TOPOCENTRIC
UMBRA COMPUTATIONS
by Byron Soulsby
Theodore Lunar
Observatory Australia
Introduction
My computation program (ILEEP.exe) used to produce the Circumstances
for each of the lunar eclipses studied from 1842 to the present has
been modified to cater for individual observing sites. In my case I
have observed lunar eclipses in Elizabeth, South Australia from 1950, in
Weston, ACT from 1970, in Paradise, South Australia from 1990, in
Calwell, ACT from 1993 and recently from Theodore, ACT from
2002.
Ancient observations made by Schmidt from 1842 to 1879 were conducted
in several sites in Western Europe which included Eutin, Hamburg, Bonn,
Olmutz and Athens.
Method
Google Earth has been used to locate each observing site for both
observers and my site.loc file has included this data. This enables the
modified program to compute the Topocentric Umbra for each observer
from all appropriate sites.
Another program (ViaX7.exe) has been developed to analyse up to 40
frame coordinates
for any eclipse for values of the semi-diameter of the
Topocentic Umbra (Fi)
and the slope angle (delta). This is illustrated in the Excel chart
below for an early eclipse which I observed in Weston ACT.
Chart for 19780324
