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TRUE POLE ALIGNMENT of an
OBSERVATORY CLASS EQUATORIAL

7)

Set HA Verniers into the Meridian by transit of an equatorial star

i) Align telescope on star near culmination.

ii) At time of transit as indicated by the sidereal clock, stop drive.

iii) Adjust HA verniers to 12h & 0h.

iv) Repeat & note HA vernier errors.

Refraction

IMAGE imgs/TRUE_POLE_ALIGNMENT04.jpg

Refraction in dec.

IMAGE imgs/TRUE_POLE_ALIGNMENT05.jpg

Refraction @ HA 6h/18h

IMAGE imgs/TRUE_POLE_ALIGNMENT06.jpg

Depending upon the reading accuracy of your setting circles, the hour axis will now be adjusted close to the true pole, and the meridian error will be much smaller than
the elevation error and of no consequence to the tracking rate. By definition you will possess a filar micrometer or graticule eyepiece to determine arc at the focal plane.
You may now refine the elevation of the hour axis to within ±5"arc of the true pole by observing dec. drift rates due to refraction.