145 CMa - the Winter Albireo - a colorful after-work winter double Feb-Mar 

Finder: http://members.csolutions.net/fisherka/astronote/finder/CMa_145StarHops.jpg

145 CMa (HD056577) - the Winter Albireo or Herschel 3945 - is at it's most favorable low declination position (J071636.00-231912.0) for 41N op's.  145 CMa is visible in small refractors after sunset from urban light polluted skies.  The Belmont Society Colorful Double Star List describes pi Gem as "orange/blue-green" while Mullaney's _Celestial Harvest_ gives this double an effusive recommendaton.  The primary of this colorful multiple is a v4.8 K4III star at an estimated distance of 536 parsecs. The discover designation - HJ 3945 - attributes first recorded sighting to William Herschel.  At 536 parsecs and G236.50-05.22, this double sits west of Canis Major "down-wind" in the Orion Arm from Sol, in a area rich in small open clusters. 

Current (Epoch 2000) CCDM data on 145 CMa (CCDM 07166-2319) is: 


C PA  sep  mag 
A          4.8 
B 055 26.6 6.8 


145 CMa is about 3 degs east of omi2 CMa.  A courtesy star hopping finder chart is provided at: 

http://members.csolutions.net/fisherka/astronote/finder/CMa_145StarHops.jpg


145 CMa current is low on the horizon from 41N ops - at about only 20 degrees in altitude at sunset. 145 CMa can be star-hopped or right-angle swept by starting at omi2 CMa.  From my light polluted v3.0 urban skies, I began at del CMa and swept north about 3 degs to omi2 CMa. omi2 CMa was just barely naked-eye visible in the light pollution.  Due to light pollution, there were really not any good landmarks to star hop to 145 CMa.  Finding this double is a bit challenging in light polluted skies. Since 145 CMa is a direct east declination sweep from omi2 CMa, I simply used the lowest feasible magnification, with the largest TFOV, about 1 deg in this case - and then counted about 3 1/2 ep views east of omi2 CMa until I saw a small double that looked like 145's namesake - Albireo. 

In a small alt-az 60mm refractor under urban Bortle class 8 mag 3.0 light-polluted urban skies at 22x, 145 CMa lives up to its namesake as the Winter Albireo.  It is a nice, distinct, intense blue-gold pair about 22" apart.  But unlike it's summer namesake, the Winter Albireo is over 500 parsecs distant, while the "real" Albireo is about 125 parsecs away.  On increasing magnification to about 78x, the Winter Albireo the colors fade and somewhat dim in a small refractor. In contrast, the bet Cyg double retains is golden-jewel crispness under higher magnification. 

All-in-all, this was a nice 15-20 minutes of easy after-work viewing at 41N. 

The Belmont Society Colorful Double Star list can be found at: 
http://www.belmontnc.4dw.net/dblstrs.htm 

Prepared 3/2006 K. Fisher fisherka@csolutions.net