The ASCOM driver for ServoCAT, developed by Peter Eschman
What are the significant features of the ASCOM ServoCAT v5.2.1 Driver?
This ServoCAT ReadMe file covers what is needed to run the ASCOM ServoCAT v5.2.1 Driver under the supporting framework of ASCOM Platform v6.1 SP1. The ASCOM ServoCAT v5.2.1 Driver has been written to the ASCOM v2 Telescope Specification, which replaced the earlier v1 specification. ASCOM Platform versions higher than v4.1 no longer include telescope drivers, so telescope drivers need to be installed using stand-alone installers. ServoCAT_Driver_v521_Setup.exe is a stand-alone installer for this telescope driver, which is compatible with ASCOM Platform v5.5 and higher.
1) The driver is aware that your ServoCAT + Argo Navis uses the ICRS/Airless coordinate reference frame, and if asked, can report this to the planetarium software as J2000 with no refraction correction. If the planetarium software asks the driver for the coordinate reference frame, it may be possible to avoid errors due to miss-matched coordinate corrections.
2) The driver can report Sidereal time to the planetarium software if the user has properly set their observing site longitude in the driver setup screen. When the driver reports Sidereal time, it is based on the computer clock and the user specified longitude. Sidereal time is not derived from the Argo Navis, so settings for date and location in the Argo Navis do not affect the driver.
It is up to the planetarium software to take advantage of this information provided by the driver. Typically, the user must tell the planetarium software their site elevation, latitude and longitude. If you suspect problems with Sidereal time you should check your planetarium software settings first, then verify that your location value is correct on the driver setup screen.
In at least one case, planetarium software is known to query the ASCOM driver for observing site latitude and longitude, and then set the observing location to these retrieved values, overriding any other user supplied settings. You are strongly advised to be sure your site location values are correctly set in the driver settings screen.
3) The driver supports serial connections on COM1 through COM16
4) The driver supports Windows language settings that use a comma as decimal symbol and a period as digit grouping symbol.
5) The diver supports expanded setup values for site location, mount type and optics. For more information on setup values please see ServoCAT Driver.htm, which you can access by way of the help button on the driver setup screen.
6) Position polling is throttled to no more than twice per second to reduce loading on the serial port and command processing.
7) The driver can Sync between the planetarium software and the ServoCAT, allowing screen cursor position to be matched to what you see in the eyepiece.
8) This driver version fixes issues with a hand pad initiated spiral search, latency in position refresh, detection of GoTo completion, and detection of GoTo request that exceeds slew limits that were found in v4.4.3 of this driver.
9) This driver has the ability to convert between Apparent Coordinates used by some older planetarium programs to ICRS/Airless (J2000 with no refraction correction). Please see the ServoCAT Driver.htm file for more details on coordinate conversion. The driver help file should be located in the same directory with ServoCAT.dll, which is usually \Program Files\Common Files\ASCOM\Telescope. The driver help file can be accessed through the help button on the driver setup screen. View Driver Help File
10) If you have a previous version of the ServoCAT driver installed, you may wish to uninstall it before installing a new version. There is no harm in leaving an old version, since all important files are overwritten and a new version will re-use any applicable driver parameters. If you do not uninstall a previous version, two or more entries for the ServoCAT driver may show in your Control Panel, Add/ Remove programs. If you uninstall a previous version, you will need to reset your driver setup values, since they will be deleted during the uninstall process.
11) When combined with revised firmware in your ServoCAT and Argo Navis (released in May 2012 or newer), this driver can run in higher resolution. Higher Resolution position feedback to the planetarium program improves resolution to 0.36 arc seconds (note this is an increase in resolution - not accuracy). Higher Resolution also is used for Goto commands from the planetarium program. Please note that High Resolution mode requires newer Argo Navis firmware (v0.6.56 or newer) along with ServoCAT firmware (SR61B or newer).
12) The only change to the v5.2.0 driver, released December 2014, has been a patch to allow southern hemisphere latitudes to be maintained correctly. This has resulted in v5.2.1 driver, released June 2015.
