San Diego Astronomy Association Celebrating Over 40 Years of Astronomical Outreach Office (619) 645-8940 April 2005 Observatory (619) 766-9118 http://www.sdaa.org Messier Marathon A Non-Profit Educational Association By Ed Rumsey P.O. Box 23215, San Diego, CA 92193-3215 The club’s Messier Marathon was held the evening of March 12/13 at TDS. Both SDAA Business Meeting of the public pads were filled to capacity early making for tremendous interaction Next meeting will be held at: with fellow astronomers. A seasonal marine layer ensured a reduced San Diego SKF Condition Monitoring light dome for the coming evening. Friday night had been a bit dewy but clear 5271 Viewridge Court through out the evening and we were hopeful for at least the same. Some even San Diego, CA 92123 had visions of a repeat of last year with its warm dry clear skies. While observing April 12th at 7:30pm all 110 objects was unlikely, ambitions were high. With the setting of the sun, a warm afternoon breeze subsided and planets popped Next Program Meeting first into view upon a cloudless sky. Mercury at 15° above the horizon made a April 20th 7:00 pm wonderful crescent while Saturn displayed magnificent ring structure with a hint of Mission Trails Regional Park banding. A 65-hour old moon wetted the astronomers’ appetites with splendid views Visitor and Interpretive Center of the terminator and lunar structure. A hint of the evening’s moisture was visible to 1 Father Junipero Serra Trail the west in the valley below. Dew was going to be an issue this evening. Messier Continued on page 3 The Urban Astronomer CONTENTS Despite all the rain and clouds we had this month, we start our urban observing April 2005 Vol XLI, Issue 04 session just as the Sun sets and twilight begins to fill the sky. Mercury, the smallest Published Monthly by the and most elusive of the visible planets shines at nearly 0 magnitude and lies some 10- San Diego Astronomy Association 12 degrees above the western horizon. Although not visible by the time the newslet- 75¢ /$8.00 year ter arrives in the mail, this tiny world is still very much worth mentioning. Currently Incorporated in California in 1963 at eastern elongation, being visible in the western sky at sunset, Mercury at 166x reveals itself as almost a half disk as it dances in the atmospheric turbulence. Messier Marathon..........................................1 Mercury is best viewed during western elongation, rising just before dawn, and The Urban Astronomer.............................1 before the Sun can heat-up the atmosphere. Even though no surface detail is visible, Astronomy 101............................................2 just the aspect of hunting down this small rocky planet can be rewarding, and I Calendar .....................................................4 never pass up a chance to place Mercury into my crosshairs. AISIG ..............................................................5 Sky Watch.......................................................6 From Mercury we travel back to the southern sky in pursuit of M-93, an Open Astronomy Crossword..................................7 Cluster in the vaguely defined constellation Puppis, the Stern. Puppis is part of the Treasurer’s Report.......................................8 old constellation Argo Navis, the ship of the Argonauts, and is only partially visible Board Minutes ..............................................8 from our location in the Northern Hemisphere. To locate M-93, I actually start at NASA Space Place.....................................9 Delta Canis Majoris, then proceed 8 degrees eastward to the very dim, 3rd magnitude The Back Page...........................................10 yellow double star, Xi Puppis. Within the finder, Xi appears at a moderate separa- tion. From Xi, proceed 2 degrees to the 7 o’clock position as seen in the finder Urban Continued on page 5 SanSan DiegoDiego AstronomyAstronomy AssociationAssociation By Scott Baker Air Telescope? Is that anything like an Air Guitar? The constellation of Sextans Uraniae, the “Heavenly Sextant” is another creation of the Polish astronomer Johan Hevelius (1611-1687). Hevelius, a wealthy brewer (I like him already) and city councilor, decided to build an observatory in the town of Dantzig (modern day Gdansk). He built “Sternenburg” Observatory, on the top Sextans, a small constellation wedged in Planetary nebula are few in Sextans with floors of four houses. There he installed between Leo, Hydra and Crater, is IC314 our only target. IC314 is very a radically new, 140' focal length another constellation with no remarkable faint (14.3 mag.) and slightly irregular in refractor with an open tube, called an bright stars. The brightest star, Alpha shape, with an elongation to the east. “air telescope.” Using this telescope, Sextantis, is