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Disassembly Pictures for NexStar 5/8/5i/8i Azimuth Axis

In chapter 12 of the NexStar User's Guide I describe how to disassemble, reassemble and adjust the NexStar 5/8/5i/8i 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.

The pictures below were provided by Brian Schilt - thanks Brian! 

Click any of the pictures for a larger version.

Disassembly of the azimuth axis starts by removing the battery cover and then removing the four screws that hold the base cover (with the battery compartment).  You may have problems removing the base cover with the inside fork arm cover in place.  Sometimes it is enough to simply loosen the two screws at the bottom of the inside fork arm cover, other times you might need to remove it entirely.  If you must remove it entirely, you will first need to remove the optical tube as shown here.
After lifting up the base cover, you will find a cable running to the battery compartment.  You may want to disconnect this cable as you work.  The connector is generally "keyed" to fit only one way, but it might be advisable to note the orientation for reassembly.  After the cover is removed, you will find one circuit board on the NexStar 5/8, two circuit boards mounted together on the NexStar 5i/8i.  Like most electronics, these boards are sensitive to static electricity.  Be sure to touch a grounded object (the metal chassis of a PC, refrigerator or washing machine for example) before proceeding.  Remove the screws holding the board(s) to the base and you can move it aside.  If you decide you must disconnect the wires to the circuit board(s), make a sketch to insure you replace them correctly - mistaken connections can definitely damage a circuit board.
After removing the circuit board(s), you will be able to remove the large nut and washer holding the base together.
Once the nut is removed, the top and bottom of the base pull easily apart.  Note the three nylon disks which in this picture adhered to the track in the top half of the base.  When reassembling, place the disks in the recesses in the large gear.

After reassembling all the parts, tighten the large nut just to the point where the fork arm no longer rocks back and forth.  Too tight on the 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 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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Michael Swanson
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