October 2010 Celestial Calendar & Observing Notes c/o Dave Mitsky

[Big Dipper]

October 2010 Celestial Calendar & Observing Notes courtesy of Dave Mitsky (calendar data also reproduced in our forum calendar).

All times, unless otherwise noted, are UT.

10/1 Mercury is at its greatest heliocentric latitude north today; Saturn is in conjunction with the Sun at 1:00; Last Quarter Moon occurs at 3:52; the Curtiss Cross, an X-shaped illumination effect located between the craters Parry and Gambart, is predicted to occur at 18:54

10/6 The Moon is at perigee, subtending 33'35" from a distance of 359,455 kilometers (223,354 miles), at 13:38

10/7 New Moon (lunation 1086) occurs at 18:44; Venus is stationary at 19:00

10/8 The peak of the Draconid or Giacobinid meteor shower (10 to 30 per hour) occurs at 13:00

10/9 Venus is 3 degrees south of the Moon at 19:00

10/10 Mars is 4 degrees north of the Moon at 2:00

10/14 First Quarter Moon occurs at 21:27

10/15 the Lunar X, also known as 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 3:41

10/17 Mercury is in superior conjunction at 1:00; Neptune is 5 degrees south of the Moon at 22:00

10/18 The Moon is at apogee, subtending 29'21" from a distance of 405,428 kilometers (251,921 miles), at 18:17

10/20 Jupiter is 7 degrees south of the Moon at 11:00; Uranus is 6 degrees south of the Moon at 15:00; Comet 103P/Hartley is closest to the Earth (0.121 a.u.) at 17:00

10/21 The peak of the Orionid meteor shower (normally 10 to 20 per hour) occurs at 16:00

10/23 Full Moon, known as the Blood Moon and this year’s Hunter’s Moon, occurs at 1:36

10/24 A double Galilean satellite shadow transit (Europa’s shadow follows Ganymede’s) begins at 1:41

10/25 Mercury is at the descending node today; the Moon is 1.2 degrees south of the bright open cluster M45 (the Pleiades) in Taurus at 11:00

10/27 The Moon is 0.7 degree north of the bright open cluster M35 in Gemini at 23:00

10/29 Venus is in inferior conjunction at 1:00

10/30 Last Quarter Moon occurs at 12:46

10/31 A double Galilean satellite shadow transit (Europa’s shadow follows Ganymede’s) begins at 4:17; the Curtiss Cross, an X-shaped illumination effect located between the craters Parry and Gambart, is predicted to occur at 8:00

Ejnar Hertzsprung and Henry Norris Russell were born this month.

The Orionid meteor shower peaks during the morning of October 21 but is compromised by strong moonlight.

During the second half of the month, the zodiacal light may be visible in the pre-dawn eastern sky from a dark site.

The Moon is 22.6 days old and is located in Gemini on October 1 at 0:00 UT. The Moon reaches its greatest northern declination on October 26 (+24.3 degrees) and its greatest southern declination on October 12 (-24.5 degrees). Longitudinal libration is at a maximum of +7.5 degrees on October 12 and a minimum of -5.4 degrees on October 27. Latitudinal libration is at a maximum of +6.6 degrees on October 7 and a minimum of -6.6 degrees on October 21. The Moon occults Omicron Leonis (magnitude 3.5) on the morning of October 4. See Bright Star Occultation and 1024 H for information on this event and Web Page Redirection for IOTA for information on other lunar occultations. Visit Extreme Lunar Crescent Data [L1086-90] | Saber Does The Stars 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 Virgo on October 1 at 0:00 UT.

Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on October 1: Mercury (-1.1 magnitude, 5.5", 88% illuminated, 1.23 a.u., Virgo), Venus (-4.8 magnitude, 44.5", 19% illuminated, 0.38 a.u., Libra), Mars (1.5 magnitude, 4.1", 97% illuminated, 2.26 a.u., Libra), Jupiter (-2.9 magnitude, 49.7", 100% illuminated, 3.97 a.u., Pisces), Saturn (0.9 magnitude, 15.7", 100% illuminated, 10.56 a.u., Virgo), Uranus (5.7 magnitude, 3.7", 100% illuminated, 19.10 a.u., Pisces), Neptune (7.9 magnitude, 2.3", 100% illuminated, 29.26 a.u., Capricornus), and Pluto (14.0 magnitude, 0.1", 100% illuminated, 31.98 a.u., Sagittarius).

During October evenings, Venus and Mars lie in the southwest and Jupiter, Uranus, and Neptune in the southeast. At midnight, Jupiter and Uranus are located in the south and Neptune in the southwest. Mercury and Saturn are in the east in the morning sky.

