Star Calendar – September 2016

Star Calendar

September 2016

Star Calendar Planets:

Moon is New fairly near the Sun’s passing through the middle of eclipse season (near a moon node) but is also near apogee so that it is too distant for its shadow tip to reach earth, making an annular eclipse. Full Moon occurs as the Sun is leaving the realm of the node – making a penumbral lunar eclipse then. Neither event is visible in Spring Valley or our hemisphere. A second New Moon occurs as September closes – but the Sun is then well out of the realm of eclipse-making geometry. The Harvest Moon is a period when the skies never really get dark – making outdoor work possible into the night and/or early morning. This year the Full Moon rises in Civil Twilight and does not set until 2 hours after the following sunrise. The effect is stronger when the Moon is well north of the ecliptic – which it isn’t this year.

Mercury scoots back into the morning sky for a more favorable appearance in the second half of this month. Even though the excursion from the Sun makes a much smaller angle than the last one, the steepness of the ecliptic in morning skies at this time make an overwhelming advantage for us. A crescent Moon aids on the 28th and 29th.

Venus sidles up to Spica during the first half of this month, and overwhelms in the second half. Spica is the signature star of Virgo and may be found by following the curve begun by the handle of the Dipper – through yellow-green Arcturus and about that distance again to whitish Spica. Venus is approaching us, getting larger in angular size, and waning gibbous in phase.

Sun crosses the celestial equator, then rises and sets south of east and west until spring. The alternation of presence in the sky for longer and shorter portions of the day is imitated, in different periods by all of the planets – see Jupiter.

Mars starts making tracks away from the Scorpion and toward the Teapot/Archer this month. When he begins to move out he also fades in brilliance. Remember how bright he was compared to Antares in August? He will diminish to equal brightness by January.

Jupiter crosses the celestial equator near his conjunction with the Sun this month. Jupiter will also fall south of the celestial equator, but, unlike the Sun, will remain there for 5 ½ years. One could call this period an autumn and winter for Jupiter. He will next cross the summer colure in June of 2025.

Saturn begins the month above Antares and begins direct motion into Ophiucus in earnest. The Moon stands above the pair on the 6th.

Star Calendar Days:

  1      Sunrise/sunset in Spring Valley at 6:23/19:28 (13h5m daylight)

          New Moon at 5AM, annular solar eclipse S.Africa, Madagascar, Antarctic

  2      Very young Moon grazes Jupiter low in west, setting around 8:PM

  3      Young Moon above Venus, evening in west

  8      Moon above Saturn, SW at 9:PM

  9      Moon above Mars, SW at 10:PM

13      Mercury crosses near-side of Sun

16      Full Harvest Moon at 15:05, penumbral lunar eclipse for Indian Ocean hemisphere

17-18 Venus passes to above and left of Spica, low-western evening sky

21      Mercury is stationary to stars, visible in low east at 6:AM

          Jupiter crosses to south of celestial equator – remains there until May 26, 2022!

22      Center of Sun crosses celestial equator, autumnal equinox, at 10:21 EDT

          Sunrise/sunset at 6:44/18:53 (12h9m daylight)

25      Sun’s upper limb just tangent to southern edge of celestial equator –

          Sunrise/sunset at 6:47/18:47 (12h0m daylight) equal day and night

26      Jupiter crosses far-side of Sun (conjunct)

28      Mercury at greatest angle from Sun, 18 degrees, for this appearance

          Mercury below waning Moon, low East around 6:AM

29      Mercury just below/right of old Moon, low East around 6:AM

30      Another New Moon for this month, 8:PM

About the Recent Lunar Eclipse

By the Dark of the Moon …

… indeed the last eclipse was darker than most — but not as dark as I had hoped for.

From Spaceweather.com:

“LUNAR ECLIPSE DETECTS GLOBAL COOLING (BUT ONLY A LITTLE): On Sept. 27th, people on five continents watched the Moon pass through the shadow of our planet. Most agreed that the lunar eclipse was darker than usual. Little did they know, they were witnessing a sign of global cooling. But only a little.


Above: “The eclipse was truly dark,” says photographer Giuseppe Petricca of Pisa, Italy

Atmospheric scientist Richard Keen of the University of Colorado explains: “Lunar eclipses tell us a lot about the transparency of Earth’s atmosphere. When the stratosphere is clogged with volcanic ash and other aerosols, lunar eclipses tend to be dark red. On the other hand, when the stratosphere is relatively clear, lunar eclipses are bright orange.”

This is important because the stratosphere affects climate; a clear stratosphere ‘lets the sunshine in’ to warm the Earth below. At a 2008 SORCE conference Keen reported that “The lunar eclipse record indicates a clear stratosphere over the past decade, and that this has contributed about 0.2 degrees to recent warming.”

