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July 2018 Skies

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July Skies

by Dick Cookman


Highlights: Comet Journal, Martian Landers, Meteor Showers, Planet Plotting, July Moon

Focus Constellations: Leo, Coma Berenices, Bootes, Corona Borealis, Hercules, Ophiuchus, Aquila, Lyra, Cygnus, Cepheus, Draco, Ursa Major, Ursa Minor, Cassiopeia, Camelopardalis

Comet Journal

C/2016 M1 (PanSTARRS) is brightening to 9th magnitude for southern hemisphere observers but is not visible in the northern hemisphere. C/2016 S3 (PanSTARRS) is also at 9th magnitude as it travels through Camelopardalis in July. It will brighten slightly when approaching perihelion on August 15th. 21P/Giacobini-Zinner (2018) is approaching 8th magnitude and is moving northward through Cygnus and Cepheus in July. It is expected to reach 6th magnitude at perihelion in September and may even reach naked eye visibility. It is a short term comet with an orbital period of 6.55 years.

Mars Landers

Opportunity is halfway down the approximately 656-feet (200-meter) Perseverance Valley on the west rim of Endeavour Crater, pursuing evidence for support of one of several hypotheses as to the origin of the valley. At the end of May a nearby dust storm approached the rover. By June 10th the storm enveloped the rover and caused loss of communication. Since the last contact with the rover, Opportunity probably experienced a low-power fault, causing the onset of sleep mode which will end only when the skies eventually clear and the batteries are recharged. By the 20th the storm grew in size, encircling the planet. This phenomena can occur during summer for the southern hemisphere of Mars when dust particles in the air absorb and transfer heat into the air causing increasing wind velocity. This effect is exaggerated as Mars approaches perihelion and receives increasing amounts of solar energy. Perihelion will occur on Sept. 16th. Some Mars observers believe that the dust storms occur in order to diminish their telescopic views of the planet, a hint that the God of War feels that his appearance and actions are none of their business.

At the end of May, after completing examination and crossing of the long sought hematite unit known as Vera Rubin Ridge, and conducting observations of the terrain farther north, Curiosity was able to successfully drill and extract samples from a large rock dubbed Duluth from the Blunts Point Member of the Murray formation. The drilling samples were then delivered to the two laboratories within the rover. The laboratories are designed to conduct chemical and mineralogical analysis. This huge accomplishment finally compensated for the Dec. 16, 2016 failure of the drilling equipment and procedures which paralyzed the drilling program, one of the major functions of the rover. Mission scientists finally overcame the drilling and delivery problems by creating new techniques for which the rover was never designed. This permitted resumption of the drilling program which was planned to provide rock, sediment, and atmospheric composition data which can be utilized to investigate the possibilities of life during Martian geologic history.

Following the success at Duluth, Curiosity turned to the south and headed back toward the crest of Vera Rubin Ridge. The rover surmounted the ridge by Sol 2094 (6/28/18), moved out onto the flatter terrain to the south, and resumed its climb the flank of Mt. Sharp.

Meteor Showers

According to Guy Ottewell’s 2018 Astronomical Calendar, July hosts the following meteor showers: July 28 SAT.: Piscid Austrinids. Active Jul 15- Aug 10. ZHR ~5. Near Full Moon. July 28 SAT.: July Gamma Draconids? Peak 12:30 UT? ZHR ~20. 1 day after Full Moon. Very unfavorable. July 30 Mon.: Southern Delta Aquarids. Active Jul 12-Aug 23. ZHR ~25. 2 days after Full Moon. Very unfavorable. July 30 Mon.: Alpha Capricornids. Active Jul 3- Aug 15. ZHR ~5. 23 km/sec. 2 days after Full Moon.

The first two showers have no known progenitors and last two showers may result from streams of debris from Comet 96P/Machholz and minor planet 169P/NEAT.

Planet Plotting

Venus (-4.1 to -4.3) is in Leo in July and approaches Virgo at month’s end. It sets about 2 hours after sunset throughout July, and easily dominates the western evening sky. The waxing crescent Moon passes within 2.0° of Venus on the 15th. Mercury is below and slightly north of Venus and sets slightly more than an hour after the Sun. It is brighter in early July and sinks into the glow of sunset during the month as it moves from Cancer into Leo. It is at maximum eastern elongation (26.4°) on the 12th and within 2.0° of the waxing crescent Moon on the 14th. Jupiter (-2.2 to -2.0) is in Libra in the southern and southwestern evening sky. It is near the waxing gibbous Moon on the 20th. In July, Saturn (+0.0 to +0.2) in Sagittarius rises in the southeast as the Sun sets. The waxing gibbous Moon passes the ringed planet at 2AM EDT on the 25th.

