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 Jun–Jul 2002 morning apparition. It will be shining brightly at mag -0.1.

From Ashburn , this apparition will not be one of the most prominent and tricky to observe, reaching a peak altitude of 13° above the horizon at sunrise on 27 Jun 2002.

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

Jun–Jul 2002 morning apparition of Mercury

27 May 2002 – Mercury at inferior solar conjunction
21 Jun 2002 – Mercury at greatest elongation west
26 Jun 2002 – Mercury at highest altitude in morning sky
27 Jun 2002 – Mercury at dichotomy
20 Jul 2002 – Mercury at superior solar conjunction

A graph of the phase of Mercury is available here.

Apparitions of Mercury

11 Jan 2002 – Evening apparition
21 Feb 2002 – Morning apparition
03 May 2002 – Evening apparition
21 Jun 2002 – Morning apparition
31 Aug 2002 – Evening apparition
13 Oct 2002 – Morning apparition
26 Dec 2002 – Evening apparition

Observing Mercury

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 days, 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 04h50m50s 19°56'N Taurus 7.1"
Sun 06h23m +23°19' Gemini 31'28"

The coordinates above are given in J2000.0.

The sky on 25 January 2022
Twilight ends
Twilight begins

23-day old moon
Waning Crescent


23 days old

Rise Culm. Set
Mercury 06:49 11:56 17:03
Venus 05:27 10:35 15:44
Moon 00:18 05:59 11:31
Mars 05:13 09:52 14:32
Jupiter 08:51 14:20 19:48
Saturn 07:53 12:58 18:03
All times shown in EST.


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

26 Jun 2002  –  Mercury at highest altitude in morning sky
22 Aug 2002  –  Mercury at highest altitude in evening sky
31 Aug 2002  –  Mercury at greatest elongation east
13 Oct 2002  –  Mercury at greatest elongation west

Image credit







Color scheme