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 to 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.

During the total solar eclipse of 2001, the Sun is in Gemini. Depending on the geographic location, three or four naked eye planets as well as a number of bright stars will be above the horizon within the umbral path. Figure 15 depicts the appearance of the sky during totality as seen from the center line at 13:00 UT. This corresponds to western Zambia near the Angolan border.

The most conspicuous planet visible will be Jupiter (m_v=-1.5) just 5° west of the Sun. Although Mercury (m_v=+2.7) is 8.6° west of the Sun, it is quite faint and will be difficult to spot. With a modest phase of 0.03, Mercury's illuminated face points away from Earth since the planet passed through inferior conjunction just five days earlier. Saturn (m_v=+0.3) should prove an easier target 22.6° west of the Sun. Venus (m_v=-3.3) is brightest of all, but the planet is near its greatest elongation 45.3° west of the Sun. Venus will be low in the west for observers in Angola and western Zambia. East of those positions, the planet will have already set before totality begins. Mars is near opposition and is below the horizon for all points along the entire umbral path.

A number of the brightest winter stars may also be visible during totality. Capella (m_v=+0.08) is 24° north of the Sun while Castor (m_v=+1.94) and Pollux (m_v=+1.14) stand 22° and 24° to the east. Procyon (m_v=+0.38) and Sirius (m_v=-1.46) are located 30° and 42° to the southeast, respectively. Betelgeuse (m_v=+0.5v) and Rigel (m_v=+0.12) are south at 16° and 34°, while Aldebaran (m_v=+0.85) is 21° to the west. Finally, Canopus (m_v=-0.72) lies high in the sky 76° due south. Star visibility requires a very dark and cloud free sky during totality.

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), App. Mag. is the apparent visual magnitude of the planet, and Solar Elong gives the elongation or angle between the Sun and planet.

Planetary Ephemeris: 2001 June 21 13:00:00 UT
Equinox = Mean Date
Object	RA	Dec	Delta	V	Apparent Diameter (")	Phase	Solar Elong (°)
Sun	06h00m56s	+23°26´19"	1.01628	-26.7	1888.6
Moon	06h03m27s	+22°55´26"	0.00245	12.2	1955.9	0.00	0.8E
Mercury	05h29m52s	+18°53´11"	0.57273	2.7	11.7	0.03	8.6W
Venus	02h53m30s	+13°40´18"	0.80823	-3.8	20.6	0.56	45.3W
Mars	17h16m20s	-26°44´01"	0.45018	-2.1	20.8	1.00	169.4E
Jupiter	05h38m52s	+23°02´33"	6.11294	-1.5	32.2	1.00	5.1W
Saturn	04h25m15s	+19°56´56"	10.01774	0.3	16.6	1.00	22.5W

For sky maps from other locations along the path of totality, see the special web site for the total solar eclipse of 2001.

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