[PSUBS-MAILIST] measuring an angle issue

[hank pronk via Personal_Submersibles]

Hi All,  I am planing to remove my original conical port and instal a dome on the original conical seat and bore the centre out of the original seat to get 12 inches of open view.  Will Cohen is making the dome for me.  My problem is, I have to measure the seat angle to within 1\4 of 1 degree.  How can I measure this angle without buying an expensive digital protractor?  I thought about just measuring the distances of the angles and just do the math, but it is pretty tricky to measure.Hank
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