Mercury at dichotomy

Dominic Ford, Editor
From the Inner Planets feed

Objects: Mercury
Please wait
Loading 0/4
Click and drag to rotate
Mouse wheel to zoom in/out
Touch with mouse to dismiss
The sky at

Mercury will reach half phase in its 2014 morning apparition. It will be shining brightly at mag -0.2.

From Fairfield , this apparition will not be one of the most prominent and tricky to observe, reaching a peak altitude of 14° above the horizon at sunrise on 15 Jul 2014.

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 Fairfield local time.

Date Sun
rises at
rises at
at sunrise
at sunrise
30 Jun 201405:2604:47east
03 Jul 201405:2804:34east
06 Jul 201405:2904:2410°east
09 Jul 201405:3104:1613°east
12 Jul 201405:3304:1113°east
15 Jul 201405:3604:0914°east
18 Jul 201405:3804:1014°east
21 Jul 201405:4004:1514°east
24 Jul 201405:4304:2412°east
27 Jul 201405:4604:3611°east
30 Jul 201405:4904:51east
02 Aug 201405:5205:09north-east

A graph of the phase of Mercury is available here.

Observing Mercury

The 2014 morning apparition of Mercury
12 Jul 2014 – Mercury at greatest elongation west
16 Jul 2014 – Mercury reaches highest point in morning sky
17 Jul 2014 – Mercury at dichotomy

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 06h18m10s +21°34' Gemini 7.1"
Sun 07h45m +21°14' Gemini 31'28"

The coordinates above are given in J2000.0.

The sky on 17 July 2014
Twilight ends
Twilight begins

20-day old moon
Waning Gibbous


20 days old

Rise Culm. Set
Mercury 04:08 11:33 18:58
Venus 03:37 11:06 18:36
Moon 23:44 05:21 11:33
Mars 13:20 18:45 00:13
Jupiter 06:02 13:21 20:41
Saturn 14:59 20:09 01:24
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

17 Jul 2014  –  Mercury at dichotomy
29 Jul 2014  –  Mercury at perihelion
08 Aug 2014  –  Mercury at superior solar conjunction
08 Sep 2014  –  Mercury reaches highest point in evening sky

Image credit







Color scheme