jrasc june 1998 final - The Royal Astronomical Society of Canada

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jrasc june 1998 final - The Royal Astronomical Society of Canada

The great 4th magnitude globular cluster Omega Centauri was obviousto the naked-eye, peaking as high above the southern horizon as Spicadoes in southern British Columbia. (Photo by Dave Lane, Ram Krishnan,and Greg Palman using a 130-mm Astro-Physics refractor and a CCDCamera designed and constructed by Ram)display from the darkened decks of the M.S. Veendam duringFebruary’s New Moon. After midnight the huge Eta CarinaeNebula, the brightest patch in the southern Milky Way, culminated18 degrees above the Caribbean Sea. The nebula is flanked bytwo very prominent naked-eye open clusters, oblate NGC 3532three degrees to the ENE and the bright stars of IC 2602, theTheta Carinae cluster, five degrees to the south.Virginian Kent Blackwell had brought tripod-mounted1930s-era 20120 Japanese battleship binoculars. They revealedthe chevron-shaped dark lane in the great emission nebula andunveiled the third large galactic cluster near Eta Carinae,unresolved NGC 3114. Kent spotted Comet Hale-Bopp with thegiant binoculars. (I said I would look in a few minutes and thenfrankly forgot — I was too entranced with the Eta Carina area.)On the night of February 27/28 we sailed east from Bonaireto Grenada along latitude 12 degrees, the southernmost leg ofthe voyage. Achernar was visible just before it set during eveningtwilight — it had eluded me longer than any other 1 st magnitudestar in the entire sky.That night I used my 4-inch Astroscan and my 750binoculars from midnight until dawn. At 64 the Astroscanrevealed the many long star-chains forming NGC 3532’s overallfootball shape. One orange star highlights the cluster. In additionto the three large galactic clusters escorting the Eta CarinaeNebula, the Astroscan found other smaller clusters nearby. Thetwo best were adjacent NGC 3293, enmeshed in faint nebulosity,and bright compressed NGC 3766 in Centaurus, between EtaCarinae and the Southern Cross. The Coal Sack dark nebulawas obvious to the unaided eye. My 750 binoculars showedseveral parallel dark bands in the dust cloud, the northern onebeing the most opaque.The famous Jewel Box cluster was a disappointmentthrough both the 4-inch Astroscan and the giant binoculars— perhaps a larger telescope is required to allow it to live upto its reputation. The Astroscan showed only 12 stars at 64,none of them with any noticeable colour.The great 4 th magnitude globular cluster Omega Centauriwas obvious to the naked-eye, peaking as high above the southernhorizon as Spica does in southern British Columbia. My smallreflector resolved the elliptical globular’s 11 th magnitude starsat 64. Alpha Centauri’s two yellow components were separatedby 21 arcseconds, almost the widest that they ever become intheir 80-year orbit.The 750s swept up numerous unresolved open clustersfrom Triangulum Australe through Norma and up into the tailof Scorpius. After all of these fuzzies, the bright gems of M7were a treat. (M7 was halfway to the zenith on that memorablemorning.)One of my long-time naked-eye favourites is the cometlikestructure headed by the wide double star Zeta Scorpii. Thewonderful open cluster NGC 6231 forms the “coma” while theadjacent large cluster H12 makes “the comet’s tail.” Has anyoneelse noticed this illusion?The closest globular cluster is NGC 6397 in Ara, at a distanceof 9000 light years. I located it easily with the Astroscan’s threedegreefield of view at 16, but I had a devil of a time viewingit at 64 — it took me a frustrating half-hour. I would centreit at 16, change eyepieces, refocus, and it would then be gonebecause of the rolling of the ship which had increased as morningapproached. Only a scattering of 10 th magnitude stars was“While I had no difficulty navigating thefar southern sky, familiar northernconstellations held surprises.”resolved at 64 by the little reflector as the very rapid tropicaltwilight rolled up the sky.While I had no difficulty navigating the far southern sky,familiar northern constellations held surprises. Corvus waswell above Spica when rising, which never happens at home.Boötes passed north of the zenith, hanging head down fromArcturus. Conversely, by following the same course, kneelingHercules was made into an upright figure with his head towardsthe zenith. No circumpolar stars were visible between low-lyingPolaris and the sea.The evening sky was viewed last, on the 28 th , as we sailedfrom Grenada, heading north from our southernmost port atlatitude 12° 03´ N. At the end of astronomical twilight my 750binoculars easily found the Large Magellanic Cloud (LMC), onebinocular field above the sea horizon. Only the 3-to-4 degreecentral bar was visible, but it was unmistakable from havingJune/juin 1998 JRASC159

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