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2021, July: Mercury’s Summer Morning Visibility

The crescent moon before sunrise, July 19, 2020.

2020, July 19: The crescent moon

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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.

Photo Caption: 2020, July 19: Mercury appears 5.0° to the right of the crescent moon.

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.

Chart Caption – 2021, July 7: Forty-five minutes before sunrise, the thin crescent moon is 8.2° to the upper right of Mercury.

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?

Chart Caption – 2021, July 8: Forty-five minutes before sunrise, the crescent moon is 4.4° to the left of Mercury.

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?

Chart Caption – 2021, July 15: Mercury is about 5° above the east-northeast horizon.

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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2021, October 25:  Caught Between the Horns

October 25, 2021: This morning the bright gibbous moon seems to be caught between the horns of Taurus.  Mercury is making its best morning appearance.  The planet pack – Venus, Jupiter, and Saturn are in the evening sky.

2021, October 24: Saturn Inches Toward Jupiter

October 24, 2021:  Saturn is at its closest to Jupiter as the Jovian Giant picks up eastward speed.  The morning moon and Mercury are visible before sunrise.  Brilliant Evening Star Venus, Saturn, and Jupiter are in the sky after sunset.

2021, October 23: Morning Moon Near Pleiades

October 23, 2021:  This morning the bright moon is near the Pleiades star cluster.  Mercury is making its best morning appearance.  In the evening sky, Venus, Jupiter and Saturn are easy to spot.

2021, October 22, Mercury’s Morning Best, Arcturus

October 22. 2021:  Speedy Mercury is low in the east before sunrise.  It is putting on its best morning performance of the year.  Arcturus, in the east-northeast, is about the same altitude as Mercury.

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