Disassembly Pictures for NexStar GT Altitude
Axis
In chapter 12 of the NexStar User's Guide I describe how to disassemble,
reassemble and adjust the NexStar GT mount. I included as many
pictures as was practical for a book, but thought additional pictures would
be useful. Note that the book describes more detail; these pictures
are meant to supplement.
Caution! The very real possibility exists during the procedures
described here that you may damage something. Also, disassembly may void
your warranty and you should consider returning your telescope for warranty
work rather than attempting adjustments on your own. After the warranty has
expired you should consider the possibility that you will cause costly
damage when working on your scope. While I consider the following procedures
reasonably safe, not everyone should approach an expensive piece of
equipment with a screwdriver in their hand.
Click any of the pictures below for a larger version.
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In this view, the tube ring is opened
showing the nut that holds the tube ring to the altitude axis. |
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After removing the nut and tube ring, I
have laid out all the parts in order. Note the red fiber disk.
The surface of this disk, as well as the area of the large gear that
the disk mates to, must be free of grease. |
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When reassembling, first you will replace
the large washer, then the lock washer and finally the large nut. |
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On some models, particularly those with a
plastic tube ring, you may find that the large washer has been
replaced by a large metal plate like the one shown to the left.
This plate distributes the force of the nut across more of the plastic
surface. The top photo clearly shows the plate while the bottom
photo shows the plate in its correct location. Photos courtesy Larry
Stedman and Donna. |
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This view shows the large gear removed
from the fork arm. Note the large white nylon washer
and 3 white nylon disks that provide the bearing surface between the gear and the
fork. The 3 disks must be
replaced in the recesses in the fork arm prior to reassembly. |
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In this view, I have removed the outside
cover of the fork arm - it is held in place by two recessed screws.
With the cover removed, you can see the nut securing the outside end
of the altitude axis. |
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When reassembling the outside end of the
altitude axis,
first you will replace the plastic washer, then the flat washer, then
the cone-shaped washer (large side down) and finally the nut. |
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To correctly adjust the tightness of the nuts, first tighten the
nut inside the tube ring as much as you like. This nut simply allows the
optical tube
to slip up and down at the point of the red disk, should you need to move the
mount by hand (during storage). In practice, we never move the
mount by hand. Next tighten the nut under the outside fork arm
cover just to the point where
the tube ring no longer rocks back and forth. Too tight on the
outside nut and the mount may not move freely, tracking will suffer and
battery life will be shortened. Apply power to the mount and
ensure free movement for 360 degrees. Adjust the outside nut again
if necessary.
See The NexStar User's Guide for
more details on adjustments, cleaning and lubrication of the axis. |
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