16" Newtonian

Commonly referred to as a Dobsonian or Dob, it's really a serrier truss tube Newtonian reflector on an Alt/Az mount.

2003 Astronomer of the Year

Laying out the tube rings

Square side, round peg

If it's not square at this point, it will through errors into the rest of the calculations.

10" Newtonian reflector

Mounted on an equatorial mount.