Sky at Totality
The total phase of an eclipse is accompanied by the onset of
a rapidly darkening sky whose appearance resembles evening twilight
about 30 or 40 minutes after sunset. The effect presents an excellent
opportunity to view planets and bright stars in the daytime sky.
Aside from the sheer novelty of it, such observations are useful
in gauging the apparent sky brightness and transparency during
totality. The Sun is in Aquarius and a number of planets and bright
stars will be above the horizon for observers within the umbral
path.
Figure 8 depicts the appearance of the sky during totality
as seen from the center line at 1:00 UT. This corresponds to eastern
Russia near the northeast border of Mongolia. Venus is the brightest
planet and can actually be observed in broad daylight provided
that the sky is cloud free and of high transparency (i.e. - no
dust or particulates). During the 1997 eclipse, Venus is located
6° west of the Sun and is rapidly approaching superior conjunction
at month's end. Look for the planet during the partial phases
by first covering the crescent Sun with an extended hand. During
totality, it will be impossible to miss Venus since it shines
at a magnitude of mv=-3.4. Although two magnitudes fainter at
mv=-1.3, Mercury will also be well placed just 3° west of
the Sun. In fact, Mercury passes superior conjunction two days
after the eclipse. Together, Venus and Mercury should form a striking
pair during totality. Jupiter will be another prominent planet
located 38° west of the Sun and shining at mv=-1.5. Under
good conditions, it may be possible to spot Jupiter 5 to 10 minutes
before totality. Finally, Saturn is located 19° east of the
Sun at mv=+0.4, making it the most difficult planet to spot. Mars
is just past opposition and will be below the horizon during the
eclipse. A number of the brightest summer stars may also be visible
during totality. The summer triangle composed of Altair (mv=+0.77),
Deneb (mv=+1.25), and Vega (mv=+0.03), will be nearly overhead
to the south. Twenty degrees above the western horizon lies Arcturus
(mv=-0.04), while Capella (mv=+0.08) stands twelve degrees high
to the north northeast.
The following ephemeris [using Bretagnon and Simon, 1986] gives
the positions of the naked eye planets during the eclipse. Delta
is the distance of the planet from Earth (A.U.'s), V is
the apparent visual magnitude of the planet, and Elong
gives the solar elongation or angle between the Sun and planet.
Note that Mars is near opposition and will be below the horizon
for all observers during the eclipse.
Note: This is an HTML 3.0 table. The HTML 3.0 table directives
are currently (1995 August 1) supported by Netscape and Agena (at least),
but not by Mosaic (for example). A
text version of this table is also available for the
Web-viewer-challenged.
Planetary Ephemeris: 1997 Mar 9, 01:00 UT
Equinox = Mean Date
| Planet | RA | Dec | Delta | V | Size | Phase | Elong
|
|---|
| Sun | 23h17m42s | -04°32´53"
| 0.99290 | -26.7 | 1933.0
| |
|
| Mercury | 23h11m43s | -07°08´50"
| 1.36922 | -1.0 | 4.9
| 1.00 | 3.0W
|
| Venus | 22h57m00s | -08°14´21"
| 1.70648 | -3.4 | 9.8
| 0.99 | 6.3W
|
| Mars | 12h05m45s | +03°30´40"
| 0.67434 | -1.0 | 13.9
| 1.00 | 168.0W
|
| Jupiter | 20h52m27s | -18°01´41"
| 5.85974 | -1.5 | 33.6
| 1.00 | 38.0W
|
| Saturn | 00h31m09s | +00°58´27"
| 10.38375 | 0.4 | 15.9
| 1.00 | 19.2E
|
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