At midmonth, Venus sets at 7:00 p.m. EDT, Mars sets at 8:00 p.m. EDT, Jupiter and Uranus transit at 11:00 p.m. EDT and set at 5:00 a.m. EDT for observers at latitude 40 degrees north.

Mercury is visible in the morning sky during early October. It is in superior conjunction on October 17.

As the month progresses, Venus becomes increasingly difficult to see. Venus lies to the lower right and Mars to the upper right of a thin crescent Moon on the evening of October 9. The planet subtends 51 arc minutes and is illuminated just 11% on that date. Venus passes between the Earth and the Sun on October 28.

Mars is 6 degrees to the upper right of Venus on October 1. The Red Planet exits Libra and enters Scorpius near the end of October, at which time it is lost in the glare of the Sun.

Jupiter retains its prominence throughout the month, shining at magnitude -2.9 on October 1 and magnitude -2.8 on October 31, and subtending 49.7 arc seconds on October 1 and 47.1 arc seconds on October 31. The King of the Planets is in retrograde near the border of Aquarius and Pisces. It enters Aquarius in mid-October. Two double Galilean satellite events occur this month. Click on SkyandTelescope.com - Planets - Transit Times of Jupiter's Great Red Spot to determine transits of the central meridian by the Great Red Spot. Data on the Galilean satellites is available at SkyandTelescope.com - Interactive Observing Tools - Jupiter's Moons Javascript Utility

Saturn is in conjunction with the Sun on October 1 but returns to the morning sky near the end of October.

Uranus is 1.4 degrees northeast of Jupiter on October1. This distance increases to 3.2 degrees by October 31.

This month Neptune is located approximately 3 degrees northeast of the third-magnitude star Delta Capricorni and very close to the fifth-magnitude star Mu Capricorni. Neptune passes 0.2 degree north of Mu Capricorni on October 14.

Finder charts for Uranus and Neptune are posted at http://media.skyandtelescope.com/documents/Uranus_Neptune_2010.pdf

The dwarf planet Pluto is visible just after nightfall, during the first week of the month. A finder chart is available on page 60 of the July 2010 issue of Sky & Telescope and online at SkyandTelescope.com - SkyTel Beyond the Page - See Pluto in 2010

Asteroid 6 Hebe continues to trek southwestward through Cetus this month. In early October, the eighth-magnitude minor planet is located about two degrees south of the fourth-magnitude star 7 Ceti. Asteroid 1212 Francette occults an 8.8-magnitude star in Gemini on the morning of October 14. On the evening of October 16, asteroid 1273 Helma occults an 8.0-magnitude star in Pisces. The occultations are visible along narrow paths running from southern California to South Carolina and from Labrador to western Texas respectively. For additional information on these events, browse Asteroid Occultation Predictions (Current)

Comet 103P/Hartley (Comet Hartley 2) heads southeastward from Cassiopeia into Gemini during the course of October. On October 1, this periodic comet lies 1.5 degrees south of the second-magnitude star Schedar (Alpha Cassiopeiae). It passes less than one degree to the south of the Double Cluster (NGC 869 and NGC 884) in Perseus on the night of October 7 and a couple of degrees to the south of the first-magnitude star Capella (Alpha Aurigae) on October 19. Comet Hartley 2 makes its closest approach to the Earth (0.121 a.u.) on October 20. On October 28, the orientation of the comet’s dust tail tilts to edge-on, as 103/Hartley travels through Gemini. The comet also reaches perihelion (1.06 a.u.) on that day. Finder charts can be found at http://www.astronomy.com/asy/objects/images/october-2010-comet-finder-c.jpg and SkyandTelescope.com - Homepage Observing - Encounters with Comet Hartley 2 and on pages 56 and 57 of the October 2010 issue of Sky & Telescope. An ephemeris is posted at http://scully.cfa.harvard.edu/~cgi/ReturnPrepEph?d=c&o=0103P

The famous eclipsing variable star Algol (Beta Persei) is at a minimum, decreasing in magnitude from 2.1 to 3.4, on October 1, 4, 6, 9, 12, 15, 18, 21, 24, and 27. Consult SkyandTelescope.com - Variable Stars - The Minima of Algol for the times of the eclipses. For more on Algol, see Algol and Algol / Beta Persei 3

The famous pulsating variable star Mira (Omicron Ceti), the Wonderful, brightens during October, reaching maximum magnitude near the end of the month. Click on Mira, Omicron Ceti for further information on Mira.