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Venus at dichotomy

Dominic Ford, Editor
From the Inner Planets feed

Objects: Venus
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The sky at

Venus will reach half phase in its 2015–2016 morning apparition. It will be shining brightly at mag -4.4.

From Fairfield , this apparition will be well placed and prominent, reaching a peak altitude of 41° above the horizon at sunrise on 14 Oct 2015.

Begin typing the name of a town near to you, and then select the town from the list of options which appear below.

The table below lists how high Venus will appear at sunrise over the course of the apparition. All times are given in Fairfield local time.

Date Sun
rises at
rises at
at sunrise
at sunrise
25 Aug 201506:1505:1511°east
04 Sep 201506:2504:2122°east
14 Sep 201506:3503:4531°east
24 Sep 201506:4503:2437°east
04 Oct 201506:5503:1540°south-east
14 Oct 201507:0603:1641°south-east
24 Oct 201507:1703:2241°south-east
03 Nov 201506:2902:3340°south-east
13 Nov 201506:4102:4739°south-east
23 Nov 201506:5303:0437°south-east
03 Dec 201507:0403:2234°south-east
13 Dec 201507:1203:4231°south-east
23 Dec 201507:1904:0327°south-east
02 Jan 201607:2104:2524°south-east
12 Jan 201607:2004:4521°south-east

A graph of the phase of Venus is available here.

Observing Venus

The 2015–2016 morning apparition of Venus
15 Aug 2015 – Venus at inferior solar conjunction
20 Sep 2015 – Venus at greatest brightness
24 Oct 2015 – Venus reaches highest point in morning sky
25 Oct 2015 – Venus at dichotomy
26 Oct 2015 – Venus at greatest elongation west

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 hours, 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 11h04m00s +05°51' Leo 24.4"
Sun 13h56m -11°55' Virgo 32'09"

The coordinates above are given in J2000.0.

The sky on 25 October 2015
Twilight ends
Twilight begins

12-day old moon
Waxing Gibbous


12 days old

Rise Culm. Set
Mercury 06:00 11:46 17:31
Venus 03:21 09:44 16:08
Moon 17:09 23:26 04:29
Mars 03:36 10:00 16:23
Jupiter 03:20 09:47 16:13
Saturn 09:52 14:44 19:37
All times shown in EDT.


The circumstances of this event were computed using the DE405 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

25 Oct 2015  –  Venus at dichotomy
26 Oct 2015  –  Venus at greatest elongation west
29 Nov 2015  –  Venus at perihelion
20 Mar 2016  –  Venus at aphelion

Image credit

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