NexStar Resource Site

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PC Port Cable for Celestron Scopes

A cable can be connected from the serial port of a computer to the PC Port on the base of the GPS, CPC and CGE telescopes.  The same cable can be used with the AS-GT, CGEM, NexStar 5i/8i, NexStar SE and NexStar SLT with an optional Auxiliary Port Accessory Kit (part number 93965) from Celestron.  The two uses of this connection would be to run NexRemote without the use of the real hand control and to update the motor control firmware in the mount.  You can order the cable from many Celestron dealers (Celestron part number 93922).

The PC port on the base of the scope is a standard RJ-45, so it is fairly easy to build a cable using a flat RJ-45 cable and a DB-9 (female) to RJ-45 adapter.  The following is the end of the cable that plugs into the PC port on the scope.  Insure that the leads indicated connect to the correct pins on the DB-9 serial port connector shown below.

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NexStar End of PC Port Cable
(connects to PC Port on NexStar base)


DB-9 End of PC Port Cable
(connects to serial port on the computer)


DB-9 to RJ-45 adapters and RJ-45 cables can be purchased at (search for "db9 rj45" for the adapter).  The picture below shows a typical adapter.  Pre-built cables are sold by most Celestron dealers under the name "programming cable".

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Michael Swanson
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