Total
Lunar Eclipse on May 15-16,
2022
Preliminary Findings from Observations
Helio C. Vital
(1)
Was the eclipse dark? Yes.
(2)
Was the eclipse extremely dark? No.
(3)
Was the Moon at mid-totality
approximately as dark as predicted based only on its path across the umbra?
Yes, roughly. Probably, a
bit darker though.
(4)
What were the estimades made
by the Brazilian
Team of observers
for the brightness of the Moon
at mid-totality? Preliminary means for Danjon and magnitude estimates made by Brazilian observers
consistently indicated a relatively dark eclipse.
They were: L=2.0 (±0.5) and m= -0.8 (±0.3), respectively.
The author`s estimates for mid-totality were: the Moon was
roughly 1.8 times brighter than Alpha Centauri
and ~4 times brighter than Antares.
Both comparisons yield m=-0.8±0.2. He chose to assign different Danjon (L) Numbers to the Southern (brighter,
pale orange
colored) and the Northern (darker
and mostly colorless) parts of the Moon`s
disk. They were: 2.5 and 1.5, respectively. Since the selected
areas covered 45% and 55% of the
disk, his estimate for the Moon was:
L = 2.5 x 0.45 + 1.5 x 0.55 = 2.0
The observers were: Alexandre Amorim,
Willian Souza, Helio C. Vital, Antonio Padilla, Caio Correia, Cledison Silva,
Luiz A. Araujo, Niercey Justino and
Paulo Fernandes.
(5)
What would be the magnitude of the Moon
at mid-eclipse if the stratosphere were free of aerosols?
A correlation derived by the author
provides the mid-totality visual magnitude of the Moon for a
given umbral eclipse magnitude. It is:
m(U) = - 2.0765*U2 + 10.334*U -
11.70 (Vital, Helio C.)-----
Based on data from 11 observed eclipses with clean stratosphere (r2=0.999).
For the umbral
magnitude U=1.415 of the
eclipse, it yields m=-1.23.
(6)
Why was the eclipse unusually dark? Because the
Moon penetrated deeply into Earth`s umbra, more than in most eclipses. Due to the fact
that the inner umbra is darker, less sunlight reached the Moon there.
(7)
The additional darkening of the
Moon of only
0.4 (±0.3)((=1.2-0.8) magnitude could be attributed to Tonga aerosols? Possibly. In case it was indeed caused by
Tonga aerosols it would be more compatible with a VEI (volcanic explosivity index)=4 eruption 4 months ago, rather than a VEI=5 (on which the author
had based his estimate). However, since the magnitude difference is very small, it could also have been
caused by excessive cloudiness along Earth`s limb
or uncertainties in the correlation and/or also
in the observed magnitude. For
example: Tony Mallama`s prediction was m=-0.5, for this eclipse. That would eliminate the need for any
volcanic effect at all. However,
the author still favors the assumption
that Tonga slightly darkened the eclipse, considering the huge amount of
material still lingering in the
stratosphere and producing amazing color displays at twilight worlwide.
(8)
The darkening effects of Tonga aerosols will
also be observed
during the lunar eclipse in
November? Volcanic aerosols can linger in the
stratosphere for many months. However, with basis on
what happened during the eclipse in May, the author
expects the effect from Tonga`s eruption to be very small (possibly 0.2±0.2) during
the total lunar
eclipse of 2022 November 08.
On the other
hand, since the eclipse will
also be central, he predicts the
Moon will be shining at
m= -1.3±0.5 at mid-totality
if no other stratospheric eruption occurs. That would
also correspond to a moderately dark eclipse.