© NASA/Ricardo Nunes

Venus at greatest elongation east

Dominic Ford, Editor
From the Inner Planets feed

Objects: Venus
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Venus will reach its greatest separation from the Sun in its 2013–2014 evening apparition. It will be shining brightly at mag -4.4.

From Ashburn , this apparition will not be one of the most prominent, reaching a peak altitude of 22° above the horizon at sunset on 8 Dec 2013.

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2013–2014 evening apparition of Venus

28 Mar 2013 – Venus at superior solar conjunction
30 Oct 2013 – Venus at dichotomy
31 Oct 2013 – Venus at greatest elongation east
07 Dec 2013 – Venus at highest altitude in evening sky
09 Dec 2013 – Venus at greatest brightness
11 Jan 2014 – Venus at inferior solar conjunction

The table below lists the altitude of Venus at sunset over the course of the apparition. All times are given in Ashburn local time.

Date Sun
sets at
sets at
at sunset
at sunset
Mag Phase
08 Sep 201319:3221:0416°south-west-4.171%
18 Sep 201319:1620:5116°south-west-4.168%
28 Sep 201319:0020:4116°south-west-4.264%
08 Oct 201318:4520:3516°south-west-4.260%
18 Oct 201318:3120:3016°south-west-4.356%
28 Oct 201318:1520:3217°south-west-4.451%
07 Nov 201317:0619:3519°south-west-4.546%
17 Nov 201316:5519:3920°south-west-4.540%
27 Nov 201316:5119:3821°south-west-4.634%
07 Dec 201316:5019:3422°south-west-4.726%
17 Dec 201316:5019:1821°south-west-4.617%
27 Dec 201316:5518:4517°south-west-4.58%
06 Jan 201417:0317:50south-west-4.21%

Altitude of Venus at sunset

A graph of the angular separation of Venus from the Sun around the time of greatest elongation is available here.

Apparitions of Venus

08 Jan 2011 – Morning apparition
26 Mar 2012 – Evening apparition
15 Aug 2012 – Morning apparition
31 Oct 2013 – Evening apparition
23 Mar 2014 – Morning apparition
06 Jun 2015 – Evening apparition
26 Oct 2015 – Morning apparition

Observing Venus

Venus's orbit lies closer to the Sun than the Earth's, meaning 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.

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.

These apparitions repeat roughly once every 1.6 years, taking place alternately in the morning and evening skies, depending whether Venus lies to the east of the Sun or to the west.

When it lies to the east, it rises and sets a short time after the Sun and is visible in early evening twilight. When it lies to the west of the Sun, it rises and sets a short time before the Sun and is visible shortly before sunrise.

At each apparition, Venus reaches a maximum separation from the Sun of around 48°. However, some times of the year are more favourable for viewing Venus than others. From Ashburn, it reaches a peak altitude of between 19° and 46° above the horizon at sunset during each evening apparition, depending on the time of year. During its 2013–2014 apparition, it will peak at 22° above the horizon at sunset on 8 Dec 2013.

This variability over the course of the year is due to the inclination of the ecliptic to the horizon.

The inclination of the ecliptic to the horizon

The inclination of the ecliptic to the horizon changes over the course of the year, affecting how high planets close to the Sun appear in the sky.

At all times, Venus lies close to a line across the sky called the ecliptic, which is shown in yellow in the planetarium above. This line traces the path that the Sun takes through the zodiacal constellations every year, and shows the plane of the Earth's orbit around the Sun. Since all the planets circle the Sun in almost exactly the same plane, it also closely follows the planes of the orbits of the other planets, too.

When Venus is widely separated from the Sun, it is separated from it along the line of the ecliptic. But, at different times of year, the ecliptic meets the horizon at different angles at sunset. This means that Venus appears at different altitudes above the horizon at different times of year, even if its separation from the Sun is the same.

If the ecliptic meets the horizon at a shallow angle, then Venus has to be very widely separated from the Sun to appear much above the horizon. Conversely, if the ecliptic is almost perpendicular to the horizon, Venus may appear much higher in the sky, even if it is actually much closer to the Sun.

At sunset, the ecliptic makes its steepest angle to the horizon at the spring equinox – in March in the northern hemisphere, and in September in the southern hemisphere. Conversely, it meets the horizon at its shallowest angle at the autumn equinox. Because the seasons are opposite in the northern and southern hemispheres, a good apparition of Venus in one hemisphere will usually be poorly placed in the other.

At sunrise, these dates are also inverted, so that for morning apparitions of Venus, the ecliptic makes its steepest angle to the horizon at the autumn equinox, and its shallowest angle to the horizon at the spring equinox.

The optimum time for an apparition of Venus

The maximum altitude of Venus during all its evening apparitions between 2000 and 2050, as a function of the day of the year on which greatest western elongation occurs. Different colours show the altitudes observed from different latitudes. Click to expand.

For this reason, the day when Venus reaches its widest separation from the Sun (greatest elongation) is not necessarily the same day when it appears highest in the sky at sunset. Venus typically appears highest in the sky a few days or weeks closer to the spring equinox than the moment of greatest elongation.

The inclination of the ecliptic plane to the horizon at Ashburn varies between 74° (sunset at the spring equinox) and 27° (sunset at the autumn equinox). On October 31, the ecliptic is inclined at 30° to the western sunset horizon, as shown by the yellow line in the planetarium above, meaning that this apparition of Venus will not be one of the most prominent, reaching a peak altitude of 22° above the horizon at sunset.

Venus's position

The position of Venus when it reaches greatest elongation will be:

Object Right Ascension Declination Constellation Magnitude Angular Size
Venus 17h40m20s 26°59'S Ophiuchus -4.4 25.0"
Sun 14h25m -14°23' Libra -26.7 32'13"

The coordinates above are given in J2000.0.

The sky on 31 October 2013
Twilight ends
Twilight begins

26-day old moon
Waning Crescent


26 days old

Rise Culm. Set
Mercury 07:56 13:05 18:14
Venus 11:42 16:08 20:34
Moon 04:23 10:31 16:28
Mars 02:45 09:19 15:54
Jupiter 22:39 05:59 13:18
Saturn 07:59 13:16 18:33
All times shown in EDT.


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

31 Oct 2013  –  Venus at greatest elongation east
08 Dec 2013  –  Venus at highest altitude in evening sky
15 Feb 2014  –  Venus at highest altitude in morning sky
23 Mar 2014  –  Venus at greatest elongation west

Image credit

© NASA/Ricardo Nunes






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