© NASA/JPL/MESSENGER

Mercury at dichotomy

Dominic Ford, Editor
From the Inner Planets feed

Objects: Mercury
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Mercury will reach half phase in its Mar–Apr 2026 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 9° above the horizon at sunrise on 25 Mar 2026.

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Mar–Apr 2026 morning apparition of Mercury

07 Mar 2026 – Mercury at inferior solar conjunction
27 Mar 2026 – Mercury at highest altitude in morning sky
03 Apr 2026 – Mercury at greatest elongation west
03 Apr 2026 – Mercury at dichotomy
14 May 2026 – Mercury at superior solar conjunction

The table below lists the altitude of Mercury at sunrise over the course of the apparition. All times are given in Cambridge local time.

Date Sun
rises at
Mercury
rises at
Altitude
at sunrise
Direction
at sunrise
Mag Phase
13 Mar 202606:5706:19east3.16%
16 Mar 202606:5206:06east2.113%
19 Mar 202606:4705:56east1.419%
22 Mar 202606:4205:48east0.926%
25 Mar 202606:3705:41east0.733%
28 Mar 202606:3105:36east0.538%
31 Mar 202606:2605:32east0.344%
03 Apr 202606:2105:28east0.249%
06 Apr 202606:1605:25east0.253%
09 Apr 202606:1105:22east0.158%
12 Apr 202606:0605:20east0.062%
15 Apr 202606:0105:18east-0.065%
18 Apr 202605:5605:16east-0.169%
21 Apr 202605:5105:14east-0.273%
24 Apr 202605:4705:13east-0.477%

Mercury will brighten rapidly at the start of its morning apparition as it emerges from inferior conjunction. Prior to its apparition, it passed between the Earth and Sun, at which time it had its unilluminated side turned towards the Earth and so appeared as a thin, barely illuminated crescent. As the apparition proceeds, this crescent waxes and becomes gibbous.

Since Mercury can only ever be observed in twilight, it is particularly difficult to find when it is in a thin crescent phase. Thus, it will be significantly easier to see in the days after it reaches its highest point in the sky – when it will show a gibbous phase – than in the days beforehand.

Altitude of Mercury at sunrise

A graph of the phase of Mercury is available here.

Apparitions of Mercury

29 Oct 2025 – Evening apparition
07 Dec 2025 – Morning apparition
19 Feb 2026 – Evening apparition
03 Apr 2026 – Morning apparition
15 Jun 2026 – Evening apparition
02 Aug 2026 – Morning apparition
12 Oct 2026 – 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 23h11m10s 7°05'S Aquarius 7.6"
Sun 00h50m 5°26'N Pisces 31'59"

The coordinates above are given in J2000.0.

The sky on 3 Apr 2026

The sky on 3 April 2026
Sunrise
06:21
Sunset
19:11
Twilight ends
20:49
Twilight begins
04:44

15-day old moon
Waning Gibbous

94%

15 days old

Planets
Rise Culm. Set
Mercury 05:30 11:06 16:43
Venus 07:14 14:05 20:56
Moon 20:12 01:29 06:37
Mars 05:47 11:39 17:31
Jupiter 11:28 19:03 02:37
Saturn 06:16 12:19 18:23
All times shown in EDT.

Source

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

03 Apr 2026  –  Mercury at greatest elongation west
10 Jun 2026  –  Mercury at highest altitude in evening sky
15 Jun 2026  –  Mercury at greatest elongation east
02 Aug 2026  –  Mercury at greatest elongation west

Image credit

© NASA/JPL/MESSENGER

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