[. . . ] Note: the GT hand control prior to version 104. 0 should be treated as version 1. 2 in the tables below. Version 104. 0 should be treated as version 4. 03. Get Position Commands The following commands retrieve the position of the telescope in either RA/DEC or AZM-ALT coordinates. The position is returned as a hexadecimal value that represents the fraction of a revolution around the axis. [. . . ] This causes future GOTO or Get Position commands to use coordinates relative to the Sync'd position, improving pointing accuracy to nearby objects. (we probably don't need to mention "from the planetarium package" since it also improves pointing accuracy if they GoTo objects via the hand control. ) The format for the RA/DEC positions in the Sync command is identical to the GOTO RA/Dec command. Command Function PC Command Hand Control Response "#" "#" Applies to Versions 4. 10+ 4. 10+ Sync RA/DEC Sync precise RA/DEC "S34AB, 12CE" "s34AB0500, 12CE0500" Tracking Commands The following commands retrieve or set the tracking mode. Depending on the mount type, following tracking modes are available: 0 = Off 1 = Alt/Az 2 = EQ North 3 = EQ South Note: On the CGE and Advanced GT hand control versions 3. 01 through 3. 04 the value for EQ North is 1 and EQ South is 2. This has been corrected to match the other models in current hand control versions. Command Function Get Tracking Mode Set Tracking Mode PC Command "t" "T" & chr(mode) Hand Control Response chr(mode) & "#" "#" Applies to Versions 2. 3+ 1. 6+ Slewing Commands The following commands allow you to slew (move) the telescope at fixed or variable rates. For variable rates, multiply the desired rate by 4 and then separate it into a high and low byte. For example if the desired tracking rate is 150 arcseconds/second, then: trackRateHigh = (150 * 4) \ 256 = 2, and trackRateLow = (150 * 4) mod 256 = 88 For fixed rates, simply use a value from 1-9 (or 0 to stop) to mimic the equivalent hand control rates. Note: in most configurations, issuing the slew commands will override (or conflict with) the tracking mode of the mount. Hence it is always best to disable tracking first using the Tracking Commands, issue the slew command, then re-enable tracking. The main exception to this is when tracking equatorially - the fixed rate slews at 1 or 2 will not override tracking. Note: on GT models, the fixed rate slews at rate 9 move at 3 degrees per second instead of the maximum rate. Command Function Variable rate Azm (or RA) slew in positive direction PC Command "P" & chr(3) & chr(16) & chr(6) & chr(trackRateHigh) & chr(trackRateLow) & chr(0) & chr(0) "P" & chr(3) & chr(16) & chr(7) & chr(trackRateHigh) & chr(trackRateLow) & chr(0) & chr(0) "P" & chr(3) & chr(17) & chr(6) & chr(trackRateHigh) & chr(trackRateLow) & chr(0) & chr(0) "P" & chr(3) & chr(17) & chr(7) & chr(trackRateHigh) & chr(trackRateLow) & chr(0) & chr(0) "P" & chr(2) & chr(16) & chr(36) & chr(rate) & chr(0) & chr(0) & chr(0) "P" & chr(2) & chr(16) & chr(37) & chr(rate) & chr(0) & chr(0) & chr(0) "P" & Hand Control Response "#" Applies to Versions 1. 6+ Variable rate Azm (or RA) slew in negative direction "#" 1. 6+ Variable rate Alt (or Dec) slew in positive direction "#" 1. 6+ Variable rate Alt (or Dec) slew in negative direction "#" 1. 6+ Fixed rate Azm (or RA) slew in positive direction "#" 1. 6+ Fixed rate Azm (or RA) slew in negative direction "#" 1. 6+ Fixed rate Alt (or DEC) "#" 1. 6+ slew in positive direction Fixed rate ALT (or DEC) slew in negative direction chr(2) & chr(17) & chr(36) & chr(rate) & chr(0) & chr(0) & chr(0) "P" & chr(2) & chr(17) & chr(37) & chr(rate) & chr(0) & chr(0) & chr(0) "#" 1. 6+ Time/Location Commands (Hand Control) The following commands set the time and location in the hand control. The format of the location commands is: ABCDEFGH, where: A is the number of degrees of latitude. For example, to set the location to 118°20'17" W, 33°50'41" N, you would send (note that latitude is before longitude): "W" & chr(33) & chr(50) & chr(41) & chr(0) & chr(118) & chr(20) & chr(17) & chr(1) The format of the time commands is: QRSTUVWX, where: Q is the hour (24 hour clock). For example, to set the time to 3:26:00PM on April 6, 2005 in the Eastern time zone (-5 UTC: 256-5 = 251) you would send: "H" & chr(15) & chr(26) & chr(0) & chr(4) & chr(6) & chr(5) & chr(251) & chr(1) Note: All values are sent in binary format, not ASCII. Note: The Get commands do not retrieve the time and location from the GPS unit (if one is present). [. . . ] If serial commands are "blindly" sent without waiting for a response, then some commands may be dropped or the software driver could see responses that are for earlier commands. Pass-through Commands with No Response Commands that start with `P' are special pass-through commands that communicate with a specific telescope device. If a `P' command is sent but no response is returned (because the device is not there or the command is unknown or there was a communication problem) then one extra data byte is returned before the `#' terminating character and any returned data is garbage. This is done to give software drivers a flag that something went wrong so appropriate action can be taken. [. . . ]