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Big Dipper

April 2014 Celestial Calendar c/o Dave Mitsky

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April 2014 Celestial Calendar & Observing Notes c/o Dave Mitsky
(calendar data also reproduced in our forum calendar ).

All times unless otherwise noted are UT.

4/1 Jupiter is at eastern quadrature today
4/2 Uranus is in conjunction with the Sun at 7:00
4/4 The moon is 2 degrees north of the first-magnitude star Aldebaran (Alpha Tauri) at 7:00
4/6 Jupiter is 5 degrees north of the Moon at 23:00
4/7 The Lunar X (also known as the Werner or Purbach Cross), an X-shaped illumination effect involving various rims and ridges between the craters La Caille, Blanchinus, and Purbach, is predicted to begin at 8:28; First Quarter Moon occurs at 8:31
4/8 The Moon is at apogee, subtending 29'32'' from a distance of 404,500 kilometers (251,344 miles), at 15:00; Mars is at opposition (magnitude -1.48, apparent size 15.16") at 21:00
4/9 Mercury is at its greatest heliocentric latitude south today
4/11 Venus is at the descending node today; asteroid 3 Juno is in conjunction with the Sun at 7:00
4/12 Venus is 0.7 degree north of Neptune at 8:00
4/13 Asteroid 4 Vesta (magnitude 5.8) is at opposition at 12:00
4/14 Mars is at closest approach (92.4 million kilometers or 57.4 million miles distant) at 13:00; Mars is 3 degrees north of the Moon at 18:00
4/15 Pluto is stationary at 1:00; the Moon is 1.7 degrees north of the first-magnitude star Spica (Alpha Virginis) at 4:00; asteroid 1 Ceres (magnitude 7.0) is at opposition at 6:00; Full Moon, known as the Egg or Grass Moon, occurs at 7:42; a total lunar eclipse visible from the western hemisphere reaches its maximum at 7:45
4/17 Saturn is 0.4 degree north of the Moon, with an occultation occurring in southern South America and French Polynesia, at 7:00
4/22 Last Quarter Moon occurs at 7:52; the peak of the Lyrid meteor shower (20 per hour) occurs at 17:00
4/23 The Curtiss Cross, an X-shaped illumination effect located between the craters Parry and Gambart, is predicted to begin at 10:01; the Moon is at perigee, subtending 32'19'' from a distance of 369,765 kilometers (229,762 miles), at 20:00
4/24 Neptune is 5 degrees south of the Moon at 22:00
4/26 Mercury is in superior conjunction at 3:00
4/27 Uranus is 2 degrees south of the Moon at 11:00
4/28 Mercury is at the ascending node today
4/29 A rare non-central annular solar eclipse begins in eastern Antarctica at 5:57; New Moon (lunation 1130) occurs at 6:14

Christiaan Huygens (1629-1695) was born this month.

The first photograph of the Sun was taken on April 2, 1845. The Hubble Space Telescope was placed in orbit on April 25, 1990. The Compton Gamma Ray Observatory achieved orbit on April 7, 1991.

The Lyrid meteor shower peaks on the morning of April 22nd. A typical zenithal hourly rate is about 20 meteors per hour but short outbursts have occurred occasionally.

Information on Iridium flares and passes of the ISS, the Tiangong-1, the USAF’s X-37B, the HST, and other satellites can be found at http://www.heavens-above.com/

The Moon is 1.2 days old and is located in Pisces at 0:00 UT on April 1st. It's at its greatest northern declination of +19.0 degrees on April 5th and its greatest southern declination of -18.9 degrees on April 19th. Latitudinal libration is at a maximum of +6.9 degrees on April 8th and a minimum of -6.8 degrees on April 22nd. Longitudinal libration is at a maximum of +5.6 degrees on April 2nd and +4.8 degrees on April 29th and a minimum of -5.2 degrees on April 15th. A 20% illuminated waxing crescent Moon occults some of the stars in the Hyades open star cluster (Melotte 25) for North American observers on the night of April 3rd (April 4th UT). The brightest stars being occulted will be Delta 1 Tauri (magnitude +3.8), Delta 2 Tauri (magnitude +4.8), and Delta 3 Tauri (magnitude +4.3). Consult http://www.lunar-occultations.com/iota/bstar/bstar.htm or pages 50 and 51 of the April issue of Sky & Telescope for more on the occultation. A total lunar eclipse that’s visible throughout the western hemisphere begins at 12:54 a.m. EDT and ends at 6:39 a.m. EDT on April 15th. Partial eclipse starts at 1:58:19 a.m. EDT and ends at 5:33:04 a.m. EDT. Totality begins at 3:06:47 a.m. EDT (7:06:47 UT) and lasts for 78 minutes, with mid-eclipse occurring at 3:45:40 a.m. EDT. Articles on the eclipse appear on pages 52 through 54 of the April issue of Astronomy and on pages 60 and 61 of the April issue of Sky & Telescope. Click on http://www.astronomy.com/observing/sky-events/2014/02/watch-a-total-lunar-ecl... and http://www.skyandtelescope.com/observing/highlights/April-2014-Total-Lunar-Ec... for further information on the eclipse, the first of four consecutive total lunar eclipses - an eclipse tetrad - taking place in 2014 and 2015. Visit http://saberdoesthestars.wordpress.com/2011/07/05/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 http://www.lunar-occultations.com/rlo/rays/rays.htm

