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August 2017 Skies

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August Skies

by Dick Cookman


Highlights: Comet Journal, Martian Landers, Meteor Showers, Solar Eclipse, Planet Plotting, August Moon

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

Comet Journal

Comet C/2017 O1 is in Cetus and Eridanus in early August and moves northward into Taurus late in the month. It is at 9th magnitude and expected to brighten to 8th magnitude. C2015 ER61 (PanSTARRS) is in Aries and Taurus after passing through perihelion at 6th magnitude in May. It is at 9th magnitude and will continue to circle through the two constellations as it retreats from the inner solar system. Comet V2 Johnson, in southern hemisphere skies, is visible in southern USA at 8th magnitude in Lupus in early August.

Mars Landers

Opportunity is at "Perseverance Valley” on the western rim of "Endeavor Crater", the 14 mile wide crater located on "Meridiani Planum", the plain where the rover landed in January of 2004. Between Sol 4774 (June 28, 2017) and Sol 4793 (July 18, 2017), Opportunity entered the valley and moved to a position offering a favorable tilt for solar energy gain prior to and after the solar conjunction on July 26th. In addition, two weeks of instructions were uploaded for the conjunction due to expected communication difficulties during the conjunction. On Sol 4795, a computer warm reset halted use of the stored sequence of commands and kicked the rover into automode during which it awaits further instruction. Solar array energy production averaged 342 watt-hours per sol during the month and the rover has traveled 27.95 miles (44.97 kilometers) on Mars since 2004.

On Sol 1741 (June 29, 2017), Curiosity was preparing for the solar conjunction and drawing close to the base of Vera Rubin Ridge, the hematite bearing layer which is the next youngest layer above the Murray Formation mudstones. Analysis of the hematite rocks may reveal an ancient environmental change to more acid conditions in the water filling the crater. The layers of Mt. Sharp which lay above the ridge include more recent clay and sulfate bearing rocks which will reveal further details of Martian history.

Meteor Showers

Residual Southern Delta Aquarid Meteors which continue to grace the skies in early August after peaking on July 30th compete with glare from the gibbous Moon. On the 8th, the day after the partial eclipse of the Moon, the minor Northern Delta Aquarid Shower adds a few meteors piercing the lunar glare each hour.

The big bopper for August is the Perseid Meteor shower coinciding with the waning gibbous Moon on the nights of the 11th and 12th. Debris from former passages of Comet Swift-Tuttle fuels the Perseids which appear to come from the direction, or radiant, of the constellation Perseus, residing in the north-eastern part of the sky. The Perseids are renowned due to their appearance during the warm evenings and mornings of early August and a typical meteor count of 60 to 100 meteors per hour.

The Kappa Cygnids on the 18th and Iota Aquarids on the 20th are minor showers averaging 2 meteors per hour.

Solar Eclipse

We live in an era characterized by a phenomena unique in Earth history. The Moon has been retreating from the Earth during the last few billion years and now the Sun is 400 times farther than the Moon. Since the Sun is also 400 times larger, both subsume the same angle in the sky permitting the Moon to totally block the Sun during New Moon phases when the Sun, Moon, and Earth are lined up. Eclipses occurring when the Moon is at aphelion or farthest from Earth in its orbit are characterized by annular eclipses with the outer perimeter of the Sun surrounding the Moon in a “Ring of Fire”. The last annular eclipse for most of the USA was on 5/10/1994 and the next will be on 10/14/2023. The last total eclipse was on 2/26/1979 in the northwest USA from Washington and Oregon to North Dakota, and the last seen from coast to coast was in June, 1918. The next will be on 4/8/2024.

The August 21st solar eclipse will be total for areas in an ~ 70 mile wide swath stretching from the coast of South Carolina to that of Oregon. The Moon’s shadow will make the trip from west to east at 1700 miles per hour. All areas of the continental USA will see at least a partial eclipse with more than half of the Sun blocked by the New Moon. #14 welding glass is the minimum retina protection required to look at the Sun and stacking 2 #7’s does not provide sufficient protection. Eclipse blindness is a very real outcome of inadequate protection. Solar glasses with a (ce) marking can be used, and solar glasses with optical lenses provide much clearer views, enabling observers to see the larger sunspots and details of Baily’s Beads and the Diamond Ring Effect caused by the disappearing or emerging Sun peeking between lunar mountains.

