Your ph test is pretty close for your high alk. At normal atmosphere CO2 levels you can always know the ph unless you've really screwed things up by dosing too many chemicals. I can't rememeber the last time I checked ph on my tank. I just keep an eye on the alk and keep my house aired out so I don't build up CO2 levels in the room, which will drive down the ph. That's a real common problem this time of year with the mild weather because ac/heat is not running as much. Lot's of stuffy houses LOL.

There's a chart to tell you the ph for a given alk here...
http://www.reefkeeping.com/issues/2005-03/rhf/index.php