by Helio C. Vital
Analyses of Midcrater and Limb
Timings
Dimensions of the Umbra
Our analyses of 61 selected timings made by 3 skilled observers of the Observational
Astronomy Network have yielded the following umbral enlargement factors:
1.76+-0.05% (immersions) ; 1.61± 0.06 % (emersions) and 1.691+-0.039%
(overall), equivalent to a 1.21+-0.03% increase in the lunar parallax and
corresponding to a mean altitude of 77
± 3 km for the optically active edge of Earth`s atmosphere. That figure is significantly lower than our
current overall mean of 92 km. Would that be an indication that the eclipse
was effected by higher-than-normal atmospheric concentrations of ozone that
could have caused the umbra to shrink or should it be attributed to
experimental data straggling solely? The data set also provides a range for the
oblateness of Earth´s atmosphere: between 1/397 and 1/65 (2 standard
deviations) with 1/111 being the
most probable estimate. Considering that immersions and emersions
probed low and middle latitudes respectively, such oblateness value that is
significantly higher than that for the geoid (1/298) would explain (at least in
part) why umbral enlargement factors have been found to be lower during
emersions.
Analysis of Magnitude and Danjon
Estimates
Eclipse Brightness
The brightness of the totally eclipsed Moon is primarily determined by
how deeply it is located inside Earth`s umbra. In addition it also depends on
the global levels of aerosols cast in the stratosphere by strong volcanic
eruptions. Our correlation relating
eclipse magnitude to the Moon`s brightness at mideclipse predicts mag=-1.7 for
that eclipse indicating a moderately dark event. Visual magnitude and Danjon number estimates made by 13 REA`s observers have been analyzed. The Moon´s magnitude at mideclipse has been
averaged as -2.2 ± 0.2, which is half a
magnitude brighter than predicted. That indicates that Earth`s atmosphere is
currently clear of volcanic dust. The minus -0.5 deviation probably indicates
that the current global stratospheric level of
aerosols is even lower those used to define the "clean" level
of the correlation. The brightness of
the eclipse on May 04, 2004 also showed a similar result. Those findings
suggest that Earth`s atmosphere has remained unusually clean since then.
REA`s Eclipses Site: Lunissolar
See the Effect of the Eruption of Mount Reventador on the Lunar Eclipses in 2003
Observational Astronomy Network (REA/BRAZIL)