He knows the latitude of the hut and can easily work from there.
Seems he has found two declared dates for the onset of winter
in that month in historical accounts and they don't agree.
Presumably, disregarding small corrections for dip and
refraction, winter starts when the sun's centre reaches no
higher than the horizon. This is the value he wants.
The recent BBC programme on the conservation of Scott's Hut
and its contents was very good.
Frank 55N 1W
---------------------------------------------------
https://lists.uni-koeln.de/mailman/listinfo/sundial
---------------------------------------------------
https://lists.uni-koeln.de/mailman/listinfo/sundial
