July 2015

INTRODUCTION

Summer’s heat is here and it is vacation season. Vacations are often an opportunity to get away from the city lights, so if you happen to be so lucky, be sure to take advantage of every opportunity to enjoy a much darker, and hence starrier night sky than what you might be accustomed to at home. In addition to being prepared for the cool nights that occur even during the summer, be sure to bring along something to keep the bugs away.

About Scope Out      How to begin Observing the Night Sky

THE CONSTELLATIONS

The sky map below represents the sky as it will appear in mid-July at the end of astronomical twilight, or the arrival of complete darkness, at about 10pm EDT. The Scope Out monthly focus is on the constellations that are  just to either side of the meridian, which is near the 12th hour (12h) of right ascension line in the July sky map. For a primer on how to use this sky map, please read How to begin Observing the Night Sky.

Scope Out divides the celestial sphere into three zones to aid in finding constellations:

1. Circumpolar Constellations: Find Usra MinorUrsa Major and Canes Venatici in the northern sky above Polaris.

2. Northern Constellations:  Find July’s remaining northern constellations, Leo, Leo Minor, Coma Bernices, Bootes and Corona Borealis near the zenith.

3. Southern Constellations: The best-placed constellations in April are Crater, Corvus, and Virgo. Some of these, Crater and Corvus, for example, never rise very far above the horizon because of their deep southern declination.

July
The July Night Sky, Jim Johnson, December 2014.
THE PLANETS
planets

Colors of the planets. This picture is not to scale. Image from NASA’s Planetary Photogrounal at http://photojournal.jpl.nasa.gov/

Mercury begins the month as a morning object, just past its peak for optimal viewing. Look for it in the eastern morning sky about 75 minutes before sunrise. It quickly dives back into the sun’s glare and is lost by month’s end. Venus and Jupiter are the bright pair in the western sky just after sunset.  They are just one day past a very close conjunction as the month begins, and they will travel together while remaining in relatively close proximity to one another. They will  appear just a bit closer to the western horizon with the passing of each evening. Venus‘ telescopic appearance will change dramatically during the month, beginning as a rather thick crescent, and then closing the month as a fingernail crescent. Venus’ apparent disk will appear noticeably large as well as the month progresses. Mars begins to emerges as a morning object by month’s end, and will be difficult to see without binoculars. Look for it near Mercury about 45 minutes before sunrise on the eastern horizon on July 16th. Saturn is just past its optimum viewing position with respect to disk size and brightness. It is placed higher in the sky for easier viewing at nightfall. Uranus and Neptune are morning objects that rise just before dawn.

THE LUNAR CALENDAR

moon_phases_small_full July 1
Full Moon
moon_phases_small_lastqtr July 8
3rd Quarter
moon_phases_small_new July 15
New Moon
July 18
Conjunction with Venus and Jupiter
moon_phases_small_firstqtr July 24
1st Quarter
July 25
Conjunction with Saturn
moon_phases_small_full July 31
Full Moon (aka Blue Moon)

Events

Earth reaches Aphelion – July 6

The Earth reaches its farthest distance from the Sun during its annual orbit about the Solar System’s star. There are no direct observables for the casual astronomer, but if the Earth were at perihelion, or the closest distance to the Sun, on this date, northern hemisphere summers would be noticeably warmer.

Very close grouping of Moon, Venus and Jupiter – July 18

Look for a very pretty grouping of a fingernail crescent Moon with Venus and Jupiter low on the western horizon right after sunset.

Blue Moon – July 31

The occasion of a second full moon during a calendar month is known as a “blue moon.” July’s first full month was on July 1st.

© James R. Johnson, 2015
jim@jrjohnson.net

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