Greetings from RFO (www.rfo.org).
July and August belong to Mars, which is at opposition and closest earth approach late this month, something that occurs only once every 2+ years. For a planet so near to us, we get only rather rare opportunities to observe it nicely. Unfortunately for us in the northern hemisphere, Mars is fairly far south this year. If you want to peer at Mars through a telescope, then this month, after midnight hours, or next month, in late evening hours, are the only really good chances.
Saturn is even further south and so provides even more limited observing opportunities. Still, it is now just past opposition so at its best for the year, with observing now moving into late evening hours. Jupiter is better placed and big and bright so remains a good target in the evening sky. But don't dawdle! Jupiter will be sinking into the sunset this fall.
The moon provides many nice observing and viewing opportunities this month, from conjunctions with planets and bright, colorful stars to thin crescents and a couple of bright star occultations ... and even causes large tides around the new moon, the first of two such months.
Even if you have no interest or opportunity for telescope observing, the bright planets and conjunctions and more are decorating the night sky all month so try to take some time and look up and appreciate what's happening up there!
JULY ASTRONOMY EVENTS TO WATCH FOR Note: All times are local Pacific Time and calculated for the RFO site.
* Use the "What's Up in the Night Sky" link on the RFO website for additional events and details.
Moon - The moon is near Mars around 12am on the morning of 7/1. Last Quarter is on the morning of 7/6. The crescent moon is very near the bright red-orange star Aldebaran in Taurus around 4:30am on 7/10; use binoculars to appreciate the star color and moon detail. New Moon is on the evening of 7/12 and occurs just 5 hours before perigee (closest approach to earth) so will cause large tides from about 7/13 to 7/15. Use binoculars to spot an ultra-thin 1.7% crescent moon 4° high 20° north of due west 20 minutes after sunset on 7/13 (or at 8:54pm calculated for the RFO site though hills will block the view from RFO). You can use the crescent moon on the evening of 7/14 to help you try to spot Mercury (see Mercury, below). Around 9pm on 7/15 look for the crescent moon very near Venus and the bright blue star Regulus (use binoculars). The first quarter moon is midday on 7/19. The moon is near Jupiter on the evening of 7/20 (see Jupiter below for more details). On the evening of 7/21 the moon will occult the star eta Librae (see below). On the evening of 7/24 the moon occults the star mu Sagittarii (see below). The full moon is very near Saturn around 11pm on 7/24. The full moon is near Mars around 11pm on 7/26 and 7/27. The "Buck" full moon is midday on 7/27.
Mercury - Mercury continues a moderately good evening apparition until about 7/17 with a maximum altitude 45 minutes after sunset of 8° on 7/5. However, Mercury fades as the month progresses becoming more challenging to spot so binoculars will be helpful. On the evening of 7/9 Mercury will be north of and lower than the close pair of Venus and Regulus (see below). On the evening of 7/14 Mercury will be directly below the thin 6% crescent moon, with Mercury's altitude 5° 40 minutes after sunset (or at 9:19pm calculated for the RFO site).
Venus - Venus is still prominent in the evening sky but becoming slightly less so as it rises less high each evening and drifts gradually southward. It sets around 10:30pm mid-month. Venus will be very near the bright blue star Regulus in Leo around 9pm on 7/9 (use binoculars), with Mercury a bit to the north and lower. The crescent moon joins Venus and Regulus around 9pm on 7/15.
Mars - In Capricornus, Mars rises around 9:30pm mid-month and is at opposition on the evening of 7/26. Mars reaches magnitude -2.8 and a disk size of 24.3" at opposition. Mars will be closest and largest around 1am on 7/31. This is the closest opposition since 2003 and Mars won't be this close again until 2035. However, the southern declination is very unfavorable for us northern observers, with Mars staying rather low in the southern sky. This means that this month and August are really the only good times for telescope observing of Mars this year. The moon is near Mars around midnight on the morning of 7/1 and then the full moon is near Mars on the evenings of 7/26 and 7/27, when Mars is at opposition... a nice reminder that planetary opposition is analogous to a full moon.
Jupiter - In Libra near the bright wide double star Zubenelgenubi (alpha Librae) all month (use binoculars), Jupiter ends retrograde motion on 7/10. Very bright and dominant in the southwest evening sky, Jupiter sets around 1:30am mid-month. Jupiter will be disappearing from view by late summer so good observing time is running short. The moon is near Jupiter around 10pm on 7/20. Jovian satellite events are still readily observable but starting to dwindle as Jupiter sets earlier; details on these on our website(*).
Saturn - Saturn, retrograde in Sagittarius, is just past opposition and still at its best for observing, setting around 4:30am mid-month. Its far southerly declination provides just a short window for the best observing of this favorite of targets this year so don't delay. The moon is very near Saturn around 11pm on the evening of 7/24.
Occultation of Eta Librae - At about 10:21pm on 7/21 the magnitude 5.4 star eta Librae will disappear behind the moon's dark limb 54° from the south cusp. (Calculated using Occult4 for the RFO site. Details will differ as distance from RFO increases.)
Occultation of Mu Sagittarii - At about 8:36pm on 7/24 (during civil twilight in the RFO region) the magnitude 3.8 star mu Sagittarii will disappear behind the moon's dark limb 40° from the north cusp. (Calculated using Occult4 for the RFO site. Details will differ as distance from RFO increases.)
TIME SEQUENCE SUMMARY OF EVENTS: Capitalized items refer to the sections above.
6/19 to 7/17 - MERCURY in the west
7/01 - MOON near MARS
7/06 - Last Quarter MOON
7/09 - VENUS very near Regulus and near MERCURY
7/10 - Crescent MOON very near Aldebaran
7/10 - JUPITER ends retrograde motion
7/12 - New MOON
7/13 to 7/15 - Large Tides due to New MOON near perigee
7/13 - 1.7% Crescent MOON in west
7/14 - 6% Crescent MOON near MERCURY
7/15 - Crescent MOON near VENUS & Regulus
7/19 - First Quarter MOON
7/20 - MOON near JUPITER
7/21 - OCCULTATION OF ETA LIBRAE
7/24 - OCCULTATION OF MU SAGITTARII
7/24 - MOON very near SATURN
7/26 - MARS at opposition
7/26 - MOON near MARS
7/27 - "Buck" Full MOON
7/27 - MOON near MARS
7/31 - MARS closest to earth