PC Control of
NexStar Telescopes
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General Info
It is first important to understand that there are currently seven different NexStar
hand controls on the market. In order of their introduction:
- NexStar 5/8
- Original NexStar GT (60/80/114/4)
- NexStar GPS
- New NexStar GT (introduced in December 2001)
- Hand control version 2.2 and 2.3 for the the NexStar 5i/8i/8i
Special Edition and NexStar GPS
- CGE Series
- AS-GT Series
- Hand control version 4 - introduced with the CPC and compatible
with the NexStar GPS, CPC, SE, SLT, GT, "i" series, CGE,
AS-GT and StarSeeker
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All of these scopes are connected to a PC or PDA via the
RS-232 port on the bottom of the hand control. (For more
information about the various ports and connectors on your scope,
visit the Odds and Ends section of the web site.) The correct
cable is described in the link "Hand Control (HC) RS-232 Port Cable" above. The link
provides the information you need if you want to build a cable
yourself and it provides a source for purchasing pre-built cables. If your
PC does not have a serial port (very common with today's
laptop/notebook computers) you will also need a USB to serial adapter
- these are available at most computer stores for about $30.
PDAs (Palm Pilot, Pocket PC) require a serial "sync" cable or a serial port CF card in addition to the
HC RS-232 Port Cable.
Additional details for all of this are found in my
book. Also, be sure to check out Larry McNish's diagram
linked above. Hand Control
Version 4
Hand control version 4 is compatible with the CPC, NexStar GPS,
NexStar 5i/8i/8i Special Edition, NexStar SE, NexStar SLT, NexStar GT,
StarSeeker, CGE
and AS-GT scopes. The command set for this and most other versions of
NexStar hand controls can be found in the link "Programming for NexStar
Controlled Telescopes - Documentation and Examples" above. Any program compatible with the NexStar GPS is
basically compatible with this hand control, regardless which telescope you use it
with, so if the setting for your particular scope doesn't work correctly,
try NexStar GPS.
NexStar GPS
The NexStar 8/9.25/11 GPS control commands are detailed in a document
from Celestron found in the link "Programming for NexStar Controlled
Telescopes - Documentation and Examples" above. The control
commands are quite similar to commands for the Celestron Ultima 2000
(U2K). Some telescope control programs that work with the U2K will work with the
GPS, try that selection if a setting for the NexStar GPS is not available.
NexStar GT
The newer (version 101.0 - see Firmware Versions on this web site) NexStar GT hand control is capable of interfacing with PC based
programs as documented in the latest NexStar GT manuals.
However, the NexStar 4 manual does not document this. If you own a
NexStar 4, you might want to download the new 60/80/114/130 manual from the
Manual section of this web site.
The GT control commands are detailed in a document from Celestron found in
the link "Programming for NexStar Controlled Telescopes - Documentation and
Examples" above - it is the same basic command set as the NexStar GPS.
If a programs doesn't have a setting for NexStar GT or if it doesn't work,
try the NexStar GPS setting.
NexStar 5i/8i/8i Special Edition
The computerized hand controls for the NexStar 5i/8i/8i Special Edition
(sometimes called the "iComp" hand control) are direct descendants of the GPS hand control and share the
same command set as detailed in a document from Celestron found in the link
"Programming for NexStar Controlled Telescopes - Documentation and Examples"
above. If a programs doesn't have a setting for NexStar 5i/8i use the
NexStar GPS setting.
CGE and Advanced Series with GoTo
The CGE and AS-GT control commands are detailed in a document from
Celestron found in the link "Programming for NexStar Controlled Telescopes -
Documentation and Examples" above. If a programs doesn't have a
setting for CGE or Advanced Series, use the NexStar GPS setting.
NexStar 5/8
The control commands
for the original NexStar 5/8 (not the 5i/8i) are documented in their manual. It should noted that some, if not all, of the N5/8 hand controls
exhibit a problem where occasionally they do not reply back to the PC after
they finish slewing. If a PC control program does not take this into
account, it might wait forever for the slew to finish.
Original NexStar GT
The original NexStar GT hand control (the hand control for NexStar 60/80/114/4
scopes made prior to January 2002 and all Tasco StarGuide scopes) is capable of interfacing with PC based programs; all
required commands are documented in the "Original GT Model Control Commands"
link found above. But there are some problems (explained in the link
above) that make it less than enticing for commercial developers and so most
software does not support the original GT hand control. If you have a
NexStar scope, contact Celestron (www.celestron.com)
to inquire about an upgrade to the version 4 hand control.
Most of the information you find here is the result of my work on NexStar
Observer List, a PC control program for all models of NexStar scopes.
You can learn more and download your free copy here.
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