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Mercury at dichotomy

Dominic Ford, Editor
From the Inner Planets feed

Objects: Mercury
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Mercury will reach half phase in its 2024 morning apparition. It will be shining brightly at mag -0.5.

From Seattle , this apparition will be exceptionally well placed but tricky to observe, reaching a peak altitude of 16° above the horizon at sunrise on 6 Sep 2024.

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 Seattle local time.

Date Sun
rises at
rises at
at sunrise
at sunrise
25 Aug 202406:2005:37east
28 Aug 202406:2405:1710°east
31 Aug 202406:2805:0313°east
03 Sep 202406:3204:5615°east
06 Sep 202406:3604:5616°east
09 Sep 202406:4005:0215°east
12 Sep 202406:4405:1314°east
15 Sep 202406:4805:2812°east
18 Sep 202406:5205:4610°east
21 Sep 202406:5606:04east
24 Sep 202407:0006:23east

A graph of the phase of Mercury is available here.

Observing Mercury

The 2024 morning apparition of Mercury
18 Aug 2024 – Mercury at inferior solar conjunction
04 Sep 2024 – Mercury reaches highest point in morning sky
04 Sep 2024 – Mercury at greatest elongation west
05 Sep 2024 – 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 09h52m20s +13°12' Leo 7.0"
Sun 11h00m +06°23' Leo 31'44"

The coordinates above are given in J2000.0.

The sky on 05 September 2024
Twilight ends
Twilight begins

2-day old moon
Waxing Crescent


2 days old

Rise Culm. Set
Mercury 04:56 11:59 19:03
Venus 08:49 14:41 20:33
Moon 09:23 14:59 20:36
Mars 00:12 08:10 16:07
Jupiter 23:28 07:23 15:13
Saturn 19:48 01:22 06:52
All times shown in PDT.


Never attempt to point a pair of binoculars or a telescope at an object close to the Sun. Doing so may result in immediate and permanent blindness.


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

05 Sep 2024  –  Mercury at dichotomy
09 Sep 2024  –  Mercury at perihelion
30 Sep 2024  –  Mercury at superior solar conjunction
23 Oct 2024  –  Mercury at aphelion

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