September 2011 Celestial Calendar & Observing Notes courtesy of Dave Mitsky

[Big Dipper]

September 2011 Celestial Calendar & Observing Notes courtesy of Dave Mitsky (calendar data also reproduced in our forum calendar).

All times, unless otherwise noted, are UT.

9/2 Asteroid 192 Nausikaa (magnitude 8.3) is at opposition at 3:00

9/3 Mercury is at the ascending node today; Mercury is at greatest western elongation (18 degrees) at 6:00

9/4 First Quarter Moon occurs at 17:39

9/5 The Lunar X (the Purbach or Werner Cross), an X-shaped illumination effect involving various rims and ridges between the craters La Caille, Blanchinus, and Purbach, is predicted to occur at 0:18

9/8 Mercury is at perihelion today

9/9 Mercury is 0.7 degree north of the first-magnitude star Regulus (Alpha Leonis) at 2:00

9/10 Mars is 6 degrees south of the first-magnitude star Pollux (Beta Geminorum) at 2:00; Neptune is 6 degrees south of the Moon at 21:00

9/12 Full Moon (known as the Barley, Corn, or Fruit Moon), this year’s Harvest Moon, occurs at 9:27

9/13 Uranus is 6 degrees south of the Moon at 18:00

9/15 The Moon is at apogee, subtending 30 arc minutes from a distance of 406,065 kilometers (252,317 miles), at 6:00

9/16 Pluto is stationary at 12:00; asteroid 1 Ceres (magnitude 7.7) is at opposition at 17:00; Jupiter is 5 degrees south of the Moon at 18:00; asteroid 2 Pallas is stationary at 22:00

9/18 Mercury is at its greatest heliocentric latitude north today; asteroid 4 Vesta is stationary at 2:00

9/20 Last Quarter Moon occurs at 13:39

9/21 The Curtiss Cross, an X-shaped illumination effect located between the craters Parry and Gambart, is predicted to occur at 3:40

9/23 Mars is 5 degrees north of the Moon at 8:00; the autumnal equinox occurs in the northern hemisphere at 9:05

9/26 Uranus (apparent size 3.7", magnitude 5.7) is at opposition at 0:00

9/27 New Moon (lunation 1098) occurs at 11:09

9/28 The Moon is at perigee, subtending 33 arc minutes from a distance of 357,557 kilometers (221,176 miles), at 1:00; Venus is 6 degrees north of the Moon at 10:00; Saturn is 7 degrees north of the Moon at 14:00; Mercury is in superior conjunction at 20:00

9/29 Venus is 1.3 degrees south of Saturn at 23:00

The zodiacal light, or the false dawn, is visible about two hours before sunrise from a dark site during the latter part of September.

The Moon is 3.3 days old and is located in Virgo on September 1 at 0:00 UT. On the evening of September 3, the Moon occults Delta Scorpii (magnitude 2.3), the brightest star to undergo a lunar occultation this year. This event is visible from the southern and eastern United States, the Caribbean, Central America, and the northern tip of South America. Browse Watch a Star Wink Out on September 3rd - Observing Highlights - SkyandTelescope.com and Web Page Redirection for IOTA for additional information. The Moon is at its greatest northern declination (+23.1 degrees) on September 19 and its greatest southern declination (-23.1 degrees) on September 5. Longitudinal libration is at a maximum of +6.6 degrees on September 6 and a minimum of -7.6 degrees on September 22. Latitudinal libration is at a maximum of +6.6 degrees on September 26 and a minimum of -6.6 degrees on September 12. Visit Saber Does The Stars saberdoesthestars for tips on spotting extreme crescent Moons. Times and dates for the lunar light rays predicted to occur this month are available at Lunar Sunrise/Sunset Crater Rays

The Sun is located in Leo on September 1. It crosses the celestial equator from north to south on September 23, the date of the autumnal equinox.

Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on September 1: Mercury (magnitude 0.1, 7.8", 35% illuminated, 0.86 a.u., Leo), Venus (magnitude -3.9, 9.7", 100% illuminated, 1.72 a.u., Leo), Mars (magnitude 1.4, 4.7", 93% illuminated, 1.99 a.u., Gemini), Jupiter (magnitude -2.7, 44.8", 99% illuminated, 4.40 a.u., Aries), Saturn (0.9 magnitude, 15.9", 100% illuminated, 10.44 a.u., Virgo), Uranus (5.7 magnitude, 3.7", 100% illuminated, 19.16 a.u., Pisces), Neptune (7.8 magnitude, 2.3", 100% illuminated, 29.01 a.u., Aquarius), and Pluto (14.1 magnitude, 0.1", 100% illuminated, 31.62 a.u., Sagittarius).

This month Venus and Saturn are located in the west, Uranus in the east, and Neptune in the southeast during the evening. (Venus is visible only at the end of September.) At midnight, Jupiter can be found in the east, Uranus in the southeast, and Neptune in the south. Mercury and Mars are in the east, Jupiter in the southwest, and Uranus in the west in the morning sky.

At midmonth, Mercury is visible during morning twilight, Mars rises at 2:00 p.m. EDT, Jupiter rises at 9:00 p.m. EDT and transits the meridian at 4:00 a.m. EDT, and Saturn sets at 8:00 p.m. EDT for observers at latitude 40 degrees north.

During September, Mercury increases markedly in brightness, while growing in illumination and shrinking in apparent size. The speedy planet reaches greatest western elongation on September 3. It is at perihelion five days later. Mercury is in superior conjunction on September 28.

Venus is too close to the Sun to be seen until the very end of the month. It’s less than two degrees below Saturn on September 29 but both planets are too close to the horizon to be readily visible from the northern hemisphere.

Mars departs Gemini and enters Cancer on September 15. It is only 5.1 arc seconds in apparent size at month’s end.

Jupiter increases in apparent size by more than three arc seconds this month. Ganymede is eclipsed by Jupiter from 11:29 p.m. EDT to 1:33 a.m. EDT on the night of September 14 and the morning of September 15. The Galilean satellite is then occulted by the planet from 4:01 a.m. EDT to 5:16 a.m. EDT. E. E. Barnard discovered Jupiter’s fifth satellite, fourteenth-magnitude Amalthea, using the 36-inch refractor at the Lick Observatory on September 9, 1892. Browse Transit Times of Jupiter's Great Red Spot - Planets - SkyandTelescope.com to determine transits of the central meridian by the Great Red Spot. Data on the Galilean satellites is available at Jupiter's Moons Javascript Utility - Interactive Observing Tools - SkyandTelescope.com

Saturn disappears into the glare of the Sun during September. On September 19, 1848, William Bond discovered Saturn’s fourteenth-magnitude satellite Hyperion, the first irregular moon to be discovered.

Uranus is located almost exactly 15 degrees due south of the third-magnitude star Algenib (Gamma Pegasi). It shines at magnitude 5.7 when it reaches opposition on the evening of September 25 and can be seen without optical aid from a dark site. At that time, Uranus is 0.3 degree north of the celestial equator and approximately 2.6 light hours or 1.77 billion miles from the Earth.

During the first week of the month, Neptune, the fourth-magnitude star Iota Aquarii, and the fifth-magnitude star 38 Aquarii form an isosceles triangle. The pattern changes as the planet’s retrograde motion carries the planet to the west. Neptune was discovered by Johann Gottfried Galle on September 23, 1846, using Urbain Le Verrier’s calculations of its position.

Finder charts for Uranus and Neptune appear on page 53 of the September 2011 issue of Sky & Telescope and are posted online at http://media.skyandtelescope.com/documents/Uranus-Neptune-2011.pdf

Pluto’s westward motion ends as the second half of September begins. The dwarf planet culminates just after nightfall. A finder chart is available on pages 64 and 65 of the July 2011 issue of Sky & Telescope.

