With the 12.5" F/5 having a focal length of around 1580mm, you are going to experience star trailing much sooner than you think. 2 to 3 minute exposures are too long for unguided exposures at this focal length.
Refer to these formulas.
http://www.astropix.com/GADC/SAMPLE7/SAMPLE7.HTM
In the example provided a 50mm lens will experience trailing in 8.5 seconds along the celestial equator.
If anything, hit the bright objects, but certain keep exposure times very low.