July is the Month of Mars (-2.2 to -2.8), which reaches opposition in Capricornus on the 27th and is closest to Earth (0.385 AU) on the 31st. This is its best opposition since 2003. Preceding close oppositions include 1956 - 0.379 AU, 1971 - 0.376 AU, and 2003 - 0.373 AU. The 1956 opposition was when Dick Cookman made detailed telescopic observations and determined that Percival Lowell was in error in his estimation that Mars had canals. More recent observation have confirmed Cookman’s determination and world governments have conducted numerous Martian orbital expedition and landings to further support his observations.

PlanetConstellation(s)MagnitudePlanet PassagesTime, Date
SunGemini/Cancer-26.8New Moon10:48PM EDT, 7/12
MercuryCancer/Leo+0.0 to +2.8Max. Eastern Elongation1:00AM EDT, 7/12
VenusLeo-4.1 to -4.3  
MarsCapricornus-2.2 to -2.8Opposition
Closest to Earth
1:00AM EDT, 7/27
4:00AM EDT, 7/31
JupiterLibra-2.2 to -2.0  
SaturnSagittarius+0.0 to +0.2  
NeptuneAquarius+7.9 to +7.8  

Although Mars is slightly farther (0.385 vs. 0.373), dimmer (-2.8 vs. -2.9), and smaller (24.3” vs. 25”) during this opposition than that of 2003, observers will benefit from the higher arc above the southern horizon that Mars takes through the sky as there will be less atmospheric distortion.

In early July Mars already is 20.9” in diameter and since it rotates slightly slower than Earth, observers may see a slightly different view of the planet each night and cover its entire sphere with consecutive observations during the course of July. A good telescope with a 4-5”+ aperture and a good quality eyepiece providing 140X+ magnification will reveal views sufficient to see surface details if the planet-wide dust storm settles down during the month.

The Full Moon will be higher than Mars in the southern sky and will also occur in Capricornus a little more than 15 hours after opposition, producing significant glare during the best nights of this opposition. Observers may moderate lunar glare by waiting until the predawn hours on the nights preceding the opposition when the Moon sets before Mars. After opposition, the best viewing will be after sunset when Mars rises before the Moon.

July Moon

The New Moon of July on the 12th at 10:48PM EDT is the beginning of Lunation 1182 which ends 29.26 days later with the New Moon of August on the 11th at 5:58AM EDT. The Full Moon in on the 27th at 4:20PM EDT is known as the “Thunder or Hay Moon.” Celts called it “Moon of Claiming,” and Colonial Americans called it “Summer Moon.” Chinese refer to it as “Hungry Ghost Moon,” and it was the “Mead Moon” in Medieval England. Anishinaabe (Odawa and Ojibwe people) recognize it as “Miin-giizis” (Berry Moon.) Eastern hemisphere observers will be treated to a total lunar eclipse on the night of the 27th, allowing them a full view of Mars in its glory near opposition.

Lunar Perigee (closest to Earth) is 222,500 miles or 56.04 Earth radii on the 10th at 2:07PM EDT. Apogee (maximum orbital distance) occurs on the 23rd at 7:23 AM EDT when the Moon is at 252,119 miles (63.69 Earth radii).

PlanetConstellationMagnitudeMoon PassageMoon PhaseMoon Age
SunGemini-26.810:48PM EDT, 7/12New0 days
MercuryCancer+0.72.0°N, 6:00PM EDT, 7/14Waxing Crescent1.80 days
VenusLeo-4.21.6°N, Midnight EDT, 7/15Waxing Crescent2.05 days
MarsCapricornus-2.87.0°N, 6:00PM EDT, 7/27Waning Gibbous14.80 days
JupiterLibra-2.04.0°N, 8:00PM EDT, 7/20Waxing Gibbous7.78 days
SaturnSagittarius+0.22.0°N, 2:00AM EDT, 7/25Waxing Gibbous12.13 days
UranusAries+5.85.0°S, 10:00AM EDT, 7/7Waning Crescent23.76 days
NeptuneAquarius+7.93.0°S, 8:00PM EDT, 7/3Waning Gibbous20.18 days
NeptuneAquarius+7.83.0°S, 2:00AM EDT, 7/31Waning Gibbous18.13 days


Digital Don
Jul 08 2018 12:08 AM

I believe the second comet PanSTARRS listed above should be C/2017 S3 not 2016.

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