For more on the planets and how to locate them, browse The Naked Eye Planets in the Night Sky (and how to identify them)

Comet C/2009 P1 (Garradd) shines at seventh-magnitude as it heads westward through Vulpecula and into southeastern Hercules this month. The comet passes south of Collinder 399 (the Coathanger) on the evenings of September 2 and 3. Browse Comet Chasing and Visual Comets in the Future (Northern Hemisphere) for additional information on comets that are visible this month.

Asteroid 4 Vesta spends the entire month approximately one degree southwest of the fourth-magnitude star Psi Capricorni. The minor planet decreases in brightness to magnitude 6.9 by the end of September. Karl Harding discovered asteroid 3 Juno on September 1, 1804. Information on asteroid occultations of stars can be found at Global Asteroid Events

A free star map for September can be downloaded at Skymaps.com - Publication Quality Sky Maps & Star Charts

Eighty binary and multiple stars for September: 12 Aquarii, Struve 2809, Struve 2838 (Aquarius); Alpha Capricorni, Sigma Capricorni, Nu Capricorni, Beta Capricorni, Pi Capricorni, Rho Capricorni, Omicron Capricorni, h2973, h2975, Struve 2699, h2995, 24 Capricorni, Xi Capricorni, Epsilon Capricorni, 41 Capricorni, h3065 (Capricornus); Kappa Cephei, Struve 2751, Beta Cephei, Struve 2816, Struve 2819, Struve 2836, Otto Struve 451, Struve 2840, Struve 2873 (Cepheus); Otto Struve 394, 26 Cygni, h1470, h1471, Omicron Cygni, Struve 2657, 29 Cygni, 49 Cygni, 52 Cygni, 59 Cygni, 60 Cygni, 61 Cygni, Struve 2762 (Cygnus); Struve 2665, Struve 2673, Struve 2679, Kappa Delphini, Struve 2715, Struve 2718, Struve 2721, Struve 2722, Struve 2725 (in the same field as Gamma Delphini), Gamma Delphini, 13 Delphini, Struve 2730, 16 Delphini, Struve 2735, Struve 2736, Struve 2738 (Delphinus); 65 Draconis, Struve 2640 (Draco); Epsilon Equulei, Lambda Equulei, Struve 2765, Struve 2786, Struve 2793 (Equuleus); 1 Pegasi, Struve 2797, h1647, Struve 2804, Struve 3112, 3 Pegasi, 4 Pegasi, Kappa Pegasi, h947, Struve 2841, Struve 2848 (Pegasus); h1462, Struve 2653, Burnham 441, Struve 2655, Struve 2769 (Vulpecula)

Challenge binary star for September: 1 Delphini

Notable carbon star for September: LW Cygni

Forty-five deep-sky objects for September: M2, M72, M73, NGC 7009 (Aquarius); M30, NGC 6903, NGC 6907 (Capricornus); B150, B169, B170, IC 1396, NGC 6939, NGC 4343, B361, Ba6, Be87, Cr 421, Do9, IC 1369, IC 4996, IC 1516, LDN 906, M29, M39, NGC 6866, NGC 6871, NGC 6888, NGC 6894, NGC 6910, NGC 6960, NGC 6992, NGC 7000, NGC 7008, NGC 7026, NGC 7027, NGC 7039, NGC 7063, NGC 7086 (Cygnus); NGC 6891, NGC 6905, NGC 6934, NGC 7006 (Delphinus); NGC 7015 (Equuleus); M15 (Pegasus); NGC 6940 (Vulpecula)

Top ten binocular deep-sky objects for September: IC 1396, LDN 906, M2, M15, M29, M30, M39, NGC 6939, NGC 6871, NGC 7000

Top ten deep-sky objects for September: IC 1396, M2, M15, M30, NGC 6888, NGC 6946, NGC 6960, NGC 6992, NGC 7000, NGC 7009

Challenge deep-sky object for September: Abell 78 (Cygnus)

The objects listed above are located between 20:00 and 22:00 hours of right ascension.

[RikM]

Wow, what a comprehensive observing guide for the month. When the weather improves, I will have a go at some of the objects listed. Thanks very much for posting.