CIRCUMSTANCES FOR THE 2015 SEPTEMBER
27-28 TOTAL LUNAR ECLIPSE
Helio C. Vital
GLOBAL CIRCUMSTANCES
On September 27-28,
Limb Contacts
|
Contact |
Universal Time
Coordinated (UTC) |
|
P1 - PENUMBRAL ECLIPSE BEGINS |
00:11:39 |
|
FIRST PERCEPTION OF PENUMBRA |
≈00:45 |
|
U1 - UMBRAL ECLIPSE BEGINS |
01:07:02 |
|
U2 – TOTAL ECLIPSE BEGINS |
02:11:12 |
|
MAX - GREATEST ECLIPSE |
02:47:17
(Magnitude=1.277) |
|
U3 – TOTAL ECLIPSE ENDS |
03:23:22 |
|
U4 - UMBRAL ECLIPSE ENDS |
04:27:23 |
|
P4 - PENUMBRAL ECLIPSE ENDS |
05:22:49 |
Probable Mean Error (1σ) in the Calculation of Contact
Times: ±9 sec
MEASURING THE UMBRA
Crater Contacts
Analyses
of observed contact times can be used to determine the size of the umbra, which
varies significantly from one eclipse to another and sometimes even during the
eclipse itself. As craters enter the umbra, regions at the top of Earth`s
mesosphere over a region at mid-southern latitudes (-42±17°), centered around
longitude (60±8)°E (Indian Ocean, just East of Africa)
will be probed. Likewise, as craters exit the umbra, mesospheric regions over
an extense region over the equator (-6±17°), centered
around longitude (150±8)°W (Pacific Ocean, West of Southern America) will be
mostly casting light patterns onto the lunar screen. By recording the time when the border of
Earth`s shadow crosses the center of the most
prominent features on the Moon, you can help us measure the umbra. The dynamics
of periodic and random wave disturbances at the top of the mesosphere (mesopause) cause variations in the size of umbra. Based on
findings from the eclipse on April 15, 2014 and also on results from analyses
of images of the April 4, 2015 event, Earth`s radius was increased by 1.27%
during immersions and 1.23% during emersions in the calculation of contact
times. Such extrapolated figures slightly exceed the minima in our statistics
of nearly 30 lunar eclipses. In addition, contact times for the most
conspicuous lunar features are provided below so that you can plan your
observations. The mean difference between such predictions and timings made by
experienced observers has been determined as ± (0.3±0.2) min.
Immersions
|
Crater/Feature |
UTC |
Umbral Angle (°) |
Crater/Feature |
UTC |
Umbral Angle (°) |
|
Limb (U1) |
01:07:02 |
-36.5 |
Menelaus |
01:42:13 |
-38.1 |
|
Riccioli |
01:09:24 |
-42.2 |
Tycho |
01:43:30 |
-60.3 |
|
Grimaldi |
01:10:51 |
-43.3 |
Dionysius |
01:45:07 |
-43.4 |
|
Aristarchus |
01:14:28 |
-33.0 |
Posidonius |
01:45:35 |
-33.3 |
|
Billy |
01:17:37 |
-47.0 |
Plinius |
01:45:57 |
-38.8 |
|
Kepler |
01:17:47 |
-38.8 |
Abulfeda |
01:46:40 |
-49.9 |
|
Pytheas |
01:24:32 |
-35.0 |
Bullialdus |
01:52:05 |
-53.1 |
|
Copernicus |
01:25:24 |
-38.9 |
Censorinus |
01:52:58 |
-45.4 |
|
Timocharis |
01:27:44 |
-33.2 |
Proclus |
01:55:09 |
-39.5 |
|
Pico |
01:29:45 |
-27.9 |
Taruntius |
01:57:21 |
-43.5 |
|
Plato |
01:29:53 |
-26.5 |
Nicolai |
01:57:34 |
-61.6 |
|
Campanus |
01:30:54 |
-53.6 |
Mare Crisium |
01:58:40 |
-39.5 |
|
Birt |
01:37:41 |
