1 July. First Quarter Moon, 00:51 UT
1 July. The first quarter Moon joins Jupiter and the bright star Spica in the southwestern sky. Jupiter is west of Spica and much brighter. This is more or less the last month to get a good view of the planet as it continues to fade, grow smaller, and appear lower in the southern or southwestern sky during July. It’s still brighter than any star and a beautiful sight in a small telescope.
3 July. Earth reaches aphelion, its furthest point from the Sun in its orbit. Today the planet lies 152,092,504 km (94,505,901 miles) from the Sun.
6 July. The planet Saturn lies about 3º south of the waxing gibbous Moon. The rings of this planet are dramatically tilted this month, and the planet is still bright and relatively big as it drifts through the constellation Ophiuchus in the southern sky. It’s quite far south during this apparition, which favors southern stargazers, but northerners with patience and steady sky can still glimpse much detail in a small telescope.
9 July. Full Moon, 04:07 UT
10 July. With a pair of binoculars, look for the planet Mercury low over the western horizon just after sunset. Today, it’s tangled among the stars of the Beehive Cluster, M44, in the constellation Cancer. Mercury makes a modest apparition above the western horizon this month for northern observers (you get a better view from the southern hemisphere). At magnitude -1.0 at the beginning of July, the planet is impressively bright but somewhat obscured by the twilight sky. By month’s end, the planet dims to magnitude +0.4 as it moves back towards the Sun.
11 July. Look for the brilliant planet Venus, the Pleiades and Hyades star clusters, and the bright star Aldebaran in a straight line in the eastern sky before dawn. Venus rises in the east a couple of hours before the Sun this month. It’s about 20º above the horizon as the Sun comes up. In a telescope, the planet displays a gibbous phase and its disk slowly gets smaller as July progresses.
16 July. Last Quarter Moon, 19:26 UT
20 July. A beautiful sight in the eastern summer pre-dawn sky, the slender waning crescent Moon joins dazzling Venus. The two objects are just 4º apart, approximately, just a little more than the width of two fingers held at arm’s length.
23 July. New Moon, 09:46 UT
23-25 July. Mercury, the bright star Regulus, and a very slender crescent Moon congregate just over the western horizon after sunset. Bring binoculars! By July 25th, Regulus and Mercury are just 1º apart.
27 July. Mars reaches conjunction with the Sun and remains invisible in our skies. But in one year– July 27, 2018– Mars will reach opposition in the constellation Capricorn and grow as big and bright as it’s been in 15 years.
27-28 July. The Delta Aquarid meteor shower peaks. This annual event favors observers in the southern hemisphere and southerly latitudes in the northern hemisphere, though all observers can see some of these slow-moving meteors. The Delta Aquariids appear to radiate from a point near the star Skat (delta Aquarii) in the constellation Aquarius. The shower peaks around July 27-30, but unlike most meteor showers, the Delta Aquarids lack a sharp maximum so meteors are visible from mid-July through early August. The maximum hourly rate can reach 15-20 meteors in a dark sky.
30 July. Mercury reaches its greatest eastern elongation 27º from the Sun.
31 July. First Quarter Moon, 15:23 UT