NexStar Resource Site

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The NexStar User's Guide II - Excerpt from Chapter 7

NexStar Control Protocol

Communication protocols have various technical parameters to allow two devices to communicate over some medium. Both devices must utilize all the same parameters or communication will not be possible. The NexStar+, NexStar version 4 and StarSense hand controls share the same protocol which traces its roots back to the Celestron Ultima telescopes of the 1990s. It is useful to understand how this protocol evolved since the introduction of the first NexStar telescope in 1999.

  • The first NexStars on the market were the original NexStar 5/8 sold from 1999 to mid-2002. These scopes had a silver optical tube and no connector ports on the top of the mount. They also have a control protocol unique to them, so if a software package does not state specifically that it is compatible with this mount, it most likely will not communicate.
  • Next on the market were the NexStar GTs in 2000. The original hand control can be identified by a lack of the alignment option named Two Star Align. The original hand control had a slight change to the control protocol from the NexStar 5/8 and thus introduced the second unique protocol. There are very few software packages compatible with this hand control.
  • With the advent of the NexStar GPS series in 2001, Celestron introduced what would become their final (up to this time) control protocol. All Celestron computerized mounts introduced since then use this control protocol.

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Michael Swanson
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