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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 2017 morning apparition. It will be shining brightly at mag -4.3.

From Fairfield , this apparition will not be one of the most prominent but prominent, reaching a peak altitude of 31° above the horizon at sunrise on 9 Aug 2017.

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
sets at
rises at
at sunrise
at sunrise
01 May 201705:5204:0918°north-west
11 May 201705:4103:5119°north-west
21 May 201705:3203:3521°north-west
31 May 201705:2503:2022°north-west
10 Jun 201705:2303:0824°north-west
20 Jun 201705:2302:5726°north-west
30 Jun 201705:2602:4928°north-west
10 Jul 201705:3302:4429°north-west
20 Jul 201705:4102:4431°north-west
30 Jul 201705:5002:4931°north-west
09 Aug 201705:5902:5931°north-west
19 Aug 201706:0903:1330°north-west
29 Aug 201706:1903:3229°north-west
08 Sep 201706:2903:5328°north-west
18 Sep 201706:3904:1526°north-west
28 Sep 201706:4904:3823°west
08 Oct 201707:0005:0121°west
18 Oct 201707:1105:2418°west

A graph of the phase of Venus is available here.

Observing Venus

The 2017 morning apparition of Venus
25 Mar 2017 – Venus at inferior solar conjunction
26 Apr 2017 – Venus at greatest brightness
03 Jun 2017 – Venus at greatest elongation west
04 Jun 2017 – Venus at dichotomy
30 Jul 2017 – Venus reaches highest point in morning sky

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 01h46m20s +08°31' Pisces 23.6"
Sun 04h48m +22°25' Taurus 31'31"

The coordinates above are given in J2000.0.

The sky on 04 June 2017
Twilight ends
Twilight begins

10-day old moon
Waxing Gibbous


10 days old

Rise Culm. Set
Mercury 04:29 11:36 18:43
Venus 03:15 09:49 16:22
Moon 15:55 21:38 02:53
Mars 06:23 13:59 21:36
Jupiter 15:00 20:49 02:43
Saturn 20:56 01:41 06:22
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

04 Jun 2017  –  Venus at dichotomy
12 Jun 2017  –  Venus at aphelion
30 Jul 2017  –  Venus reaches highest point in morning sky
03 Oct 2017  –  Venus at perihelion

Image credit

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