May 2015


May is the month that we begin to trade early sunsets for great weather.  Although the weather is warmer, it takes seemingly forever for it to get dark enough to observe the night sky. The end of civil twilight is at 8:45pm and the end of astronomical twilight is at 9:20pm, and keeps getting later through the Summer Solstice in late June. Be sure to take every opportunity to just go outside and look up. Star gazing is just that easy. As interest is piqued, spend some cloudy nights reading about anything that you’ve seen night sky.

About Scope Out      How to begin Observing the Night Sky


The sky map below represents the sky as it will appear in mid-May at the end of astronomical twilight, or the arrival of complete darkness, at 9:20pm 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 May 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 April’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.

The May Sky at Nightfall, Jim Johnson, December 2014.


Colors of the planets. This picture is not to scale. Image from NASA’s Planetary Photogrounal at

Mercury is in its best evening apparition of this year at the beginning of the month, peaking around May 10th, and remaining visible most of the remainder of the month. Look for it low on the western horizon about 45 minutes after sunset. The Pleiades, an easy naked eye object when it is overhead, can be seen with binoculars just to the right of Mercury. Mars will be a difficult, telescope-only object as it will soon disappear into the Sun’s glare. Look for it low on the western horizon about 45 minutes after sunset. Venus is the very bright object in the western sky after sunset. It is near its peek elongation from the Sun, and presents an appearance similar to the 1st quarter moon (half dark and half lit). Jupiter is the bright object that appears nearly overhead at nightfall. The show to watch over the next two months is Jupiter and Venus moving ever so closer to one another as they approach conjunction this summer. Take note of how many hand widths apart they are now (and write it down!), and check again every few nights. Saturn rises in the east at sunset and is in good viewing a few hours later. Uranus and Neptune are morning objects that rise just before dawn.


moon_phases_small_full May 3
Full Moon
moon_phases_small_lastqtr May 11
3rd Quarter
moon_phases_small_new May 18
New Moon
May 20 and 21
Conjunction with Venus
May 23
Conjunction with Jupiter
moon_phases_small_firstqtr May 25
1st Quarter
May 31
Conjunction with Saturn

© James R. Johnson, 2015

Leave a Reply

Your email address will not be published. Required fields are marked *