Mercury at dichotomy

Dominic Ford, Editor
From the Inner Planets feed

Objects: Mercury
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The sky at

Mercury will reach half phase in its 2019 morning apparition. It will be shining brightly at mag 0.2.

From Washington , this apparition will not be one of the most prominent and very difficult to observe, reaching a peak altitude of 11° above the horizon at sunrise on 8 Apr 2019.

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 Mercury will appear at sunrise over the course of the apparition. All times are given in Washington local time.

Date Sun
rises at
rises at
at sunrise
at sunrise
18 Mar 201907:4207:11east
21 Mar 201907:3806:56east
24 Mar 201907:3306:44east
27 Mar 201907:2906:3410°east
30 Mar 201907:2406:2610°east
02 Apr 201907:2006:2011°east
05 Apr 201907:1506:1511°east
08 Apr 201907:1106:1111°east
11 Apr 201907:0706:0711°east
14 Apr 201907:0306:0511°east
17 Apr 201906:5906:0210°east
20 Apr 201906:5506:0110°east
23 Apr 201906:5105:5910°east
26 Apr 201906:4705:59east
29 Apr 201906:4305:58east
02 May 201906:4005:58east
05 May 201906:3705:59east
08 May 201906:3406:01east

A graph of the phase of Mercury is available here.

Observing Mercury

The 2019 morning apparition of Mercury
14 Mar 2019 – Mercury at inferior solar conjunction
10 Apr 2019 – Mercury reaches highest point in morning sky
11 Apr 2019 – Mercury at greatest elongation west
12 Apr 2019 – Mercury at dichotomy
21 May 2019 – Mercury at superior solar conjunction

Mercury'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 only a few weeks each time it reaches greatest separation from the Sun – moments referred to as greatest elongation. These apparitions repeat roughly once every 3–4 months.

Mercury's phase

Mercury'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.

Mercury 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 Mercury's orbit is not quite perfectly aligned with the ecliptic.

Mercury's position

The coordinates of Mercury when it reaches dichotomy will be:

Object Right Ascension Declination Constellation Angular Size
Mercury 23h45m00s -04°00' Aquarius 7.6"
Sun 01h23m +08°47' Pisces 31'54"

The coordinates above are given in J2000.0.

The sky on 12 April 2019
Twilight ends
Twilight begins

7-day old moon
Waxing Gibbous


7 days old

Rise Culm. Set
Mercury 06:06 11:56 17:46
Venus 05:51 11:38 17:25
Moon 12:52 20:04 02:21
Mars 09:19 16:36 23:53
Jupiter 00:58 05:47 10:37
Saturn 02:46 07:39 12:33
All times shown in MDT.


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

12 Apr 2019  –  Mercury at dichotomy
21 May 2019  –  Mercury at superior solar conjunction
24 May 2019  –  Mercury at perihelion
17 Jun 2019  –  Mercury reaches highest point in evening sky

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