Controlling the EQ6 mount directly from a PC - EQMod
The EQ6 SkyScan controller has a fairly minimal feature set - for the most part the included features are perfectly adequate and in use, the system works very well, locating objects from the built in database and tracking them accurately within the limits of the mounts mechanical hardware but there are a couple of omissions that would really make the system better. The very latest version of the hand controller which has upgradeable firmware addresses these omissions to some extent but the cost of an updated hand controller is out of proportion to advantages of upgrading and I have the original hand controller which is not firmware upgradeable.
Major Missing Features
- No SYNC command
- No NUDGE command via PC control
- No GPS Support
Minor Missing Features
- Date lost at turnoff
- Time lost at turnoff
- Daylight Saving Data lost at turnoff
The EQMod Solution
Luckily, there is a really good group of people working on an open source solution and it is available free of charge.
I am currently a beta tester for the group and although I do not currently contribute from a software generation point of view I report bugs and operational problems to the group and make suggestions for possible improvements. My 'fixed location' really helps here as I am in a position to carry out various tests on different days from a 'known' start point!
The EQMod solution comprises of a simple hardware interface and an ASCOM driver. In addition, there are several diagnostic tools for testing new developments.
All the commands to control the mounts controller board are output via an RS232 Serial Port but with the hand controller removed, there is no serial connector for the mount! However, there is a TTL interface on the mount controller board accessible via the 9 pin D Socket on the faceplate of the mount and this is the way into the system! A very simple serial to TTL adapter can be homebuilt or bought commercially.
The interface is a very simple design that takes its power from the mount itself. This 12v supply is reduced and regulated to 5v by a 7805 voltage regulator to power the converter. The RS232 signal from the PC is then converted to TTL levels (and vice versa) by an EIA RS232 converter.
Building the required circuit board is not a difficult task if you can solder and work methodically but ready built solutions are also available. Amazingly, I happened to have a suitable interface in my junk box left over from a previous project! Shoestring Astronomy make one, details here:- http://www.store.shoestringastronomy.com/products_eq.htm
The photograph below shows my own solution
Before a suitable ASCOM driver can be loaded it is necessary to install the ASCOM Platform. This is a set of interface standards for scriptable or programmable low level control of astronomical instruments and related devices and the individual equipment drivers interface with the equipment via this platform. More information about the ASCOM Platform can be seen here:- http://ascom-standards.org/index.html
The ASCOM Platform itself can be downloaded from here http://ascom-standards.org/downloads.html
This driver has been developed by the EQMod Group who can be found at this Yahoo Tech Group address:- http://tech.groups.yahoo.com/group/EQMOD/
The EQMOD ASCOM Driver uses EQCONTRL.DLL to communicate with the stepper motor controller board and with the EQMOD ASCOM driver, the user will be able to control a modified EQ6 mount using any ASCOM compliant planetarium software at 0.144 arcsecond resolution.
The driver supports almost all of the ASCOM methods and properties which include:-
- GOTO/SLEW at 0.144 resolution (depending on the accuracy of the planetarium database)
- SYNC (via ASCOM / Planetarium Software)
- PARK TO HOME/PARK TO CURRENT/UNPARK
- 1 STAR ALIGNMENT (2-STAR, N - STAR to follow)
- PULSEGUIDE (at variable speed rates and with 'duration' parameter support and duration override)
Other Functions include:-
- SIDEREAL, LUNAR and SOLAR TRACKING
- AUTOGUIDER PORT SPEED RATE SETTING (RA and DEC speeds can be set independently)
- VARIABLE SLEW SPEEDS which can be set from x1 to x800 of the sidereal rate
- NORTH and SOUTH Hemisphere support
- EQMOD SLEWPAD Interface that allows a three button mouse as a SLEW HAND PADDLE.
- JOYSTICK SUPPORT for Hand control of the Telescope Slew
- NUMERICAL KEYPAD SUPPORT for Hand control of Telescope Slew
- GPS SUPPORT for Time and Location Synchronisation
Functions that will be supported (currently under development):-
- PEC TRAINING (via hand control or PULSEGUIDE sequence) AND PLAYBACK (encoder position accurate)
- BACKLASH COMPENSATION (currently not active since most of the EQ designs does not require backlash compensation)
- USER PROGRAMMABLE TRACKING RATES (both on DEC and RA)
- 2 - STAR and N - STAR ALIGNMENT
Such is the success of this project that I have not used the SkyScan Hand Controller since the beginning of December, 2006 and can see no reason why I should ever need to again and I have successfully implemented all the currently available features and currently use a wireless mouse for slewing and fine adjustments and have just finished implementing Pulse Guide autoguiding - fantastic!
PLEASE NOTE THAT ANY MODIFICATIONS THAT YOU MAKE TO YOUR OWN MOUNT ARE MADE ENTIRELY AT YOUR OWN RISK AND COULD VOID YOUR WARRANTY!