July 2021: Elusive Mercury appears in the morning sky in the east-northeast during morning twilight. The best mornings to see Mercury are July 7 and July 8, when the moon is nearby.
by Jeffrey L. Hunt
Mercury puts on a morning display during July, reaching its greatest separation from the sun on July 4.
The planet started its appearance during mid-June, but it was dim. With the longer twilight period, the planet appears in a brighter sky. A dim planet and a brighter sky make for difficult observing of the planet.
By July 1, Mercury rises 71 minutes before sunrise and it is brightening each morning. The planet is less than 4° in altitude in the east-northeast about 45 minutes before sunrise.
Mercury joins bright Jupiter and Saturn in the morning sky as three of the five bright planets that are visible to the unaided eye.
Likely the best view of the speedy planet is on the mornings of July 7 and July 8 when the moon is nearby.
On the photo above, notice the thin moon to the left of Mercury.
Here’s how to see Mercury and the moon:
Find a clear horizon to the east-northeast, free from trees or other structures. A hilltop or elevated structure helps with the view over any obstructions. A binocular assists in the initial observation of the moon and Mercury.
Leading up to July 7, follow the moon’s morning progression through the eastern sky.
July 7: Forty-five minutes before sunrise, use a binocular to locate the crescent moon that is over 10° up in the east-northeast. The lunar crescent is only 6% illuminated. Mercury is 8.2° to the lower left of the lunar slice.
Mercury is just outside the field of view of a binocular. In the binocular field, put the moon to the upper right portion of the circular view. Then move the binocular slightly to the lower left. Mercury will move into the field of view. Can you see the planet without the binocular’s optical assist?
July 8: Again, this morning, 45 minutes before sunrise, the moon is lower in the sky and displays a thinner crescent, 2% illuminated, than yesterday. At this hour the moon is about 6° up in the east-northeastern sky. Mercury is 4.4° to the right of the thin moon. Both fit into a binocular’s field of view. Are both visible to the unaided eye?
After the moon moves away, the planet is about 5° above the horizon for the next several mornings. It is brighter each morning. The chart above shows the planet on July 15 when it rises 80 minutes before sunrise. After about midmonth, the planet is lower in the sky at 45 minutes before sunrise.
Begin looking later (30 minutes before sunrise). What is the last date you can find the planet with a binocular?
Mercury quickly speeds out of view and passes behind the sun on August 1 and moves into the evening sky.
On August 18, Mercury passes Mars in a challenging-to-observe close conjunction. On this evening all five bright planets are in the sky at the same time, but this occurs early during evening twilight.
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