Readying your polar alignment scope's 'slide rule'.
With the polar alignment scope aligned with the RA axis you're now ready to set the 'zero points' of the circular slide rule (a combination of the date/time circle and the RA setting circle) so that you can use the polar scope to properly put the X on the north celestial pole.

The first thing you're going to do is to setup the polar scope so that it is set for when Polaris is in transit. To do this rotate the RA axis while looking into polar scope and placing the Polaris circle directly BELOW the X. This is a standard refractor remember and therefore is inverted. Hint.. to get the reticle set vertical point the polar scope at a door frame from across the room and line it up with the edge. That should get you within a degree or so of vertical.



There are two different reticules... but the theory is the same for both.

Zeroing the 'slide rule'
  • Turn the RA axis so that the reticule is as above with the small circle 'down'
  • Clamp the RA axis.
  • Place the 0h mark on the RA setting circle under pointer.
  • Rotate the RA axis so that 01h 26m is under the pointer. (This is STANDARD time NOT daylight savings time)
  • Lock the RA axis.
  • Rotate the date/time circle so that the RA pointer is pointing at October 10.
  • Un-clamp the RA axis and turn the scope to place the 0h mark under the RA pointer.
  • Look through the polar scope... you should be back to where the Polaris circle is directly under the X.
  • Clamp the RA axis.
  • Loosen the set screw in the ring next to the date/time circle and rotate the circle so that the pointer (a narrow slot... fill it with white crayon or something) is pointing at 0 on the longitude scale on the date/time circle.
  • Tighten the set screw.
  • Now your 'slide rule' is set.


Fine tuning

If you wish to fine-tune for your observing site this is easy. First calculate how many degrees east or west of the standard meridian your observing site is. For my site the longitude is -81 and the standard meridian is -75. So, I'm 6 degrees west of the standard meridian. Now, move the date/time ring looking at the 'longitude' scale so that the correct offset is over the date/time index mark. For me this would be 6 degrees west. You can adjust this for any observing site that you will be going to and return it as needed. As long as you don't unlock the date/time index ring you can adjust at will.

Now you're ready to use the polar alignment scope to get your RA axis pointing in the right direction. On to

Polar alignment.