Finding M81-M82 in the Coma Sculptor Group
M81 and M82 northwest of UMa's big dipper asterim are showcase objects for which one can practice star hoping via bright locator stars using binos from a urban light polluted observing point. Showcase galaxy overview chart of UMa - Spring Orientation 41 deg north latitude http://www.slas.us/gallery2/main.php?g2_itemId=3256 I like to star hop to M81-M82 from a west entry at omicron UMa (Muscida): M81-M82 finder chart in spring orientation for 41 deg north latitude http://www.slas.us/gallery2/main.php?g2_itemId=3259 Using 5 deg binos under a light polluted mag 4.0 sky, from omi UMa the wing-v asterism anchored by pi2 UMa (SAO14616). Once the wing asterism is found, slewing to the west reveals a prominent triangle asterism anchored by rho UMa (SAO14742). Finally, single star 24 UMa (v4.6) is found. From 24 UMa, a right ascension slew of about 1 degree using a 1 degree TFOV telescope eyepiece should run across the M81-M82 galaxy pair. Showcase galaxies of Ursa Major provide an instructive lesson on 2D projections of objects on the celestial sphere verseus their actual 3D structure. M82, M82, M101, M108 and M109 all are physically within the constellation of UMa, they are members of different galaxy groups at different differences. M81 and M82 (and M51 and M101) - although in UMa - are part of the closer Coma Sculptor Galaxy Group and not the UMa Group - 3D Chart of the Coma Sculptor Galaxy Group Z-Y galactic plane view http://www.slas.us/gallery2/main.php?g2_itemId=3244 Color coding - Dark Blue Local Group Red Coma - Sculptor Cloud Green - dark Leo Cloud Green - light Leo Spur Purple Triangulum Spur Teal Virgo Cluster and Southern Extension Yellow - dark Fornax Cluster and Eridanus Cloud Yellow - light Dorado Cloud Black Not coded in this view In contrast, UMa 108 and M109 are part of the much more distant Ursa Major Galaxy Group: 3D Plot of Ursa Major Group http://www.slas.us/gallery2/main.php?g2_itemId=3262 Color coding - Red Ursa Major Cloud Red - light Ursa Major Southern Spur Green - dark Canes Venatici - Camelopardalis Cloud Green - light Canes Venatici Spur Purple Cetus - Aries Cloud Teal Virgo-Libra Cloud Yellow - dark Pegasus Cloud Yellow - light Pegasus Spur and Perseus Cloud Black Not coded in this view The star hop from omicron UMa is good after work practice with binos to prepare for finding M81-M82 with a telescope during a dark sky weekend. Clear Skies - Kurt
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