Appendix C - Rs 232 Connection; Communication Protocol - Celestron NexStar 114 Instruction Manual

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.
C o m m u n i c a t i o n P r o t o c o l :
C o m m u n i c a t i o n P r o t o c o l :
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
Echo
Goto Azm/Alt
Goto Ra/Dec
Get Azm/Alt
Get RA/Dec
Set Azm-Alt
Cancel Goto
Is Goto in Progress
Is Alignment Complete
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:
PC Command Hand
ASCII Control
Response
Kx X#
B12AB, 4000 #
R34AB, #
12CE
Z 12AB,
4000#
E 34AB,
12CE#
S12AB, 4000 #
M #
L 0# or 1#
J 0# or 1#
39
Notes
Useful to check communication
10 characters sent. B=Command,
12AB=Azm, comma, 4000=Alt.
If command conflicts with slew
limits, there will be no action.
Scope must be aligned. If
command conflicts with slew
limits, there will be no action.
10 characters returned,
12AB=Azm, comma, 4000=Alt, #
Scope must be aligned
10 characters sent. S=Command,
12AB=Azm, comma, 4000=Alt
0=No, 1=Yes; "0" is ASCII
character zero
0=No, 1=Yes