-52.3 |
Goclenius |
01:59:49 |
-49.8 |
|
Aristoteles |
01:38:18 |
-27.6 |
Langrenus |
02:04:45 |
-49.9 |
|
Eudoxus |
01:38:39 |
-29.1 |
Stevinus |
02:05:51 |
-59.1 |
|
Manilius |
01:39:10 |
-38.5 |
Limb (U2) |
02:11:12 |
-61.1 |
Emersions
|
Crater/Feature |
UTC |
Umbral Angle (°) |
Crater/Feature |
UTC |
Umbral Angle (°) |
|
Limb (U3) |
03:23:22 |
-25.5 |
Pico |
04:03:21 |
7.5 |
|
Riccioli |
03:31:01 |
-6.8 |
Plato |
04:04:02 |
8.9 |
|
Grimaldi |
03:31:18 |
-7.9 |
Manilius |
04:05:14 |
-3.1 |
|
Billy |
03:33:32 |
-11.6 |
Dionysius |
04:05:53 |
-8.0 |
|
Campanus |
03:37:13 |
-18.2 |
Menelaus |
04:08:36 |
-2.7 |
|
Tycho |
03:38:15 |
-24.8 |
Censorinus |
04:11:12 |
-10.0 |
|
Kepler |
03:43:23 |
-3.4 |
Plinius |
04:11:39 |
-3.4 |
|
Aristarchus |
03:44:52 |
2.4 |
Eudoxus |
04:11:39 |
6.3 |
|
Birt |
03:46:15 |
-16.8 |
Goclenius |
04:11:53 |
-14.4 |
|
Nicolai |
03:49:50 |
-26.1 |
Aristoteles |
04:12:00 |
7.8 |
|
Copernicus |
03:51:00 |
-3.5 |
Posidonius |
04:15:57 |
2.1 |
|
Pytheas |
03:53:38 |
0.4 |
Langrenus |
04:16:31 |
-14.5 |
|
Timocharis |
03:58:12 |
2.2 |
Taruntius |
04:17:44 |
-8.1 |
|
Abulfeda |
03:58:47 |
-14.5 |
Proclus |
04:20:02 |
-4.1 |
|
Bullialdus |
03:59:15 |
-17.7 |
Mare Crisium |
04:23:24 |
-4.1 |
|
Stevinus |
04:02:35 |
-23.7 |
Limb (U4) |
04:27:23 |
-1.0 |
ESTIMATING ECLIPSE BRIGHTNESS
The visual magnitude of the totally eclipsed
Moon has been seen to vary from almost invisibility +4.1 to -3.7,
that would rival Venus, and is mostly dependent on how deep it goes into
the umbra and also on global levels of volcanic aerosols in the stratosphere.
On April 22, 2015 there was a powerful explosion of Mount Calbuco
and observations made by the author of ash plumes that passed over Rio de
Janeiro four days later indicated that a small (though significant) fraction of
those aerosols had indeed reached the stratosphere. Thus a small but noticeable
decrease in the brightness of the eclipse is expected. If the stratosphere was
free of volcanic aerosols, we could use our empirical correlation, that relates
the predicted visual magnitude of the Moon (m) to the greatest magnitude of the
umbral eclipse (Umag) and also
to the apparent semidiameter of the Moon at greatest
eclipse (SD, expressed in arc minutes):
m = -1.9
+ 4.3 Umag - 5 log(SD) (Vital)
However, the eruption of Calbuco
may have darkened Earth`s umbra moderately. An educated guess would be to
assume a possible 1.3±0.8 magnitude decrease in the visual magnitude of the
Moon at mid-totality. In order to assist you in selecting comparison stars when
attempting to estimate the visual magnitude of the Moon, the following table lists
our predictions for the umbral eclipse magnitude and
the corresponding visual magnitude of the Moon as a function of time (UTC). Use
of the perfected reverse-binoculars method is recommended. An eclipse with prevailing color between deep
red and brick red coloration and of intermediate brightness is expected with
the northern half of the Moon`s disk
much darker than the southern.
