Using the Tracking Mount

Before using the mount, it is important that its drive rate be set so that the large gear (with its attached nut) rotates once per minute. This can be easily accomplished by putting a small permanent mark on one tooth of the large gear as well as a small index mark on the bottom plate next to the gear. One simply adjusts the supply voltage until it takes a minute for the gear to make one revolution. Additional accuracy can be achieved by timing for a longer period, say 5 minutes. Be aware that the power supply output voltage (and tracking rate) can vary as battery voltage drops as well as with temperature changes. So it might be best to check the drive rate before each photo session.

Also note that after about a cumulative hour of tracking, it is necessary to reset the mount  as follows:

  • Lift the upper plate, disengaging the gears.
  • Spin the large gear and its nut until it snugs up against the upper plate.
  • Lower the plate and re-engage the gears. This will enable another hour or so for tracking. 

If care has been taken in constructing the mount according to the dimensions in Gary Seronik's plan, with careful polar alignment, and careful adjustment of the motor speed, this mount can easily provide tracking for some nice astrophotos. I have found that ISO 800 or 1600 with a 2 minute exposure gives nice results. Some of these results are on the next page.