Appendix c - rs-232 connection – Celestron NexStar 80GTL User Manual
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Appendix C - RS-232 Connection
You can control your NexStar telescope with a computer via the PC port on the hand control and using an optional RS-
232 cable (see Optional Accessories section of manual). Once connected, the NexStar can be controlled using popular
astronomy software programs.
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P
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:
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The NexStar telescopes communicate at 9600 bits/sec, No parity and a stop bit. All angles are communicated with 16
bit angle and communicated using ASCII hexadecimal.
Description
PC Command
ASCII
Hand
Control
Response
Notes
Echo
Kx
X#
Useful to check communication
Goto Azm/Alt
B12AB, 4000
#
10 characters sent. B=Command,
12AB=Azm, comma, 4000=Alt.
If command conflicts with slew
limits, there will be no action.
Goto Ra/Dec
R34AB,
12CE
#
Scope must be aligned. If
command conflicts with slew
limits, there will be no action.
Get Azm/Alt
Z
12AB,
4000#
10 characters returned,
12AB=Azm, comma, 4000=Alt, #
Get RA/Dec
E
34AB,
12CE#
Scope must be aligned
Set Azm-Alt
S12AB, 4000
#
10 characters sent. S=Command,
12AB=Azm, comma, 4000=Alt
Cancel Goto
M
#
Is Goto in Progress
L
0# or 1#
0=No, 1=Yes; "0" is ASCII
character zero
Is Alignment Complete
J
0# or 1#
0=No, 1=Yes
The cable required to interface to the telescope has an RS-232 male plug at one end and a 4-4 telephone jack at the
other end. The wiring is as follows: