What kind of lamp to use with a stroboscopic disc?

Thanks for telling us about the app, brf.  I would never have thought to check for an app.  If you are too non-tech to go that route, the no-brainer solution is to buy the hand-held, battery powered strobe from KAB.  Along with their strobe disc, you will have a very accurate estimate of speed.  The others are correct to say that depending upon a steady 60Hz AC line frequency powering the bulb is chancy.

The KAB battery strobe is the way to go, but the strobe disc you 'printed out' is only partially accurate.  You really need to purchase the "Cardas Frequency Sweep and Burn-In Record.  It has a set of various strobe speeds printed on the label.  You should set your table speed with the stylus engaged into a record grove.  Believe it or not the slight, minuscule drag from the diamond in the groove will create RPM loss, which may lead to unhappy listening sessions. Some people  even run a bit of 'advance' on their tables, which is more pleasing to the brain for some odd reason.

quincy, "a bit of 'advance' on their tables, which is more pleasing to the brain for some odd reason"

I expect that "lively" sounds inherantly better than "draggy". ;^)