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Old August 2nd 03, 09:12 AM
Paul Schlyter
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Default measured difference in azimuth of Sun?

In article ,
Odysseus wrote:

Aditya Naredi wrote:

Hi everyone,

A few days back I heard from my hometown in India that people
observed a 'northern shift' of Sun during sunrise. This happened
around July 17th (2003). Unbelievable as it seemed, I proceeded to
measure it myself as follows..

[snip]

Can someone please measure Sun's azimuth at their places and let me
know if it differs from calculated azimuth or not? If it is, what are
the possible explanations? If not, what am I doing wrong?


The first thing I'd suspect is that the sunrise positions you looked
up were just the "geometrical" azimuths. Atmospheric refraction and
other effects not included in such figures can make a very large
difference to the observed position. Moreover, I imagine that looking
north-east from Seattle the horizon is pretty mountainous; you might
do better trying to observe sunsets over the Juan de Fuca Strait.


He didn't measure this at sunrise - check his data:

# Data:
# Magnetic declination in Seattle (19 degrees East)
# Place Seattle, WA USA (122 20 W, 47 38 N)
# Calculated data taken from the website: http://aa.usno.navy.mil/data/
# (US Navy?)
#
# I was careful the measurements were taken in a magnetic influence
# free environment.
#
# Date Time Measured Calculated Difference
# (with True North) (from website)
# ----------------------------------------------------------------
# 07/29/03 15:30PM 235 degrees 250 degrees 15 degrees
# 07/30/03 10:46AM 124 degrees 140 degrees 16 degrees
# 08/01/03 16:40PM 250 degrees 264 degrees 14 degrees

The Sun doesn't rise, or set, at 15:30PM, 16:40PM or 10:46AM in July
at 47 deg N latitude....

Since his discrepancies are all near 15 degrees, my first guess is
that he made a "one hour mistake": either forgetting to account
for Daylight Savings Time, or by mistake choosing the wrong time zone.

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