Moon’s movements
Our August evenings start with a crescent moon setting and Mercury below it in Leo. The messenger planet is hard to see at first from the northern hemisphere. But keep looking night to night and it’ll show up. On the opposite side of the sky, Saturn’s rising in Capricornus. The waxing moon moves through Virgo from the 1st through the 4th. During that time Mercury passes Regulus.
The first quarter moon moves through Libra on the 5th. It’s in the head of Scorpius the next night. Many of us at mid-northern latitudes get our best view of the constellation this time of year right as darkness begins. After passing south of Ophiuchus on the 7th, the moon’s in Sagittarius on the 8th and 9th.
On the 10th, a waxing gibbous moon is on the western side of Capricornus. It’ll join Saturn on the eastern side the next night and become full on the 12th in Aquarius. By that time, back on the western side of the evening sky, Mercury’s beneath the belly of Leo. It’s still a challenge for northern hemisphere viewers. With more than two week until greatest elongation, just keep trying.
Jupiter is visited by a waning gibbous moon on the evening of the 14th to morning of the 15th. The big planet is alongside the southern fish in Pisces. The moon is almost at last quarter as it passes by Uranus on the morning of the 18th. Last quarter is the next day when the moon passes by Mars. You’ll see the red planet close on the south side and the Pleiades on the north. The moon wanes to a crescent and goes west of the Hyades V on the 20th.
A thinner crescent passes by the star Elnath on the 21st. From the 22nd through 24th, the moon passes through Gemini. Both twins are easily visible on late August mornings with Orion completely visible too to the south of them.
This month’s Venus-moon close call is on the 25th. The moon is You can try to find the very thin crescent moon below Venus on the 26th as it heads into the morning light.
After new moon on the 27th, the moon is a waxing crescent again on the evening of the 28th. It’s right of Mercury one day past its greatest elongation. This may be the best chance for northern hemisphere sky watcher to positively identify the messenger planet. The thickening crescent moon moves through Virgo the remaining evenings of the month.
Moon circumstances
The moon goes south over the equator on the 2nd. Southern lunistice is on the 9th at 27.0°. The moon crosses the equator going north on the 15th. Northern lunistice is on the 22nd at 27.1°. The moon crosses the equator southward again on the 29th.
First quarter is on the 5th at 11:07 UT. Full moon is on the 12th at 01:36. Last quarter is on the 19th at 04:37. And new moon is on the 27th at 08:18.
Perigee is on the 10th at 359,800 km or 223,600 mi. Apogee is on the 22nd at 405,400 km or 251,900 mi.
Planets
Mercury is an evening object. It spends about the first third of the month in Leo. It doesn’t progress much into Virgo after that. The planet is at aphelion on the 23rd. It’s 0.467 astronomical units fro the sun. Greatest elongation is 27.3° east of the sun on the 27th. The planet and the sun are at a low angle to the horizon for northern hemisphere viewers. The Mercury-sun line is at a right angle to the horizon from about 25° south though. For lucky observers there, the planet sets two hours after the sun.
Saturn’s at opposition on the 14th. It’s 8.86 astronomical units from Earth on that date. For the first half of the month, you can see the planet rising sooner and sooner after sunset until opposition when it rises and sets opposite the sun setting and rising. After that, the ringed planet is already up when the sun goes down and you can see it higher in the sky each night as darkness begins. Also, look at Saturn in a telescope to see the gas ball’s shadow on the rings move from one side of the disk to the other. Around opposition, you may see a little shadow on each side. If your scope gives you such a view, try to also see the Cassini Division. It’s a gap in the rings. Saturn’s moon Mimas clears out the material there. Saturn’s retrograde all month in the eastern end of Capricornus.
Jupiter is retrograde. Although it’s alongside Pisces, it’s on the Cetus side of the boundary between the two constellations. It will be at opposition next month. You can start watching the big planet in a telescope to see its disk getting slightly bigger.
Mars starts the month close to Uranus. Mars is easy to see with the naked eye after midnight between the Pleiades and the head of Cetus. Uranus requires a telscope for most people, even though it’s just bright enough to be a naked eye object. Bright enough to see unaided doesn’t always mean big enough to see unaided. Orange Mars and blue Uranus cast their complementary colors 1.3° apart on the 1st and 2nd. Uranus stays almost exactly in the same spot among the stars all month while Mars moves eastward.
Although Mars is moving in the opposite direction as the stars behind it, they’re all rising earlier each morning. It’s on a trajectory that will place it between the Pleiades and the Hyades in the last few days of August.
On the first morning of the month, Venus is closing in on Wasat in Gemini. It passes just 0.2° from the star at 9 to 10 hours UT on the 2nd. You’ll have to be in the eastern Pacific Ocean to see them so close. Elsewhere, where the planet is up, so is the sun. Easter Island and Sala-y-Gomez are well positioned for it.
As the twins move up the pre-dawn eastern sky, Venus moves down. It’s firmly in Cancer by the 17th and 18th when it’s in the Beehive cluster. That’s worth a look in binoculars. On the 18th, it’s nearest Asellus Australis. The star on the other side of the Beehive is Asellus Borealis. They are the northern and southern donkeys, respectively. The Beehive cluster, now named for how it looks with magnification, has long been referred to as a manger from which the two donkeys feed.
In the last days of August, you may get a glimpse of Leo’s head with Venus in the vicinity of Algenubi.
The asteroid Vesta is at opposition on the 22nd. It’s an easy target for low magnification in dark skies.
The Perseid meteor shower could peak at 01 hours UT on the 13th.