Ancient
Lunar Eclipses
DRH
1967
The Author
Crater Schmidt
Eclipse 20070828
2007
December 24
by Byron Soulsby
Isabella Plains Lunar Observatory Australia
Julius F J
Schmidt
1842-1879 Lunar Eclipses
In
1924 Willard J Fisher published a copy of Schmidt's manuscript of 1880,
Beobachtungen der
Mondfinsternisse
An
Introduction (translated
from the original)The
reports on lunar eclipse observations include many which are already
known. Some of the telescopes used were of inferior quality and used
only slight enlargements [magnification]. To obtain the enlargement
coefficient numerous observations of entry and exits of good visible
spots on the Moon's surface have been noted. In 1852 Schmidt worked on
calculations on the enlargement of the shadow radius using Mudlers
Rule, he also used a shorter approximation. How the different entries
and exits on the washed-out border of the penumbra
were
estimated can be seen in the value C (the value of the enlargement of
the Earth's shadow radius, where 1/C = %E * 100).
Two
measurements made of the width of the shadow made at Olmutz and Athens,
using thread micrometers were unbelievable and are not recorded in the
original manuscript. The following observations show from the
author's own observations, how long before and after the end of the
lunar eclipse the shadow radius could be seen with the naked eye.
The
average was 26 minutes before the beginning and 19 minutes after the
end of the half shadow could be observed. In reality both times should
be the same, however the eye was already too tired and insensitive to
observe the last part of the half shadow.
Partial
eclipse 1842 January 26
Eclipse
of the Moon observed by J Schmidt since 1842. This was first seen by
the author and he used a Dolland telescope with 20 times enlargement [magnification]
and
noted the time using a pocket watch (which was not very accurate). The
eclipse started early, the Moon was near the horizon and the eclipse
looked elliptic[al]. At - 7o
Re'
the air was absolutely clear and 28 entries and 28 exits were recorded.
The author could not recall which moments of entry and exits he
observed, however he thought it was the middle phase. The duration of
this eclipse was 2h 54 m [the time from 1st to 4th contact was
2h53m03s], the size of the northern shadowed part was 9.75 zoll [inch?].
[This
eclipse was observed with two others, Madler and C. Rumker. The 1844
May 31 eclipse was observed with 7 other astronomers, but the crater
timings were not attributed to individual observers].
Shadowed
observation report
The
Moon could be seen at 4u 20m with the border already in milky, smoky
shadow. The spots [craters] could be seen clearer 1/4 hour later. After
the Earth's shadow darkened Aristarchus, Grimaldi and Sinus Iridium
[were seen], the dark part of the Moon was brown red coloured and many
more spots were visible.
Reduction
of the many crater timings by Schmidt have been made using my crater
timing reduction programs.The original
manuscript
contains long descriptions of various eclipse phenomena, with
hundreds of crater timings and has special merit of being the
comparative record of 38 years of lunar eclipses, all seen by the same
expert eye [1].
To obtain
comparative
accuracy in my reductions, the method of time keeping in the 19th
century was investigated as it is known that time was counted from
noon. A study of Sundials
Australia,
by Margaret Folkard and John Ward gave a concise explanation of
correction to sundial solar time as Mean Sun Time = True Sun Time (or
Solar Time) + an Equation of Time Correction. A similar approach was
used to produce an equation of time correction chart for each
observatory used by Schmidt, and this has been applied to all of his
crater timings.
Once
corrected, the 28
lunar eclipses observed by Schmidt have been analysed for umbral
enlargement (%E), mean error (me) and where
possible, the
observed umbral oblateness (Fo).
Recently,
improvements
made to my Topocentric
Umbra
semi-diameter computer program has made it possible to produce Excel
charts of the estimates of its size for each eclipse as Fi
and
the slope angle
delta.
Here is one
example of
this analysis:
The data obtained has been included in my web pages in the Lunar Eclipses Finder under the link Lunar Eclipses-Schmidt.
Conclusion
The
observations made by
Schmidt provide an opportunity to compare 19th century properties of
the umbra with modern values. Such a comparison has been made here.
The
National Observatory of Athens as it appeared in March 2006. This is
where Schmidt conducted most of his observations of lunar eclipses
while he was Director of this observatory 1858-1879.
Further
Reading
[1] An
excellent
description of Julius Schmidt and his book about lunar eclipses is
given in Joseph Ashbrook's Astronomical Scrapbook, Sky
& Telescope, March 1977,
pages
173-174.
Acknowlegments
I am obliged
to the Smithsonian
Astrophysical Observatory for a copy of
the
original manuscript from Donna J Coletti, Assistant Librarian, Center
for Astrophysics Library, received January 3, 1990.
I am also
grateful to
Anna (DSTO) for her translation notes from the original manuscript, of
23 March 1990, which forms the introduction to this paper.
APPENDIX
Details
of Schmidt's first Lunar Eclipse
A movie made
of the
18420126 eclipse produced by RedShift on an iMac gave this first frame:
This is the
beginning of
the first eclipse observed by Schmidt from Eutin, Germany (Lat. 54o08'27" N,
Long. 10o35'57"E, alt.
110 feet
from Google Earth).
An interesting
thing
about his very first lunar eclipse was the position of the Moon just
after first penumbral contact as shown here. The Moon was at a very low
elevation of only 0o17'46" as can
be seen
from the local horizon (in green), but even so Schmidt reported
observations from 4h44m (or 3:44 UT). This image is at a magnification
of 30, where Schmidt used a Dolland telescope at a lower power of 20X.
As the eclipse
progressed Schmidt reported two primary contacts and 28 crater
entrances and 28 exits, finishing at fourth contact at 7h38m, a total
observing time of just under 3 hours - an excellent first observation.
Schmidt did
make
estimates of enlargement coefficient of the umbra, given as C in his
manuscript. For his first eclipse the value of C varied with each of
the three observer's crater timings. For Schmidt's 18 timings, C =
1/48.2 (or %E = 2.075), for Madler's 16 timings C = 1/49.1 (or %E =
2.037) and for Rumker's 8 timings, C = 1/57.9 (or %E = 1.727) an
average of 1.946%. It is not clear from the manuscript which type of
timings were used, but the average value of %E is close to that given
in the table for immersions.
My
reduction of his
crater timings are compared with modern predictions.
CRATER
TIMING REDUCTIONS FOR 18420126
Immersions
|
OBS
|
No
|
%E
|
me
|
1/Fo
|
|---|---|---|---|---|
|
Schmidt
|
23
|
1.8987
|
0.1462
|
370
|
|
Predict
|
234
|
2.3875
|
0.0035
|
102
|
Emersions
|
OBS
|
No
|
%E
|
me
|
1/Fo
|
|---|---|---|---|---|
|
Schmidt
|
27
|
2.2595
|
0.1483
|
42
|
|
Predict
|
233
|
2.2252
|
0.0094
|
102
|
DATE:
01-28-2007 AT TIME 14:40:02
1/Fo
is the observed umbral oblateness.
Produced by the Isabella Plains Lunar Observatory Australia, 2008 March 6.
Produced by the Isabella Plains Lunar Observatory Australia, 2008 March 6.