Month: June 2018

2018, July: See Five Planets and Mars Opposition

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Look for 5 planets during the month.  From mid-northern latitudes, they are not visible simultaneously.  Look for Mercury about 30 minutes after sunset with binoculars, then wait for Mars to cross the southeastern horizon.  Four bright planets then span the sky from Mars to Venus.  Mars reaches its opposition later in the month.  The planet is closer than it’s been since 2003.

July opens with the waning gibbous moon in the south-southwest. Mars, now the second brightest planet, is 25° up in the south-southwest, 5.8° below the moon.  At the same time, Saturn is 10° up in the southwest.  With both planets near their oppositions, they appear in the southeastern sky during the evening and move westward during the night.  During the early evening, four bright planets are arched across the sky, with the trio of bright outer planets in retrograde.

One hour after sunset, brilliant Venus stands 14° up in the west.  Venus is 9° to the lower right of Regulus.  Watch Venus close in and pass Regulus during the first 9 days of the month.  At this hour, dimmer Mercury is 4° up in the west-northwest, setting nearly 90 minutes after sunset. Use binoculars to locate it. This speedy world approaches its greatest elongation during the first half of the month.

Meanwhile, bright Jupiter, 82° to the upper left of Venus, is 33° up in the south.  This giant planet is 2° west of Zubenelgenubi.  Saturn, just past its opposition and retrograding above the Teapot of Sagittarius, is 13° up in the southeast, 52° to the lower left of Jupiter.

Mars, racing toward its opposition later in the month, rises in the southeast 117 minutes after sunset.  The Red Planet, retrograding in Capricornus, appears 34° to the lower left of Saturn.  Start looking for the five naked eye planets during the early evening.  Look for Mercury during twilight, then wait for Mars to clear the southeast horizon. Here are the highlights for the first half of the month:

  • July 1: As the sky darkens, Venus is 9° to the lower right of Regulus.  Mars rises 117 minutes after sunset this evening.  The waning gibbous moon is 15° to the left of the planet.

  • July 2: The Venus-Mercury gap is 16.6°. Mercury sets 90 minutes after sunset, its maximum setting interval after sunset for this apparition. The Venus-Regulus gap is 8° this evening.  Watch Venus close the separation during the next several evenings: 07/03, 6.9°; 07/04, 5.7°; 07/05, 4.7°; 07/06, 3.6°; 07/07, 2.6°; 07/08, 1.5°.
  • July 4: The Venus-Mercury gap is 16.2°.  Mercury’s brightness is fading fast as it approaches its greatest elongation.  This evening its apparent magnitude is 0.2, but it is appearing in bright twilight.
  • July 6: The moon is at its Last Quarter phase at 2:51 a.m. CDT. Earth is at aphelion 94.5 million miles from the sun at 11:46 a.m. CDT.
    In early July, Venus passes the next signpost of the ecliptic, Regulus. This vivid blue star is less than one degree from Venus on July 9.


  • July 9: Venus is closest to Regulus this evening, 1 degree.  The planet appears to the upper right of the star.  Watch the gap widen during the next several evenings as Venus moves away and toward Spica. Venus has a conjunction with Regulus in about 13 months when they are near their solar conjunctions, both hiding in bright sunlight.  On October 3, 2020, Venus, 22° up in the morning sky at 90 minutes before sunrise, appears 33’ below the star.  On the previous morning, Venus is 36’ above Regulus.
  • July 12: Mercury is at its greatest elongation, 26.4° east of the sun at 12:29 a.m. CDT. Mercury is only 13° above the horizon at sunset. The Venus-Mercury gap is 16.4°.  Venus is now 3.4° past Regulus.  The gap grows about 1° each evening.  The moon is at its New phase, 9:48 p.m. CDT.
  • July 14: Not long after sunset look for the waxing crescent moon 2.1° to the left of Mercury with binoculars.  Mars passes 1.1° north of Psi Capricorni.
  • July 15: Venus passes 1° to the upper right of Rho Leonis.  The waxing crescent moon is between Venus and Regulus, 1.5° to the lower right of Venus and 5.1° to the upper left of Regulus.

At mid-month, Venus continues to dominate the evening sky with its brilliance.  At 65 minutes after sunset, Venus is 11° up in the west, setting about an hour later.  Venus is now 6.5° to the upper left of Regulus.  On July 15, the waxing crescent moon is 1.5° to the lower right of Venus. Mercury, now past greatest elongation and fading quickly into the sun’s glare, sets 71 minutes after sunset.  Use binoculars to catch it in bright twilight.  Jupiter, near Zubenelgenubi, is 30° up in the south-southwest.  Saturn, 19° up in the south-southeast, is 51° to the lower left of Jupiter.  Mars, the second brightest “star” and rising 65 minutes after sunset, is approaching its perihelic opposition. It is 18° up in the southwest 2 hours before sunrise.  Here are the highlights for the second half of the month:

July 16:  The waxing crescent moon is 11.9° to the upper left of Venus.  The Venus-Regulus gap is 7.7° and growing each day.