The Sun is located in Pisces on April 1. An uncommon non-central annular eclipse, the 21st eclipse of Saros 148, takes place in eastern Antarctica on April 29th. A partial eclipse is visible from Australia, southern Indonesia, and the southern Indian Ocean. Observers in southern Australia can see a 60% eclipsed Sun and Tasmanians a Sun that is 70% covered by the Moon. Greatest eclipse occurs at 6:03:25 UT.

Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on April 1: Mercury (-0.2 magnitude, 5.8", 77% illuminated, 1.17 a.u., Aquarius), Venus (-4.4, 22.2", 54% illuminated, 0.75 a.u., Capricornus), Mars (-1.3 magnitude, 14.7", 100% illuminated, 0.64 a.u., Virgo), Jupiter (-2.2 magnitude, 38.5", 99% illuminated, 5.12 a.u., Gemini), Saturn (+0.3 magnitude, 18.2", 100% illuminated, 9.13 a.u., Libra), Uranus (+5.9 magnitude, 3.4", 100% illuminated, 21.00 a.u. on April 16th, Pisces), Neptune (+7.9 magnitude, 2.2", 100% illuminated, 30.62 a.u. on April 16th, Aquarius), and Pluto (+14.1 magnitude, 0.1", 100% illuminated, 32.41 a.u. on April 16th, Sagittarius).

Mars is located in the southeast and Jupiter in the west in the evening. At midnight, Mars is in the south, Jupiter is in the west, and Saturn is in the southeast. Mercury, Venus, Uranus, and Neptune are in the east. Mars can be found in the west, Saturn in the southwest, and Uranus and Neptune in the east in the morning sky.

Mercury disappears from view by the middle of April and reaches superior conjunction on April 26th.

Venus is positioned low in the east at dawn. It rises about two hours before sunrise in early April. The planet dims in magnitude from -4.4 to -4.2 and decreases in apparent size from 22 to 17 arc seconds, while increasing in illumination from 54 to 66% during April. Venus occults the fourth-magnitude star Lambda Aquarii, an event visible only from scattered sites in the South Pacific, on April 16th.

Mars culminates around 2:00 a.m. local time on April 1st and around 11:00 p.m. local time at month’s end. The apparent diameter of Mars exceeds 15 arc seconds on April 6th and drops below 15 arc seconds on April 22nd. Mars is at opposition at 21:00 UT on April 8th and is closest to our planet at 13:00 UT on April 14th. On that date, it is 92,390,000 kilometers, 0.61756 astronomical units, or 5.1 light minutes from the Earth and is situated five degrees south of the celestial equator. The "bland" desert side of Mars faces the Earth on April 1st. Mare Cimmerium is the most noticeable dark surface feature in the south and Utopia in the north. The North Polar Cap (NCP) is quite small, since it is currently summer in the Martian northern hemisphere. The SPC is facing away from the Earth, during this apparition of Mars. Unfortunately, dark features won’t be visible again until midnight on April 15th, when Mare Erythraeum and Aurorae Sinus in the south and Acidalia Planitia in the far north can be detected. On April 21st, Acidalia Planitia is near the central meridian (CM) of the planet during the later evening and Sinus Sabaeus is east of the CM. During the final week of April, triangular-shaped Syrtis Major, the most prominent Martian feature, makes its debut. Syrtis Major lies on the CM on April 30th. As demonstrated by the images at http://www.universetoday.com/110279/till-hellas-freezes-over-see-frost-and-cl..., a cloud-covered or frosted-over Hellas Planitia, which lies to the south of Syrtis Major, can easily be mistaken for the SPC. Martian surface features, clouds, and limb haze can be greatly enhanced through the use of various color or dielectric filters. My favorite color filters are the Wratten #21 (orange), Wratten #30 (magenta), and Wratten #80A (light blue). Browse http://alpo-astronomy.org/mars/articles/FILTERS1.HTM for information on color filters. Sky & Telescope’s Mars Profiler - http://www.skyandtelescope.com/observing/objects/javascript/3307831.html - is a very handy way to determine which surface features are visible at a given time and date. Click on http://planetary.s3.amazonaws.com/assets/images/4-mars/2014/20140303_Mars_Vik... for an incredible new version of the Viking Orbiter global color map of Mars and http://d1jqu7g1y74ds1.cloudfront.net/wp-content/uploads/2014/03/Mars-map-ALPO... for a map of Mars produced by the A.L.P.O. See http://www.curtrenz.com/mars and http://www.nakedeyeplanets.com/mars-oppositions.htm for more on the 2014 apparition of the Red Planet.