The eclipse of Sept. 27, 2015, however, was not as bright as recent eclipses. Trained observers in 7 countries estimated that the eclipse was about 0.4 magnitude dimmer than expected, a brightness reduction of about 33 percent.

What happened? “There is a layer of volcanic aerosols in the lower stratosphere,” says Steve Albers of NOAA. “It comes from Chile’s Calbuco volcano, which erupted in April 2015. Six months later, we are still seeing the effects of this material on sunsets in both hemispheres–and it appears to have affected the eclipse as well.”

Volcanic dust in the stratosphere tends to reflect sunlight, thus cooling the Earth below. “In terms of climate, Calbuco’s optical thickness of 0.01 corresponds to a ‘climate forcing’ of 0.2 Watts/m2, or a global cooling of 0.04 degrees C,” says Keen, who emphasizes that this is a very small amount of cooling. For comparison, the eruption of Pinatubo in 1991 produced 0.6 C of cooling and rare July snows at Keen’s mountain home in Colorado.

“I do not anticipate a ‘year without a summer’ from this one!” he says. “It will probably be completely overwhelmed by the warming effects of El Nino now under way in the Pacific.”

This lunar eclipse has allowed Keen measure the smallest amount of volcanic exhaust, and the smallest amount of resultant “global cooling” of all his measurements to date. And that is saying something considering that he has been monitoring lunar eclipses for decades.

“This is indeed the smallest volcanic eruption I’ve ever detected,” says Keen. “It gives me a better idea of the detection capabilities of the system (eclipses plus human observers), so when I go back into the 1800s I can hope to find similarly smallish eruptions in the historical record.”

Paul Davis

Star Calendar – September, 2015

Star Calendar

September 2015

Star Calendar Planets:

Moon will be waning as September opens and the ecliptic especially steep to the horizon in the morning. This circumstance will show especially thin and horizontal crescents on the 11/12th. New Moon begins the Hebrew new year (Rosh Hashanah) 5776 Anno Mundi. Moon’s ascending node currently lies where the Sun stands on the 24th, making this month an eclipse season. On the 13th the New Moon will be at an extreme apogee and its shadow will not reach the earth; a partial solar eclipse (for those near South Africa and the proximate part of Antarctica). However the Full and most perigee Moon of the 27–28th may well yield an especially dark lunar eclipse. A dark Moon is hard to see and is much more creepy than a red/yellow one; it looks like a giant stone hanging in the sky.

Mercury makes a large angle from the evening Sun on the 4th — but suffers from a shallow ecliptic. One may catch a peek around then, low in the west at 8PM. Mercury begins retrograde motion on the 17 and crosses the nearside of the Sun on the 30th.

Venus brightens to a maximum magnitude (for the year) of -4.8 on the 20th. She is receding from us and waxing in phase but is brightest while still crescent. The angular area Venus occupies in the sky diminishes as she recedes, that area being maximal on the 21st — when the waxing phase briefly overtakes the diminishing of receding distance.

Sun crosses the celestial equator on the 23rd, its center crossing at 4:21AM. The day of equinox is still 3 minutes longer than night though, a 12-hour-night waits for the 25/26th. Success in balancing eggs on their ends at equinox only indicates a greater patience and diligence in the attempt. There is no special gravity or balance-energy that day. Sorry.

Mars defers to Venus these mornings and passes (slightly dimmer than and) close to Regulus on the 25th, while bracketed by Venus above, Jupiter below.

Jupiter will be noticed emerging from his sunbath some fine morning this month, appearing below and much brighter than Regulus in the east. Weather and horizon permitting, look for it while scouting for old crescent Moons in the east at 6AM on the 11/12th.

Saturn is in the lower SW in the evening, and is the brightest celestial object in the vicinity. The Moon will be nearby on the 18th. Continue reading

Star Calendar — September 2007

Star Calendar

September 2007

Star Calendar Planets:

Mercury will make a poor appearance in the western evening sky in mid-September. It will dash to the eastern morning sky by late October.

Venus will quickly rise into the eastern pre-dawn sky in September and will shine beside Regulus and Saturn by early October. On October 7th the waning Moon will join them.

Mars rises in the middle of the night in the horns of Taurus as September opens. It rises earlier in the evening and brightens as the weeks pass. Mars makes its highest and longest path across our sky on October 1st when it is of Betelgeuse of Orion – best seen in the south at about 6:00 AM.

Jupiter lingers in Ophiucus above Antares and is in the south at sunset as September begins. It slowly accelerates its direct motion and fades eastward toward the setting Sun.

Saturn appears close to Regulus in the eastern morning sky in mid-September. It may be visible under the waning Moon on September 9th and will have a sojourn with Venus a month later.

As seen from the Apollo 15 landing site; central Earth-side of the Moon and about 25° north of the Moon’s equator: Continue reading