© 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 1983 evening apparition. It will be shining brightly at mag -4.3.

From Ashburn , this apparition will be well placed and prominent, reaching a peak altitude of 36° above the horizon at sunset on 19 May 1983.

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1983 evening apparition of Venus

03 Nov 1982 – Venus at superior solar conjunction
09 May 1983 – Venus at highest altitude in evening sky
15 Jun 1983 – Venus at dichotomy
16 Jun 1983 – Venus at greatest elongation east
22 Jul 1983 – Venus at greatest brightness

A graph of the phase of Venus is available here.

Apparitions of Venus

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
21 Jan 1985 – Evening apparition
12 Jun 1985 – 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 08h49m30s 19°55'N Cancer 23.4"
Sun 05h33m +23°18' Taurus 31'29"

The coordinates above are given in J2000.0.

The sky on 25 January 2022
Twilight ends
Twilight begins

23-day old moon
Waning Crescent


23 days old

Rise Culm. Set
Mercury 06:49 11:56 17:03
Venus 05:27 10:35 15:44
Moon 00:18 05:59 11:31
Mars 05:13 09:52 14:32
Jupiter 08:51 14:20 19:48
Saturn 07:53 12:58 18:03
All times shown in EST.


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 May 1983  –  Venus at highest altitude in evening sky
16 Jun 1983  –  Venus at greatest elongation east
25 Oct 1983  –  Venus at highest altitude in morning sky
04 Nov 1983  –  Venus at greatest elongation west

Image credit

© NASA/Ricardo Nunes






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