As April begins, Jupiter sets not long after 2:00 a.m. local time. The giant planet is 90 degrees east of the Sun on April 1st. Jupiter shrinks in apparent diameter from 38 to 35 arc seconds and dims from magnitude -2.2 to magnitude -2.0 during the course of the month. As April ends, Jupiter is situated between the fifth-magnitude star Omega Geminorum and the fourth-magnitude star Zeta Geminorum. Not long after 11:00 p.m. EDT on the evening of April 21st, Io, Europa, and Callisto are arrayed in a line almost perpendicular to Jupiter’s equator. (At the same time, a shadow transit by Europa and a transit by the Great Red Spot are underway.) This unusual alignment lasts no longer than 15 minutes, however. Browse http://skyandtelescope.com/observing/objects/planets/article_107_1.asp in order to determine transit times of Jupiter’s central meridian by the Great Red Spot. That information is also displayed on page 52 of the April issue of Sky & Telescope. Data on the Galilean satellite events is available at http://skytonight.com/observing/objects/javascript/3307071.html#

The north side of Saturn’s ring plane is tilted almost 22 degrees with respect to the Earth this month. The planet shines at magnitude +0.1 and its rings span 42 arc seconds. On the morning of April 18th, the waning gibbous Moon passes 0.4 degree south of the Ringed Planet. An occultation - http://www.lunar-occultations.com/iota/planets/0417saturn.htm - takes place in the southern hemisphere. Saturn’s unusual moon Iapetus, which varies in brightness from magnitude 10.1 to magnitude 11.9, reaches its farthest distance west of the planet - nine arc minutes - at the middle of the month. At that time, Iapetus shines at tenth magnitude. For further information on Saturn’s satellites, browse http://www.skyandtelescope.com/observing/objects/javascript/3308506.html

Uranus is not observable from the northern hemisphere this month.

Neptune lies in the east at dawn. Venus (magnitude -4.3) passes less than one degree north of Neptune (magnitude +7.9) on the morning of April 12th. Southern hemisphere observers will have a more favorable view of this event.

The dwarf planet Pluto is fairly high in the sky in northwestern Sagittarius during morning twilight.

For more on the planets and how to locate them, browse http://www.nakedeyeplanets.com/

Asteroid 4 Vesta (magnitude 5.8) is at opposition on April 13th. Two days later asteroid 1 Ceres (magnitude 7.0) reaches opposition. Both asteroids are heading north-westward through Virgo. See http://media.skyandtelescope.com/documents/Web_Ceres_Vesta_2014.pdf for a finder chart. Asteroid 2 Pallas shines at eighth magnitude as it glides north-eastward through Hydra and into southwestern Leo this month. It passes south of the Mira-type variable star R Leonis, which ranges in brightness from fourth to eleventh magnitude, on April 25th. Additional current information on asteroids can be found at http://www.curtrenz.com/asteroids and asteroidal ephemerides at http://www.minorplanetcenter.net/iau/Ephemerides/Bright/2014/index.html

Comet C/2012K1 (PANSTARRS) travels north-westward through Corona Borealis and Bootes and into Ursa Major. The ninth-magnitude comet begins April in the vicinity of the globular star cluster M13 in Hercules, passes north of the fourth-magnitude star Lambda Bootis on April 24th and south of the second-magnitude star Eta Ursae Majoris on April 29th, and ends the month near the fifth-magnitude star 24 Ursae Majoris, northeast of the spiral galaxy M51 in Canes Venatici. Visit http://scully.cfa.harvard.edu/cgi-bin/returnprepeph.cgi?d=c&o=CK12K010 for an ephemeris and http://cometchasing.skyhound.com/ for additional information on this comet and others visible this month.

