M91 appeared circular with a strongly condensed core. A prominent bar crossed the disc at a PA of about 80 degrees. The western half of this bar appeared to be a bit brighter. I couldn’t detect any hint of the extended spiral arm structure.
M91 is a barred spiral galaxy in the Virgo cluster that is receding at about 400 km/sec. Since the cluster as a whole is receding at 1,100 km/sec, the galaxy moving through the cluster at 700 km/sec. It was discovered by Charles Messier in 1781, and is also cataloged as NGC 4548, UGC 7753, MCG+03-32-075, H II-120, h 1345, GC 3093, CGCG 099.096, VCC 1615, IRAS 12328+1446, PGC 41934.
|Subject||M91 (NGC 4548)|
|Classification||Barred Spiral Galaxy (SBb)|
|Position*||Coma Berenices [RA: 12:35:27.2 / Dec: +14:29:48]|
|Size*||5.4′ x 4.3′ – PA: 150° (Bar = 65 °)|
|Brightness*||10.4 vMag; 11.0 bMag; 13.6 Surface Brightness|
|Date/Time||APR 27, 2009 – 12:50 AM (APR 27, 2009 – 07:50 UT)|
|Observing Loc.||Flagstaff, Arizona – Home|
|Instrument||Orion SkyQuest XT8 Dobsonian (203 mm dia./1200 mm F/L)|
|Eyepieces/Mag.||Pentax XW10 (120X)|
|Conditions||Clear, calm, porch lights|
|Transparency||Mag 5.8 NELM|
|*Sources||SEDS; NGC/IC Project; DSS; Starry Night Pro Plus 5; Atlas of the Messier Objects – Ronald Stoyan|