Installing the G11/GM-8 Polar Finder


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For reference, the pieces of the polar finder are shown below (Figure 1).

Figure 1. Polar finder parts.

  • Some polar finders come with a metal washer instead of the plastic washer. The purpose is to allow the finder to be rotated, yet held in alignment. The retaining ring should be tightened just enough to allow rotation of the finder. The setscrew in the retainer ring is meant to hold the retainer at a fixed position but does not have to be used.

  • The objective tube screws into the back end (reticle/eyepiece assembly). Focusing depends on how far in it is screwed. The focus set ring fixes the focus point once it has been determined.

Installation of the polar finder is the same for both the G11 and GM-8 mounts. Unscrew the cap at the end of the RA clutch knob (don't unscrew the clutch knob itself), and the polar finder slides right in. The polar scope's retaining ring screws on using the same threads that the clutch cap used. If you intend to leave the polar scope permanently installed, you no longer need the clutch cap.

In G11 mounts, the polar finder's focus lock ring may sit against the RA axis shaft and prevent the polar finder from being fully inserted into the RA clutch when the clutch is fully tightened. In this case, the focus lock ring outer diameter may need to be reduced so it can go into the RA shaft, or washers may be added ahead of the RA clutch to move the clutch further out. Normally, these thick spacer washers are provided with the G11, but may have gotten lost if digital setting circles were installed, then removed from the mount. This should not be a problem on mounts with digital setting circles as the installation of the RA encoder adds sufficient distance between the clutch and RA shaft to fully insert the polar finder.

Figure 2. RA clutch with cover removed, ready for installation of the polar scope.

Since The polar finder screws into the bottom of the Losmandy mount RA clutch the polar finder will rotate when the clutch is turned (it is not a defect), but this does not affect use of the polar finder since the clutch is not normally turned during the polar alignment procedure.

To sight Polaris, remove the polar scope cover opposite the RA clutch knob end of the RA axis. Looking down the polar axis, rotate the Dec axis until the hole in the axis is oriented so that the polar scope is visible. Depending on your mount's saddle arrangement, this should be at either 0 degrees Dec or +/-90 degrees.

Copyright 2001 by David A. Kodama, All Rights Reserved