A wealth of current information on solar system celestial bodies is posted at http://www.curtrenz.com/astronomical

Browse http://astrocast.tv/ for an informative video on astronomical events taking place this month.

A free star map for April can be downloaded at http://www.skymaps.com/downloads.html and http://www.telescope.com/content.jsp?pageName=Monthly-Star-Chart

The famous eclipsing variable star Algol (Beta Persei) is at a minimum, decreasing in magnitude from 2.1 to 3.4, on April 2nd, 4th, 7th, 10th, 13th, 16th, 19th, 22nd, 24th, 27th, and 30th. For more on Algol, see http://stars.astro.illinois.edu/sow/Algol.html and http://www.solstation.com/stars2/algol3.htm

Seventy-five binary and multiple stars for April: h4481 (Corvus); Aitken 1774, Gamma Crateris, Jacob 16, Struve 3072, h4456, Burnham 1078 (Crater); h4311, Burnham 219, N Hydrae, h4455, h4465 (Hydra); 31 Leonis, Alpha Leonis (Regulus), h2520, Struve 1417, 39 Leonis, Struve 1421, Gamma Leonis (Algieba), Otto Struve 216, 45 Leonis, Struve 1442, Struve 1447, 49 Leonis, Struve 1482, 54 Leonis, Struve 1506, Chi Leonis, 65 Leonis, Struve 1521, Struve 1527, Struve 1529, Iota Leonis, 81 Leonis, 83 Leonis, Tau Leonis, 88 Leonis, 90 Leonis, Struve 1565, Struve 1566, 93 Leonis, h1201, S Leonis (Leo); h2517, Struve 1405, Struve 1432, 33 Leo Minoris, Struve 1459, 40 Leo Minoris, Struve 1492 (Leo Minor); Struve 1401, Struve 1441, Struve 1456, Struve 1464, 35 Sextantis, 40 Sextantis, 41 Sextantis (Sextans); Struve 1402, Struve 1415, Struve 1427, Struve 1462, Struve 1486, Struve 1495, Struve 1510, Struve 1520, Xi Ursae Majoris, Nu Ursae Majoris, Struve 1541, 57 Ursae Majoris, Struve 1544, Struve 1553, Struve 1561, Struve 1563, 65 Ursae Majoris, Otto Struve 241 (Ursa Major)

Notable carbon star for April: V Hydrae (Hydra)

One hundred deep-sky objects for April: NGC 4024, NGC 4027 (Corvus); NGC 3511, NGC 3513, NGC 3672, NGC 3887, NGC 3892, NGC 3955, NGC 3962, NGC 3981 (Crater); NGC 3091, NGC 3109, NGC 3145, NGC 3203, NGC 3242, NGC 3309, NGC 3585, NGC 3621, NGC 3717, NGC 3904, NGC 3936 (Hydra); M65, M66, M95, M96, M105, NGC 3098, NGC 3162, NGC 3177, NGC 3185, NGC 3190, NGC 3226, NGC 3227, NGC 3300, NGC 3346, NGC 3367, NGC 3377, NGC 3384, NGC 3389, NGC 3412, NGC 3437, NGC 3489, NGC 3495, NGC 3507, NGC 3521, NGC 3593, NGC 3607, NGC 3608, NGC 3626, NGC 3628, NGC 3630, NGC 3640, NGC 3646, NGC 3655, NGC 3681, NGC 3684, NGC 3686, NGC 3691, NGC 3810, NGC 3842, NGC 3872, NGC 3900, NGC 4008 (Leo); NGC 3245, NGC 3254, NGC 3277, NGC 3294, NGC 3344, NGC 3414, NGC 3432, NGC 3486, NGC 3504 (Leo Minor); NGC 2990, NGC 3044, NGC 3055, NGC 3115, NGC 3156, NGC 3166, NGC 3169, NGC 3246, NGC 3423 (Sextans); IC 750, M97, M108, M109, NGC 3079, NGC 3184, NGC 3198, NGC 3310, NGC 3359, NGC 3610, NGC 3665, NGC 3675, NGC 3738, NGC 3877, NGC 3898, NGC 3941, NGC 3953, NGC 3998, NGC 4026 (Ursa Major)

Top ten deep-sky objects for April: M65, M66, M95, M96, M97, M105, M108, NGC 3115, NGC 3242, NGC 3628

Top ten binocular deep-sky objects for April: M65, M66, M95, M96, M97, M105, M108, M109, NGC 3115, NGC 3242

Challenge deep-sky object for April: Leo I (Leo)

The objects listed above are located between 10:00 and 12:00 hours of right ascension.

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