Mercury at dichotomy

Dominic Ford, Editor
From the Inner Planets feed

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

From Cambridge , this apparition will not be one of the most prominent and very difficult to observe, reaching a peak altitude of 10° above the horizon at sunrise on 5 Mar 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 Cambridge local time.

Date Sun
sets at
rises at
at sunrise
at sunrise
21 Feb 201406:3505:51west
24 Feb 201406:3005:36west
27 Feb 201406:2505:24west
02 Mar 201406:2105:1510°west
05 Mar 201406:1605:0910°west
08 Mar 201406:1105:0410°west
11 Mar 201407:0406:0010°west
14 Mar 201406:5905:58west
17 Mar 201406:5405:56west
20 Mar 201406:4805:55west
23 Mar 201406:4305:54west
26 Mar 201406:3805:53west
29 Mar 201406:3305:52west
01 Apr 201406:2805:51west

A graph of the phase of Mercury is available here.

Observing Mercury

The 2014 morning apparition of Mercury
15 Feb 2014 – Mercury at inferior solar conjunction
03 Mar 2014 – Mercury reaches highest point in morning sky
11 Mar 2014 – Mercury at dichotomy
14 Mar 2014 – Mercury at greatest elongation west

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 days 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 21h41m50s -14°07' Capricornus 7.6"
Sun 23h24m -03°48' Aquarius 32'12"

The coordinates above are given in J2000.0.

The sky on 11 March 2014
Twilight ends
Twilight begins

10-day old moon
Waxing Gibbous


10 days old

Rise Culm. Set
Mercury 06:00 11:10 16:21
Venus 04:50 09:52 14:55
Moon 14:26 21:27 03:51
Mars 21:32 03:12 08:47
Jupiter 12:34 20:11 03:51
Saturn 23:48 04:53 09:55
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 Mar 2014  –  Mercury reaches highest point in morning sky
14 Mar 2014  –  Mercury at greatest elongation west
22 May 2014  –  Mercury reaches highest point in evening sky
25 May 2014  –  Mercury at greatest elongation east

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