Home > Ephemeris Program, Planets > 08/18/2021 – Ephemeris – Let’s search for the naked-eye planets for this week

08/18/2021 – Ephemeris – Let’s search for the naked-eye planets for this week

August 18, 2021

This is Bob Moler with Ephemeris for Wednesday, August 18th. Today the Sun will be up for 13 hours and 54 minutes, setting at 8:43, and it will rise tomorrow at 6:50. The Moon, 3 days past first quarter, will set at 3:02 tomorrow morning.

Let’s search for the naked-eye planets for this week. Venus should be visible in the western evening twilight by 9:15 tonight. It will set at 10:04 pm. By 9:30 pm, Jupiter and Saturn will be seen low in the southeastern sky. The brighter Jupiter will be easy to spot at that hour. Saturn will be dimmer, but a bit higher and to its right. Jupiter, just a day from opposition from the Sun, will be at its brightest and closest to us. It’s now 373 million miles (600 million km) from us. It won’t change much by tomorrow. Actually it’s a closer approach than average, so it’s brighter than at an average opposition and larger appearing than normal in telescopes. Jupiter and four of its largest moons always provide for a great show.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.


Venus in the west

Venus low in the west, tonight at 9:15, about a half hour after sunset, August 18, 2021. Created using Stellarium.

Jupiter, Saturn and the Moon at 10 pm

Jupiter, Saturn and the Moon at 10 pm, about an hour and a quarter after sunset tonight, August 18, 2021. Click on the image to enlarge it. Created using Stellarium.

The Moon as it might appear tonight

The waxing gibbous Moon as it might appear tonight in binoculars or a small telescope. Created using Stellarium.

The naked-eye planets as seen in small telescopes

Telescopic view of the bright planets (north up) as they would be seen in a small telescope, with the same magnification, this evening. Venus at 10 pm, and the other two at 11 pm, August 18, 2021. Apparent diameters: Venus, 13.93″; Saturn 18.51″, its rings 43.13″; Jupiter, 49.12″. Jupiter’s moon have a cluster of events in the am hours. See below. The ” symbol means seconds of arc (1/3600th of a degree.) Click on the image to enlarge it. Created using Cartes du Ciel (Sky Charts).

Satellite  Event             EDT (UT-4)   UT 
Europa     Shadow start      12:34 am     04:34
Europa	   Transit start     12:37 am     04:37
Io         Occultation start 12:37 am     04:37
Ganymede   Eclipse start     12:43 am     04:43
Io         Occultation end    2:55 am     06:55
Europa     Shadow end         3:25 am     07:25
Europa     Transit end        3:27 am     07:27
Ganymede   Occultation end    4:24 am     08:24

From 12:43 to 2:55 am, only Callisto of the four Galilean moons will be visible.

The above times were determined using Stellarium, and may be off by several minutes.
Shadow events are when a satellite’s shadow is cast onto the face of the planet
Transit events are when the satellite passes in front of the planet. The satellite is usually not visible
Eclipse events are when a satellite passes through the planet’s shadow
Occultation events are when the satellite passes behind the planet

Planets and the Moon overnight tonight

The naked-eye planets and the Moon are shown at sunset and sunrise of a single night, starting with sunset on the right on August 18, 2021. The night ends on the left with sunrise on the 19th. Mars and Mercury will be in conjunction in Leo that evening, so their labels overlap. Click on the image to enlarge. Created using my LookingUp program.

  1. August 22, 2021 at 2:43 am

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    • August 31, 2021 at 9:11 pm

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