  • July 17: Jupiter’s retrograde ends 2° west of Zubenelgenubi.  Watch Jupiter move eastward toward the star during the next month. The waxing crescent moon is 24.8° to the upper left of Venus.  If you’ve not looked for all five naked eye planets, start looking for Mercury, 30 minutes after sunset with binoculars.
  • July 18: The waxing crescent moon is 9.2° to the upper right of Spica. During the next several nights, start looking for some Perseid meteors before the moon approaches its full phase, after midnight, and before morning twilight begins.
  • July 19: The moon is at its First Quarter phase, 2:52 p.m. CDT.  This evening the moon is 13.3° to the right of Jupiter.
  • July 20: Today is the 49th anniversary of Apollo 11’s historic moon landing. This date also marks the 42nd anniversary of the Viking 1 landing on Mars.  The waxing gibbous moon is 3.5° above Jupiter this evening.
  • July 22: The waxing gibbous moon is 8.4° above Antares.
  • July 24: This evening the waxing gibbous moon is 1.9° to the upper right of Saturn.

  • July 27: Mars (m=-2.8) is at opposition.  The Full Moon is 7° to the upper left of Mars.  The moon reaches its Full phase, 3:20 p.m. CDT.  Mercury (m=1.9) 32 minutes after sunset during early twilight.
  • July 31: Earth and Mars are closest (closest approach), 35.7 million miles away.

The month ends with four bright planets lined up across the early evening sky.  Brilliant Venus is 9° up in the west 70 minutes after sunset.  Mars is 7° up in the southeast.  Mars retrogrades until August 27.  It is 30° to the lower left of Saturn, 23° up in the south-southeast, above the Teapot of Sagittarius.  It retrogrades until September 6.  This ringed wonder is 49° to the left of Jupiter.  Jupiter is 26° up in the southwest, 1.5° to the right of Zubenelgenubi.  Watch this giant world narrow the gap to the star and pass it next month.  Jupiter is 50° to the left of Venus.


2018, June 1: #Mars Observations

From Astronomy Picture of the Day

From Robert C. Victor


This is dated material. Some of the events happen this week. Please share with others who may be interested. Thank you!

Skywatchers in midwestern U.S.,

On most of the last several mornings, I have taken my 6-inch Orion Dobsonian reflector outdoors during the couple of hours before sunrise, and used a 6-mm eyepiece (providing a magnification of 200-power) to observe Mars and Saturn. The south polar cap of Mars was immediately obvious!

The Martian southern hemisphere spring equinox occurred on May 22, so the polar cap is still near its maximum extent. I also noticed some dark markings on the disk, near the equator and southern latitudes, and a bright area near the following or morning (celestial east, Martian west) limb, which may have been morning frost or morning clouds. And at the northern limb, I noticed a very narrow bright area that could have been the edge of the northern polar hood of clouds. The north pole itself is tipped away from Earth by 15 degrees.

Keep in mind that as spring progresses in the Martian southern hemisphere, the southern polar cap will shrink rapidly, so if you wait until Mars becomes conveniently visible in the evening, a much smaller polar cap will remain. Opposition and closest approach of Mars will occur in the last week of July, but don’t wait until then!

In coming days, two of the most striking markings on Mars (in addition to the South Polar Cap) will be in excellent position as seen from the eastern U.S. in the hours before dawn, when Mars is highest in the southern sky.

The markings are (1) Syrtis Major, which displays a dark triangular shape resembling a northward-pointing India, centered just north of the Martian equator. Also at the same Martian longitude (290 degrees) is (2) Hellas Basin, which often appears very bright because of haze or surface frost deposit. Hellas is centered near lat. 42 degrees south and so appears between Syrtis Major and the South Polar Cap.

Currently, any particular Martian surface feature reaches the central meridian of Mars a little over 38 minutes later each day. So if you observe Mars at the same time each morning, a feature will first appear near the sunset terminator, near the celestial west limb of Mars where the solar illumination cuts off. (You’ll notice in early June that Mars appears not round, but in gibbous phase.) Each successive day at the same time, the Martian feature will move farther back from the sunset terminator, eventually passing near the center of the disk, and continuing on toward the morning (celestial western) limb. In each 24 hours, Mars makes less than one complete rotation.

Here are times (in CDT) when the longitude of the central meridian of Mars is equal to 290 degrees. At these times, Syrtis Major will appear a little north of the center of the Martian disk, and Hellas will appear well south of the disk center. Even if you observe up to three hours away from these times, the east-west foreshortening of these features will be less than 50 percent, but you’ll not want to observe too many hours before Mars reaches your local meridian — it’ll be too low for good seeing — or much after Mars crosses your local meridian, because you’d be viewing in the daytime.

Longitude of central meridian of Mars = 290 degrees;
Syrtis Major and Hellas transiting central meridian.

Tuesday      June  5   2:26 a.m. CDT
Wednesday June  6   3:04 a.m.
Thursday     June  7   3:43 a.m
Friday          June  8   4:21 a.m.
Saturday      June  9   4:59 a.m.
Sunday       June 10   5:38 a.m. (near sunrise, but observe earlier,
as these features approach the central meridian)

Monday    June 11   6:16 a.m.  ” ”
Tuesday   June 12   6:54 a.m.  ” ”


2018, June 1: Jupiter Shines From Southeast

Bright Jupiter, complimenting Venus in the western evening sky, shines from the south-southeastern sky this evening.  Now well past its opposition, Jupiter is passing Zubenelgenubi, in Libra.  Watch as Jupiter passes and moves away from the star.

For more about the bright evening planets, see these articles:

2018, June 1: Venus Gleams in West

Brilliant Venus shines from the western sky this evening. Tonight it reaches its maximum setting interval after sunset. — 2 hours, 40 minutes — for this evening appearance.  Watch Venus this month pass the Gemini Twins and move past the Beehive star cluster.

For more about the bright evening planets, see these articles: