Hi Shaun
To measure altitude I bought a bevel box with a magnetic base.
This sits on my 10" dob. So I can tell what angle it is pointing, it is accurate to within 0.01 of a degree. Basically to start I make sure that my scope is horizontally level and zero the bevel box and bingo any movement measures the altitude. Keep in mind that this only measures "up and down" motion left and right you need setting circle. This link will give you some ideas.
www.ebay.com/bhp/digital-bevel-box