Month: April 2018

2018, April 25: Venus and Sirius

Brilliant Venus shines from the west-northwest this evening.  It is now setting over 2 hours after sunset.  After you locate Venus look to the left along the horizon.  Sirius, the brightest star, is in the southwest, at about the same altitude (height above the horizon) as Venus. They will be at about the same altitude for the next several days. Compare their respective brightness: Venus the brightest planet and Sirius the brightest star.  Venus is about 10 times brighter than Sirius.

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


2018, April 10: The Morning Planets and the Moon

Less than a month before its opposition, Jupiter gleams from the southwest this morning. The planet is now rising in the east-southeast at about 10 p.m. Jupiter is retrograding near the star Zubenelgenubi.

Mars and Saturn are farther east, beyond the star Antares. Saturn rises before 2 a.m. with Mars following closely behind. Saturn’s opposition is in June. Mars’ opposition is July, three oppositions in 79 days.

This morning Mars and Saturn are about 4 degrees apart.  Saturn begins to retrograde in a week (April 17).

The waning crescent moon (24 days old) is low in the east-southeast this morning, outside the frame of the planets.

The articles that follow provide details about the planets visible without optical assistance (binoculars or telescope):

2018, April: Watch Venus Move Through Taurus

During late April, brilliant Venus moves through the stellar background of Taurus with its two bright star clusters:  Pleiades and Hyades.

On April 24, Venus is closest to Alcyone, the brightest star in the Pleiades cluster.  They are 3.5 degrees apart.

The Pleiades is a compact grouping of bright bluish stars known to school children as “The Seven Sisters.”  The cluster resembles a tiny dipper.  To the unaided eye, 6 or 7 stars are visible.  A dozen or so through binoculars.  A few hundred through telescopes.  The Hyades are nearby.  This group resembles a check mark, a letter “V” when Aldebaran is included, although it is not part of the cluster.

Astronomical theory describes that stars are formed in bunches from a stellar, gaseous nebula.  Over time the mutual gravitation pull of the stars within the cluster is not strong enough to keep the group together.  The Hyades and Pleaides are close enough (within 400 light years) that they can be seen without a telescope.  Many star clusters are just beyond the perception of our eyes.

The star cluster pair is best-observed through binoculars,  Start observing Venus’ movement through the region nightly at mid-month.  On April 18, the crescent moon appears among the Hyades.

Watch the events unfold during the spring evenings.

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

2018: May 8, Jupiter at Opposition


In mid-northern latitudes, May is one of the best months for sky watching.  While the sun continues to set later throughout the month amid warming temperatures, cool, clearing breezes blow from the northwest revealing a transparent sky.  Enjoy the season.

Jupiter is the first of the three bright outer planets to reach opposition in a span of 79 days.

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

Bright Jupiter enters the early evening sky at its opposition on May 8.  It is 3.2° from Zubenelgenubi.  Jupiter is retrograding and passes the star on June 3.  After the planet resumes direct motion, Jupiter passes the star again on August 15.   Jupiter ends the month, just 1° from Zubenelgenubi.  On the chart above, Jupiter gleams in the southeastern sky at 10:30 p.m. CDT on opposition night.

May opens with brilliant Jupiter shining in the west after sunset.


The waxing gibbous moon moon (16.1 days old) is 18° to the left of Jupiter.  The planet rises at 8:17 p.m. CDT (in Chicago), 18 minutes after sunset.

As the month ends, the moon passes into Jupiter’s field again.  The chart above shows the view in the south at 10:50 p.m. CDT.  Here are the highlights:

  • May 25: The waxing gibbous moon (10.7 days old) is 6.3°  above the star Spica.
  • May 26:  The waxing gibbous moon (11.6 days old) appears farther east this evening.  It is 9.3° to the right of Jupiter.
  • May 27:  The nearly full moon (12.6 days old), yet still waxing gibbous is 5.1°  to the left of Jupiter.
  • May 28:  The full moon is 17.5°  to the left of Jupiter and 10.9°  above Antares.

As the month closes Jupiter shines brightly in the southeast at sunset.

2018, Summer: Evening Planet Parade: Five Bright Planets Visible During One Evening

For about a month near the summer solstice, five planets are visible during the early evening, but they are not easily visible simultaneously from mid-northern latitudes.  As the sky darkens a parade of planets extends across the sky from brilliant Venus in the west to Mars in the southeast. The “X” factor of seeing 5 planets simultaneously is Mercury. It reaches its greatest elongation on July 12, although Mercury is visible throughout its apparition.

For more southerly locations in the United States and farther southern latitudes, see this article:  2018:  Five Planets Visible at Once

Here’s how to look for the five planets:

June 16, 2018:  Start looking for Mercury early it its apparition, although the rising time for Mars is much later.  From an observing location with a clear horizon, locate the speedy planet Mercury 30 minutes after sunset. Mercury sets 63 minutes after sunset, 15 minutes before Nautical Twilight (sun’s altitude is -12°).  Mars rises in a dark sky nearly 3 hours after sunset.  At 30 minutes after sunset on this evening, Venus is 25° to Mercury’s upper left.  The waxing crescent moon (3.3 days old) is 7.9° beyond Venus.

July 2:  Again with binoculars first locate Mercury 10° up in the west-northwest 30 minutes after sunset with brilliant Venus 16.6° to Mercury’s upper left.  Regulus is 8.1° beyond Venus.  Mars touches the east-southeast horizon 25 minutes after Mercury sets and 15 minutes before the end of twilight.

July 12: At sunset, Mercury is 13° up in the west-northwest.  Thirty minutes later, it has an altitude of only 8.5° with brilliant Venus 16.4° to its upper left.  Venus is 3.4° beyond Regulus.  Mercury sets 78 minutes after sunset and Mars touches the southeast horizon at the same time.  Locate Mercury, then wait until Mars clears the east-southeast horizon.

July 17: The best evenings for seeing all five planets are around this date, but you’ll need optical assistance.  Thirty minutes after sunset, dimmer Mercury is 5.1° above the horizon.  Mercury is dimmer as the apparition continues so optical aid is needed to first locate it. Regulus is 9.5° to the upper left of Mercury with Venus 8.5° beyond the star.  Mars rises six minutes before Mercury sets, although both are low in the sky.    Twilight lingers for over 2 hours at this time of the year at mid-northern latitudes.

On July 17, 2.5 hours after sunset and after Mercury sets, the planet parade arches across the southern sky.  Brilliant Venus sparkles 5° up in the west and Mars is 5° up in the southeast.  Saturn is 32.8° to the upper right of Mars, above the Teapot of Sagittarius.  Jupiter is 50.8° to the west of Saturn and 1.8° to the west of Zubenelgenubi.  The moon (5.0 days old) is nearly between Venus and Jupiter.

Another opportunity to see five planets simultaneously, from mid-northern latitudes, occurs in the morning near the time of the summer solstice in 2020.  While these groupings are infrequent, they provide magnificent displays of the solar system’s beauty.

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2018, April 2: Mars-Saturn Conjunction Morning

Mars passes 1.2 degrees below Saturn this morning.  Watch Mars move away from  Saturn during the next several days.  Saturn begins to retrograde on April 17, heading toward its opposition in  June.




On the larger scale, Jupiter is in the southwest.  A bright waning gibbous moon (just outside the frame beyond Jupiter) illuminates the scene.

The articles that follow provide details about the planets visible without optical assistance (binoculars or telescope):