Gear for Photographing naked-eye comets

Folks--Thanks for the feedback.  I should have guessed practice, practice, practice.

I completely agree that it's anybody's guess about how PanSTARRS and ISON might present themselves.  So I looked for objects of different magnitude and found these two that could keep me busy:

• The moon in different phases (detail, brightness variation)
• The International Space Station (a smaller, bright object)

Any other suggestions for practice subjects?

If anything is overhead, maybe I'm going to need to jerry-rig a viewfinder, and/or use live-view... or shell out for a VF adapter.  I'll see what happens, but also will accept any feedback that anyone has on that.

A good test-drive is just the prescription.  I'll try to post some results.