Planet Plotting

Morning planets include Venus (-3.9 to -3.8) in Gemini and Cancer. Mars (+1.7 to +1.8) is in Cancer and Leo in August. Uranus (+5.8) is in Pisces, and Neptune (+7.8) is in Aquarius. Brilliant Venus rises about 4:00AM EDT and spends most of August about 30° above the horizon at sunrise at 40° N latitude. It is near the waning crescent Moon on the 19th,. Uranus and Neptune rise about midnight and are in the southern sky before dawn. The Moon is adjacent to Neptune on the 13th and Uranus on the 16th.

Evening planets in August include Mercury (+0.6 to +4.7 to +0.4) in Leo, Sextans, and back into Leo. It is near the waxing crescent Moon in Sextans on the 22th, at inferior conjunction on the 26th, and reappears in the morning sky in September. Jupiter (-1.7 to -1.6) in Virgo is in the west after sunset. It sets about 11PM EDT early in the month and falls into the glare of sunset by month’s end. Saturn (+0.3 to +0.4) is in Ophiuchus in August. It is adjacent to the Moon on the 3rd and 30th and dims slightly in late August.

PlanetConstellation(s)MagnitudePlanet Passages Time Date
SunGemini, Cancer-26.8New Moon2:30PM EDT 8/21
MercuryLeo, Sextans, Leo+0.6 to +4.7 to +0.6 Inferior Conjunction 4.22° S5:00PM EDT8/26
VenusGemini, Cancer-3.9 to -3.8  
MarsCancer, Leo+1.7 to +1.8  
JupiterVirgo-1.7 to -1.6  
SaturnOphiuchus+0.3 to +0.4  
UranusPisces+5.8 to +5.7  

August Moon

The August 21st New Moon at 2:30PM EDT blocks out the Sun producing a solar eclipse as described above. It is the beginning of Lunation 1171 which ends 29.46 days later with the New Moon of Sept. 20th at 1:30AM EDT.

The Full Moon of August in Virgo occurs at 2:12PM EDT on the 7th. The August Moon is called the “Green Corn or Grain Moon”. Colonial Americans called it the “Dog Day’s Moon”. To the Celts it was the “Dispute Moon”, and Chinese refer to it as “Harvest Moon”. It was the “Corn Moon” in Medieval England. Anishinaabe (Odawa and Ojibwe) people in northern Michigan recognize it as “Manoominike-giizis " (Ricing Moon).

Lunar Apogee position in orbit (maximum orbital distance) is at 251,714 miles (63.51 Earth radii) from Earth on the 2nd at 2PM EDT. The Moon will again reach apogee on the 30th at 8AM EDT when it is at 251,239 miles (63.39 Earth radii). Perigee (closest to Earth) is 227,498 miles or 57.40 Earth radii on the 18th at 9:16AM EDT.

PlanetConstellationMagnitudeMoon PassageMoon PhaseMoon Age
SunLeo-26.82:30PM EDT, 8/21New0 days
MercurySextans+3.85.9°NNE, 5:00AM EDT, 8/22Waxing Crescent0.60 days
VenusGemini-3.92.2°S, Midnight EDT, 8/19Waning Crescent26.76 days
MarsLeo+1.81.5°SSW, Midnight EDT, 8/21Waning Crescent28.76 days
JupiterVirgo-1.63.3°NNE, 11:00AM EDT, 8/25Waxing Crescent3.85 days
SaturnOphiuchus+0.33.4°N, 4AM EDT, 8/3Waxing Gibbous10.93 days
SaturnOphiuchus+0.43.5°N, 11AM EDT, 8/30Waxing Gibbous8.85 days
UranusPisces+5.84.2°SSE, 4AM EDT, 8/13Waning Gibbous20.93 days
NeptuneAquarius+7.80.82°SSE, 7PM EDT, 8/9Waning Gibbous17.55 days

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