PREDICTED UMBRAL MAGNITUDES AND VISUAL MAGNITUDES OF THE
MOON AS THE ECLIPSE DEVELOPS
|
Time (UTC) |
Eclipse Umbral Magnitude |
Visual Magnitude of the Moon |
Time (UTC) |
Eclipse Umbral Magnitude |
Visual Magnitude of the Moon |
|
01:07 |
0.00 |
-11.4 |
02:47 |
1.277 |
-1.2 |
|
01:13 |
0.10 |
-11.0 |
02:57 |
1.250 |
-1.4 |
|
01:19 |
0.20 |
-10.3 |
03:02 |
1.225 |
-1.6 |
|
01:25 |
0.30 |
-10.9 |
03:05 |
1.200 |
-1.8 |
|
01:28 |
0.35 |
-10.6 |
03:08 |
1.175 |
-2.1 |
|
01:31 |
0.40 |
-10.2 |
03:10 |
1.150 |
-2.3 |
|
01:34 |
0.45 |
-9.8 |
03:13 |
1.125 |
-2.5 |
|
01:37 |
0.50 |
-9.3 |
03:15 |
1.100 |
-2.7 |
|
01:40 |
0.55 |
-8.9 |
03:17 |
1.075 |
-2.9 |
|
01:44 |
0.60 |
-8.4 |
03:19 |
1.050 |
-3.1 |
|
01:47 |
0.65 |
-7.8 |
03:21 |
1.025 |
-3.3 |
|
01:50 |
0.70 |
-7.3 |
03:23 |
1.000 |
-3.5 |
|
01:53 |
0.75 |
-6.7 |
03:27 |
0.95 |
-4.2 |
|
01:57 |
0.80 |
-6.1 |
03:31 |
0.90 |
-4.8 |
|
02:00 |
0.85 |
-5.5 |
03:34 |
0.85 |
-5.5 |
|
02:04 |
0.90 |
-4.8 |
03:38 |
0.80 |
-6.1 |
|
02:07 |
0.95 |
-4.2 |
03:41 |
0.75 |
-6.7 |
|
02:11 |
1.000 |
-3.5 |
03:44 |
0.70 |
-7.3 |
|
02:13 |
1.025 |
-3.3 |
03:47 |
0.65 |
-7.8 |
|
02:15 |
1.050 |
-3.1 |
03:50 |
0.60 |
-8.4 |
|
02:17 |
1.075 |
-2.9 |
03:54 |
0.55 |
-8.9 |
|
02:19 |
1.100 |
-2.7 |
03:57 |
0.50 |
-9.3 |
|
02:21 |
1.125 |
-2.5 |
04:00 |
0.45 |
-9.8 |
|
02:24 |
1.150 |
-2.3 |
04:03 |
0.40 |
-10.2 |
|
02:26 |
1.175 |
-2.1 |
04:06 |
0.35 |
-10.6 |
|
02:29 |
1.200 |
-1.8 |
04:09 |
0.30 |
-10.9 |
|
02:33 |
1.225 |
-1.6 |
04:15 |
0.20 |
-10.3 |
|
02:37 |
1.250 |
-1.4 |
04:21 |
0.10 |
-11.0 |
|
02:47 |
1.277 |
-1.2 |
04:27 |
0.00 |
-11.4 |
Please, send us your contact timings and
visual magnitude estimates, briefly describing your observing conditions and
equipment. Danjon Number (L) estimates can be made
with basis on the color of the Moon at mid-eclipse and will also be welcomed. An
overall value of L=2.2±0.4 (1σ) at mid-eclipse would be our prediction. You
can use the Danjonmeter (a
color form) as a guide.
