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. The Sun is in Pisces and all five naked eye planets as well as a number of bright stars will be above the horizon for observers within the umbral path. Figure 17 depicts the appearance of the sky during totality as seen from the center line at 18:00 UT. This corresponds to northern Colombia near the northwest border of Venezuela.

Mercury (mv = -1.5) and Jupiter (mv = -1.9) are in close proximity to the eclipsed Sun and both will be easily visible during totality. As the brightest planet in the sky, Venus 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 1998 eclipse, Venus is located 42° west of the Sun where it will reach greatest elongation the following month. Look for the planet during the partial phases by first covering the crescent Sun with an extended hand. Venus will be shining at its greatest brilliancy (mv=-4.5) so it will be impossible to miss during totality. Mars (mv=+1.2) and Saturn (mv=+0.9) are located 17° and 40° east of the Sun, respectively. They will prove more challenging to spot than the other planets, but not too difficult if the sky transparency is good. Under the right circumstances, it should be possible to view all five classical planets, the Moon and the Sun (or at least it's corona) as one's eyes sweep across the darkened sky during totality.

A number of the brightest summer/autumn stars may also be visible during totality. Twenty degrees south of the Sun, Fomalhaut (mv=+1.16) will have an altitude of 50°, while Achernar (mv=+0.46) lies 20° above the southeastern horizon. The summer triangle composed of Altair (mv = +0.77), Deneb (mv = +1.25), and Vega (mv =+ 0.03), will be located in the northwest while Capella (mv = +0.08) stands 10° high in the 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: This is an HTML 3.0 table. The HTML 3.0 table directives are currently (1996 May 28) supported by Netscape and Internet Explorer (at least to some extent), but not by all Web viewers. A text-only version of this table is also available for the Web-viewer-challenged.

Planetary Ephemeris: 1998, February 26 18:00 UT
Equinox = Mean Date
Object	RA	Dec	Delta	V	Size	Phase	Elong
Sun	22h38m24s	-08°35´35"	0.99024	-26.7	1938.2
Mercury	22h55m01s	-08°37´19"	1.34548	-1.5	5.0	0.99	4.1E
Venus	19h47m35s	-15°56´33"	0.45918	-4.5	36.3	0.31	42.3W
Mars	23h44m19s	-02°30´47"	2.31165	1.2	4.0	0.99	17.5E
Jupiter	22h29m58s	-10°22´28"	5.99563	-1.9	32.8	1.00	2.7W
Saturn	01h09m22s	+04°52´23"	10.08826	0.9	16.4	1.00	40.0E

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