© NASA/Ricardo Nunes

Venus at dichotomy

Dominic Ford, Editor
From the Inner Planets feed

Objects: Venus
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Venus will reach half phase in its 1981–1982 evening apparition. It will be shining brightly at mag -4.4.

From Cambridge , this apparition will not be one of the most prominent but , reaching a peak altitude of 23° above the horizon at sunset on 18 Dec 1981.

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1981–1982 evening apparition of Venus

07 Apr 1981 – Venus at superior solar conjunction
10 Nov 1981 – Venus at dichotomy
10 Nov 1981 – Venus at greatest elongation east
17 Dec 1981 – Venus at highest altitude in evening sky
19 Dec 1981 – Venus at greatest brightness
21 Jan 1982 – Venus at inferior solar conjunction

A graph of the phase of Venus is available here.

Apparitions of Venus

18 Jan 1979 – Morning apparition
04 Apr 1980 – Evening apparition
25 Aug 1980 – Morning apparition
10 Nov 1981 – Evening apparition
01 Apr 1982 – Morning apparition
16 Jun 1983 – Evening apparition
04 Nov 1983 – Morning apparition

Observing Venus

Venus's orbit lies closer to the Sun than the Earth's, meaning that it always appears close to the Sun and is lost in the Sun's glare much of the time.

It is observable for a few months each time it reaches greatest separation from the Sun – moments referred to as greatest elongation. These apparitions repeat roughly once every 1.6 years.

On these occasions, Venus is so bright and conspicuous that it becomes the third brightest object in the sky after the Sun and Moon. It is often called the morning star or the evening star.

Venus's phase

Venus's phase varies depending on its position relative to the Earth. When it passes between the Earth and Sun, for example, the side that is turned towards the Earth is entirely unilluminated, like a new moon.

Conversely, when it lies opposite to the Earth in its orbit, passing almost behind the Sun, it appears fully illuminated, like a full moon. However, at this time it is also at its most distant from the Earth, so it is actually fainter than at other times.

Venus shows an intermediate half phase – called dichotomy – at roughly the same moment that it appears furthest from the Sun, at greatest elongation. The exact times of the two events may differ by a few days, only because Venus's orbit is not quite perfectly aligned with the ecliptic.

Venus's position

The coordinates of Venus when it reaches dichotomy will be:

Object Right Ascension Declination Constellation Angular Size
Venus 18h23m00s 26°48'S Sagittarius 24.8"
Sun 15h02m 17°12'S Libra 32'18"

The coordinates above are given in J2000.0.

The sky on 28 Mar 2024

The sky on 28 March 2024
Sunrise
06:31
Sunset
19:05
Twilight ends
20:42
Twilight begins
04:55

18-day old moon
Waning Gibbous

86%

18 days old

Planets
Rise Culm. Set
Mercury 06:58 13:49 20:39
Venus 06:00 11:45 17:29
Moon 21:41 02:49 07:48
Mars 05:22 10:44 16:05
Jupiter 08:10 15:13 22:17
Saturn 05:45 11:17 16:50
All times shown in EDT.

Source

The circumstances of this event were computed using the DE430 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).

This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.

Related news

09 Sep 1980  –  Venus at highest altitude in morning sky
10 Nov 1981  –  Venus at greatest elongation east
18 Dec 1981  –  Venus at highest altitude in evening sky
01 Apr 1982  –  Venus at greatest elongation west

Image credit

© NASA/Ricardo Nunes

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42.38°N
71.11°W
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