I use an AKG C414 gold leaf condenser mic.  This is a very good general purpose mic, but I do know that serious studio engineers prefer ribbon or old tube mics for trumpets.  They also prefer very old RCA mics (if memory serves me correctly) as opposed to contemporary ones.  I have played sessions one which the used Neumann (sp?) mics (I think they were ribbon mics).  My knowledge here is a little spotty as I can't afford to buy these right now.  You might look into some high end AudioTechnicas or EV's.  Some folks still use the good old Shure Bros. SM58's.

Have fun! You are wise to record and study your progress in this fashion.

Nick Drozdoff
http://www.geocities.com/Vienna/Strasse/3698