Using the STV to Obtain Accurate Polar Alignment

Set up your telescope and STV and roughly align on Polaris. Simply getting Polaris in the finder is sufficient for this step.

For the following steps, the camera head was connected to the scope so that the wire lead is facing down. RA changes will be vertical (y axis on the monitor), and Declination changes will be horizontal (x).

With the OTA on the west side of the mount, point the telescope towards the zenith (directly overhead). Select "Drive Monitor Slow" using the selector on the STV. The output will look something like figure one. The top graph (x axis) will show a line either drifting up or down. Ignore the bottom graph for now.

1) If the line on the top graph is drifting up, move the scope west

a) Move the mount CCW by

b) Turning AZ screws CW (viewed from W site of mount)

2) If the line on the top graph is drifting down, move it east.

a) Move the mount CW by

b) Turning AZ screws CCW (viewed from W side of mount).

3) Repeat this step until there is little or no drift on the top graph.

Point the scope to a star in the east that is at about the altitude of Polaris.

1) If the line on the top graph drifts up, increase the altitude angle of the mount (rotate alt knob clockwise)

2) If it drifts down, decrease the altitude angle of the scope (rotate alt knob CCW).

Repeat this step until the top line shows little or no drift.

Repeat steps two and three until there is no drift in the top graph for at least one complete cycle. At this point, the bottom graph will represent your drive's periodic error and your scope is perfectly polar aligned.

After three or four tries, I was able to repeatedly align my scope within 10 to 20 minutes, depending on the accuracy my initial setup.

Dick Locke, 12/17/02

Losmandy GM-11 instructions adapted from http://www.melino.org/astronomy/polar_align.html