Mercury will reach half phase in its 2016 evening apparition. It will be shining brightly at mag -0.4.
From Fairfield , this apparition will not be one of the most prominent and very difficult to observe, reaching a peak altitude of 11° above the horizon at sunset on 14 Dec 2016.
The table below lists how high Mercury will appear at sunset over the course of the apparition. All times are given in Fairfield local time.
| Date | Sun sets at |
Mercury sets at |
Altitude at sunset |
Direction at sunset |
| 20 Nov 2016 | 16:29 | 17:07 | 5° | south-west |
| 23 Nov 2016 | 16:28 | 17:12 | 6° | south-west |
| 26 Nov 2016 | 16:26 | 17:17 | 7° | south-west |
| 29 Nov 2016 | 16:25 | 17:23 | 8° | south-west |
| 02 Dec 2016 | 16:24 | 17:29 | 9° | south-west |
| 05 Dec 2016 | 16:24 | 17:35 | 10° | south-west |
| 08 Dec 2016 | 16:24 | 17:41 | 10° | south-west |
| 11 Dec 2016 | 16:24 | 17:46 | 11° | south-west |
| 14 Dec 2016 | 16:24 | 17:48 | 11° | south-west |
| 17 Dec 2016 | 16:25 | 17:45 | 11° | south-west |
| 20 Dec 2016 | 16:26 | 17:37 | 10° | south-west |
| 23 Dec 2016 | 16:28 | 17:20 | 8° | south-west |
A graph of the phase of Mercury is available here.
Observing Mercury
| 11 Dec 2016 | – Mercury at greatest elongation east |
| 14 Dec 2016 | – Mercury at dichotomy |
| 16 Dec 2016 | – Mercury reaches highest point in evening sky |
| 05 Jun 2016 | – Mercury at greatest elongation west |
| 16 Aug 2016 | – Mercury at greatest elongation east |
| 28 Sep 2016 | – Mercury at greatest elongation west |
| 11 Dec 2016 | – Mercury at greatest elongation east |
| 19 Jan 2017 | – Mercury at greatest elongation west |
| 01 Apr 2017 | – Mercury at greatest elongation east |
| 17 May 2017 | – 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 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 | 18h57m30s | -24°16' | Sagittarius | 7.3" |
| Sun | 17h29m | -23°14' | Ophiuchus | 32'29" |
The coordinates above are given in J2000.0.
| The sky on 14 December 2016 | ||||||||||||||||||||||||||||||||||
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99% 15 days old |
All times shown in EST.
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Source
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
| 14 Dec 2016 | – Mercury at dichotomy |
| 16 Dec 2016 | – Mercury reaches highest point in evening sky |
| 25 Dec 2016 | – Mercury at perihelion |
| 28 Dec 2016 | – Mercury at inferior solar conjunction |
Image credit
None available.