For when the Moon goes away. - Clear Skies, Kurt ------- Fall 2011 Urban Showcase Observing List General situation of the night sky Entering the fall season, the galactic plane lies east-west relative to the local horizon, as opposed to the summer's north south orientation. Galactic longitudes 90 deg (Cygnus) to 175 (M37 to Aur) are well presented. Those galactic longitudes cover the start of the anti-spinward presentation of the galactic disk. In this orientiation of the disk, we look out the at the galactic inside of the next galactic arm away from the galactic core - the Perseus Arm - at an oblique angle. Between the Double Cluster (NGC869-884) and M37 in Auriga, numerous open clusters peak out the inward molecular clouds of the Perseus Arm, including the ET Cluster (NGC457). But in a light polluted urban environment, only a few of the numerous open clusters showcased during this season are not visible. Galactic DSOs are divided by the north and south local horizon hemispheres, with the galactic disk bisecting the sky on an east-west line. The north half of the galactic sphere is on the north half of the horizon; the south half of the galactic sphere is on the south half of the horizon. The north galactic pole in CVn is on or below the northern horizon. The south galactic pole is near Fomalhaut, alf Scl. Like the North Galactic Pole, there is a supergroup of galaxies near the South Galactic Pole. But the South Polar Group is much more distant and fainter. Thus, observable galaxies are much less dense in the south galactic hemisphere, and are limited, in an urban setting, to the Local Group such as M31. Elements of Gould's Belt, a remanent of a 1500 by 1000 ly circular molecular cloud that is marked by bright OB associations. The brightest of these OB associations is the Per OB3 association - a group of bright white stars surrounding Mirfak (alf Per) and del Per. The group is easily seen with wide-field binoculars. The general lack of urban DSO observing opportunities are made up for by a rich field of colorful double stars and two very good planets: Jupiter (in Aries) and Uranus (in Psc). During a light night October session, the following observing list was tested from an observatory in downtown SLC. Several showcase object lists were consulted, and the list is limited to those that tested as urban observable. Fall Urban Showcase List by East-West on local horizon Item Type Const. Dist.ly Comments DSOs NGC6826 PN Cyg 2.4k Blinking Planetary Neb. M15 GC Peg 33.2k Good but ambiguous, Age 13.2b yrs, dia 88lyrs M2 GC Aqu 37.6k Good-ambiguous, Age 13b yrs., 175k stars, dia 175lyrs NGC457 OC Cas 7.9k ET Cluster M52 OC Cas 4.6k Ambiguous but many stars, Age 57myrs NGC225 OC Cas 2.1k Ambiguous but many stars, Age 130myrs M31 Gx And 2.54M Andromeda Galaxy, dia. 3.18 degrees, dia. 141 klyr NGC869 OC Per 6.8k Double Cluster in Perseus Arm Per OB3 OB Per 529 OB Association. Sight on Mirfak, SAO38787, alf Per M45 OC Tau 378 Pleadies with Alcyone system at center, SAO76199, Age 75-150myrs Planets Uranus Psc Meade Star 907, Uranus's north pole is pointed at Earth Jupiter Ari 778M km Meade Star 905, 5.2au, period 11.8yr, mass 318 Earths Colorful Double and Carbon Stars UX Dra C Dra 1.9k SAO9404 gam Del ** Del unkwn SAO106476, equal bright double bet Cep ** Cep 638 SAO10057, True showcase double. Kaler26. del Cep ** Cep 1.5k SAO34508, True showcase double. mu Cep C Cep 2k SAO33693, Herschel Garnet Star, Kaler61. STF 2991 ** Peg unkwn SAO108463, secondary is faint. eps Peg ** Peg 700 Enif, SAO127029, Meade Star 238 91 Aqr ** Aqr 154 SAO146598 94 Aqr ** Aqr unkwn SAO165625, Good. 55 Psc ** Psc 410 SAO74182, Use high power TX Psc C PSC 760 SAO128374 eta Cas ** Cas 18.9 SAO21732 - Colorful 5-star system, VG, plx 168mas iot Cas ** Cas 141 SAO12298, VG sig Cas ** Cas 1.2k SAO35947, Tangey calibration star Polaris ** UMi 426 Meade Star 19, del Cep Type, SAO308, Kaler70. gam And ** And 361 SAO3374-375, True showcase double. 59 And ** And Unkwn SAO55330, Good, no color contrast. gam Ari ** Ari 215 SAO92680-681 alf Ari ** Ari 65 Hamal, SAO75151, VG, Meade Star 17, plx 50mas lam Ari ** Ari 135 SAO75051, VG Teaching moment - Parallax: distance = baseline (a.u.s) x ( 57.3 degs / parallax degs ) Example for eta Cas in Google Calculator 1 a.u. * ( 57.3 degrees / 168 milliarcseconds) in light years Enter: 1*(57.3/((167/1000)*(1/3600))= Returns: 1235209.58 Enter: 1235209.58 astronomical units in light years Returns: 19.5 light years Teaching moment - True diameter from angular diameter and known distance diameter (physical) = distance x ( angular diameter degrees / 57.3 degrees ) Example for M31 2.54Mlyr, angular dia. 3.18 degrees Enter: 2540000.0 x ( 3.18 / 57.3) = Returns: 140963.351 light years. The Milky Way has a diameter of about 100,000 light years.