TELESCOPE - COMPUTER CONNECTION

Several configurations of the Intelligent Drive System are possible enabling operation of the telescope at various distances from it. The Drive Box always stays with the telescope and the Intelligent Handset can be up to 20 metres using the standard RJ45 patch cords. This is the first level of remoteness and optionally a computer can be connected at the IH end. No expertise is required to set up this configuration and all the hardware and communication software is present within the IDS.

Remote operation of equipment at the telescope end is accomplished by connecting circuits to the relay interfaces available in the advanced Drive Box product. These circuits could include a DC motor drive for FOCUS ADJUST, switching for a dome rotation motor, filter wheel advance to the next position etc.

To increase the remote operation capability, an extensive command set is incorporated in the IH for operation with a host computer. You will have to write a programme to take advantage of this and it can be done in any language offering access to the computer serial port. There are commands to do nearly everything that can be done through the IH menu system and for pressing certain buttons remotely. Full access is provided to all coordinate and time values to the full resolution shown on the display. In this application the IH can be treated like a black box and there is only a serial port connection to the host computer. The length of this lead can be increased way beyond 20 metres by using RS232 to RS485 converters, or by using modems the sky is the limit!

However most users will have additional equipment at the telescope that needs computer control such as a CCD camera, so in practise the degree of remoteness may be limited, but enough for the observer to stay in the warm.

In deriving the command set for remote operation it was decided to simplify what could be done by making the once off settings to be entered in the IH as normal. So the exclusions are:

• Set latitude and longitude of the observing site.
• Select site number.
• Set date.
• Full calibration of the telescope.
• Full entry of all telescope parameters, drive rates, accelerations etc.

To allow the host programme to work at extended resolution select the AWR protocol in the FACTORY - COMMS screen. There are commands to set the RA and DEC coordinates and to read Right Ascension, Declination, Altitude, Azimuth, Local Sidereal Time, Universal Time and Hour Angle. Once an RA and DEC pair have been sent, a further command can be sent for synchronizing the handset (equivalent to doing a CAL1 calibration) or for slew to the coordinate to operate GOTO's. In addition there are commands to press buttons remotely (U1, U2, U3 and the direction buttons) and perform the action specified. If there is circuitry operated by Relay 1,2,3 then these will then operate remotely. There is also information coming out of the IH to tell the computer when the telescope is guiding which is the trigger to start a CCD exposure for example.

'THE SKY' operates with either IH COMMS mode set to AWR or LX200. The coordinate resolution is automatically adjusted within THE SKY to match that of the handset it is communicating with. Once it is in high resolution mode then 'TPOINT' software can be used to improve the pointing accuracy. It should however be remembered that the virtual encoder resolution is between 10 arc seconds and 45 arc seconds depending on the telescope configuration (gear reductions etc), so TPOINT may not provide full performance. A higher resolution version encoder is being considered for an upgrade.

SKYMAP PRO only works in low resolution mode if "Generic LX200" has been selected. It falls over if the IH has been set to AWR mode. However "Vixen Skysensor 2000" protocol mode works correctly with high resolution data.

STARRY NIGHT PRO also works. ASCOM Interface also works. We have not had any real problems with any planetarium programme providing 'generic LX200' or 'Vixen SS2K' is selected.

Considering full remote control you need to keep an eye on where the telescope is pointing, so monitor the altitude and azimuth ('GA' and 'GZ'). Do this up to twice a second when performing GOTO's so that you can check it is within the allowed envelope of movement for your scope.

Coordinates that are sent from the computer are treated as Jnow (ie epoch of date) and so are NOT precessed.

	/* GETTERS */
	"GR", 		GetRA,
	"GD", 		GetDEC,
	"GA", 		GetALT,
	"GZ", 		GetAZ, 
	"GL", 		GetLocalTime,
	"GC", 		GetCalendarDate,
	"Gt", 		GetLAT,
	"Gg", 		GetLONG,
	"GG", 		GetGmtOffset,
	"GS", 		GetLST,
	"GH", 		GetHA,
        "X?"            GetSLEWstatus

	/* SETTERS */
	"Sr", 		SetObjRA,
	"Sd", 		SetObjDEC,
	"SL", 		SetLocalTime,
	"SC", 		SetCalendarDate,
	"St", 		SetLAT,
	"Sg", 		SetLONG,
	"SG", 		SetGmtOffset,
	"R",  		SetAdjust,         // RG,RC,RM,RS speed set

	/* ACTIONS */

	"Mn", 		MoveNorth,
	"Ms",  		MoveSouth,
	"Me",  		MoveEast,
	"Mw",  		MoveWest,
	"Qn",  		StopNorth,
	"Qs",  		StopSouth,
	"Qe",  		StopEast,
	"Qw",  		StopWest,
	"MS", 		StartGoto,
	"Q", 		StopGoto,
	"CM", 		CalToObj,
	"F",		FnButton,

        /* EVENTS */
        "Xxy",          Tracking status, 0=tracking
        "P",            Periodic error index pulse
        "Sx",           Override active or released
        "Vx",           Backlash state RA
        "Wx",           Backlash state DEC

A few require some explanation:

• To synchronise the coordinate frame with an object (does CAL1) send 'Sr' 'Sd' 'CM'.
• 'Rx' sets adjust speed to Guide or Centre or Move or Slew which is actionned when you command a move 'Mx'.
• 'Fnx' remotely presses USER BUTTONS (n=1,2,3) with x=0 for OFF and x=1 for ON
• 'X?' queries the movement status during GOTO. When it returns to 0 the GOTO has finished. Poll the flag.
• The 'X' event is either 0 or 1 for the two axes independantly. During the GOTO process both axes may be zero at some point without the goto having finished. Beware!

© 2005 AWR Technology