I decided to make an altitude scale for my 8" dob. After much experimentation I devised a method using a lightscribe CD. In Photoshop I made a 12cm circle then drew a 0 to 90deg scale around 1 quarter of it. I then burnt the image onto a lightscribe CD. Next I removed the thumb screw on the axle of the scope and fitted the CD between the washer & the hud. I used white out to put a mark on the mount near the spring. Using a spirit level I put the barrel on an even plane the losened the thumb screw slightly so I could turn the CD independant of the barrel. I set the 0 deg on the white mark then tightened the thumb screw. That's it, now the Cd turns with the barrel and the white dot indicates the altitude. Cheap and simple. Possibly not accurate to the fraction of a degree but good enough to let you know where your looking.
The only problem I have is the lightscribe is a bit faded looking, I have a friend who can burn white labels so he's doing one for me in clear black on white.
Some photos here plus the original .png file of the scale if anyone else wants to do the same thing.
http://members.optushome.com.au/clarry/1.JPG
http://members.optushome.com.au/clarry/2.JPG
http://members.optushome.com.au/clarry/3.JPG
http://members.optushome.com.au/clarry/4.JPG
http://members.optushome.com.au/clarry/5.JPG
http://members.optushome.com.au/clarry/6.png