hello tempericarus.
I don't think its a good idea to do long shutter speeds (esp 60secs!) with the A+ as there's limited control. but i guess the way to do it is to use a light meter to check the EV, check out the exposure table http://www.fredparker.com/ultexp1.htm , under "Exposure Value Chart"
and find out the shutter speed u need. I think you can time the shutter speed by counting as I doubt very much accuracy is needed (I think tolerance for error can be +- 1sec since its probably under low light condition so your margin of error can be bigger)
LCA+ tends to go wide open under low light (which i assume your in) ie. f2.8 to keep the shutter speed fast. So if your looking at the table, check under f2.8 and iso 100 to know how long to open the shutter under certain EV.
Anyhow, a shot I did by pure guessing using the LCA and a iso 100 film. I left the shutter opened for no more than 5secs though.