only 4.5 magnitude, and lies Seeing the faint glow will take at least Hevelius made many contributions to 12 degrees due South from the much 12", due to its low surface brightness. astronomy, including: brighter Regulus. This small constella- tion will require some skill and large For galaxies, Sextans doesn’t disappoint. The determination of the solar telescopes to view some of its hidden Although it doesn’t host any famous rotation period with considerable treasures. bright objects, like its neighbor Leo, it accuracy from sunspot observations does contain a few worth a look. The in 1642-1645. For the double star observer, there are brightest galaxy, NGC 3115, also called two of note in Sextans. The first, “The Spindle Galaxy” is the best of the Detailed maps of the Moon which he Gamma Sextantis, is a multiple binary group. This edge on spiral at 21 million published in his “Selenographia.” system. The primary pair, at 5.6 and 6.1 light years distant is 4’X1' in size. It has magnitudes, have a separation of .6 arc a nice taper from end to end, appearing The publishing of his many years of seconds, a challenge for most scopes. as a spindle, but has no distinct dust lane comet observations in “Prodomus The third star in the system, a faint 12th like other edge on spirals. Because of Cometicus” in 1665, followed by magnitude yellow star lies 36" away at this, it is considered to be a S0 type “Cometographia” in 1668. PA of 325°. The other double is 35 galaxy, an intermediate form between Sextantis, a nice orange and yellow pair elliptical and spiral. Sole discovery of Nova 1670 Cygni. of stars with magnitudes of 6.3 and 7.4. With a separation of 6.8" of arc, this A nice trio of galaxies, four degrees to And of course, his star catalog, pair should be easy in most scopes. the NE of Alpha Sextantis, is NGC “Uranographia,” published posthu- 3165, 3166 & NGC 3169. The two mously by his wife, four years after his For globular clusters, Sextans only has larger galaxies, 3166 and 3169, are only death. In this catalog of 1564 stars, is one, and it’s a challenge for even the six million light years from each other. where his new constellations, includ- largest scopes. PAL 3, one of the 3166 and 3169, at 10.5 and 10.3 respect- ing Sextans, first appear. It’s said that famous Palomar Globulars, lies 45 fully, should be visible in scopes of 8" or he created the constellation of minutes to the NW of Alpha Sextantis. more. 3165, at 13.9 magnitude, will take Sextans to commemorate his favorite This globular, with a magnitude of 14.7, 12" or more to detect. observing tool, a sextant that was lost will challenge all who try to grasp its when his home burnt down in 1679. faint light. Astro 101 continued on page 3 Page 2 SAN DIEGO ASTRONOMY ASSOCIATION NEWS AND NOTES, APRIL 2005 San Diego Astronomy Association Similar to NGC 3115, NGC 3044 is Object name: IC 614 Object name: NGC 3166 another edge on spiral that has a very Magnitude: 14.3 Magnitude: 10.5 skinny appearance in the eyepiece. At Equatorial 2000: RA: 10h 26m 52s Dec: Equatorial 2000: RA: 10h 13m 46s Dec: 11.4, it should be visible in an 8" scope, -03°27’53" +03°25’33" but I think it will take 10" to see it Size: 0.8 x 0.8 Size: 4.8 x 2.3 clearly. Surface brightness: 12.9 Surface brightness: 13.0 Dreyer description: Very faint, diameter Dreyer description: Bright, pretty small, I hope you’ve enjoyed this tour of irregular eastward. round, westward abruptly much brighter Helevius’s Sextant. middle, 2nd of 3. Object name: Spindle Galaxy, NGC Object name: Gamma Sextantis 3115 Object name: NGC 3169 Other ID: HIP 48437, SAO 137199 Magnitude: 9.1 Magnitude: 10.3 Magnitude: 5.07 Equatorial 2000: RA: 10h 05m 14s Dec: Equatorial 2000: RA: 10h 14m 15s Dec: Equatorial 2000: RA: 09h 52m 30.413s -07°43’05" +03°28’01" Dec: -08°06’18.356" Size: 7.2 x 2.4 Size: 4.2 x 2.9 Alternate names: HIP 48437 GSC Other ID: Spindle galaxy Surface brightness: 12.9 5475:1379 PPM 192845 Dreyer description : Very bright, large, Dreyer description: Bright, pretty large, Spectral: A2V very moderately extended 46°, very very little extended, pretty gradually gradually abruptly much brighter middle much brighter middle, 11th magnitude Object name: 35 Sextantis extended nucleus. star, 78°, 80", 3rd of 3. Other ID: HIP 52452, SAO 118449 Magnitude: 5.77 Object name: NGC 3165 Object name: NGC 3044 Equatorial 2000: RA: 10h 43m 20.927s Magnitude: 13.9 Magnitude: 11.8 Dec: +04°44’51.438" Equatorial 2000: RA: 10h 13m 31s Dec: Equatorial 2000: RA: 09h 53m 41s Dec: Alternate names: HIP 52452 GSC +03°22’30" +01°34’46" 257:1275 PPM 157110 Size: 1.3 x 0.7 Size: 4.7 x 0.7 Spectral: K3III+... Surface brightness: 13.6 Surface brightness: 12.9 Dreyer description: Very faint, moder- Dreyer description: Very faint, very large, Object name: Pal 3 ately extended 0°, 1st of 3.