As of December 2014, you can get the most functionality from this ASCOM ServoCAT v5.2.x driver if it is used along with ServoCAT firmware v70A or higher and Argo Navis firmware v3.0.0 or higher. When coupled with the newest firmware versions, in addition to High Resolution, the following features are also supported:- The ability to Park the scope. The scope returns to the power up position in both axes. Please note that if you have moved your telescope manually, using clutches to bypass the drive motors, Parking the scope will return to your motor power up position, which is no longer in sync with where the telescope is pointing when you try to Park. This may move the scope into a dangerous position! When you have used this driver to park your scope, tracking is turned off for both axes. After parking your scope, you must unpark it to request any other actions.
Care has been taken to assure that this driver works with both earlier and revised firmware versions. In Legacy mode, you will lack the new features listed in this section, however you will gain the coordinate conversion capability outlined above in section 9). Although current firmware versions are recommended for use with this ASCOM ServoCAT v5.2.1 driver, this driver version will run very well with earlier firmware versions in your ServoCAT and Argo Navis. With older firmware, the driver will simply lack some of the newer functionality outlined in this document.
What is ASCOM?
The Astronomy Common Object Model (ASCOM) is an interface used by low-level telescope "driver" components. ASCOM also supports low-level drivers for focusers, cameras, filter wheels, rotators and dome control. More details can be found at ASCOM-Standards.org and here Wikipedia entry. General questions about ASCOM may be covered in this Yahoo newsgroup ASCOM-Talk, however, specific questions related to a given driver should first be referred to the author of that driver.
Platform versions earlier than v6.1 SP1 are no longer officially available from the ASCOM web site and are not officially supported by ASCOM support volunteers. Earlier Platform versions may be available from unofficial sources. Platform versions 5.x and newer rely on .NET runtime support files. Operating Systems (OS) levels offer different compatibility with various .NET releases. Here is a brief summary of the relationship between platform version and OS version: Platform v4.x works with OS prior to Windows 2000, and may work with newer OS versions. Platform v5.x works with Windows 2000, and may work with some newer OS. Platform v6.x works with Windows XP, Vista, 7 and 8 in both 32 and 64-bit modes. At this time, the most current ASCOM Platform is v6.1 SP1. Please note that telescope driver version numbers do not necessarily correlate with Platform version numbers.
What software supports the ASCOM driver for ServoCAT?
Since many planetarium software programs now support ASCOM, they also support the ASCOM ServoCAT driver. A variety of commercial, shareware and free programs are available. If you are looking for such a program, you might want to consider Cartes du Ciel (Sky Charts), written by Patrick Chevalley. Patrick offers current release versions for Windows, Linux and Mac OS, and is actively developing new releases with extended features. It is available free from: http://www.ap-i.net/skychart/index.php
Another free planetarium software option is C2A (Computer Aided Astronomy) available here: http://www.astrosurf.com/c2a/english/index.htm
What do I need to control the ServoCAT from my computer?
Planetarium software initiated GoTo requires Argo Navis firmware v0.6.12 or higher. To check your Argo Navis, go to Mode Status, and rotate the dial knob to see Status Version, Version=0.6.12 (or higher) If you are flashing the Argo Navis to update the firmware, please follow the instructions carefully to avoid damaging the Argo Navis. Please contact Gary Kopff of Wildcard Innovations Pty. Ltd. for details on how to perform a safe firmware upgrade.
One new step is needed with the Argo Navis: you must select Mode Catalog, From Planetarium. This setting will allow the planetarium software to request that a GoTo operation be performed by the ServoCAT and Argo Navis hardware.
The planetarium software typically connects to the ServoCAT serial port (located on the left side of the Gen1 ServoCAT controller). Use the cable labeled "ServoCAT Serial Adapter" to connect to the 9-pin serial port on your computer. A wireless serial connection is recommended to eliminate the need for a cable running from the computer to the ServoCAT. Another option is to mount your laptop computer so that it is directly attached to the scope. A final option is to use a hand-held computer, smart phone or tablet that is mounted on the scope or connected by a wireless link.
Newer ServoCATs come with USB ports, rather than Serial ports. Please follow the ServoCAT documents included with your hardware for instructions on how to connect cables to these newer units.
More recent smart phones and tablets may support your ServoCAT/Argo Navis hardware. These devices typically run iOS or Android operating systems that do not use ASCOM. These devices access your telescope hardware by way of native commands, so functionality can vary widely between various products. At least one software (Sky Safari) has native support for ServoCAT on Android, iOS, and MacOS.
Although the ServoCAT command set is based on commands used by the original Sky Commander, your ServoCAT can use additional commands to support GoTo and other features. If you select Sky Commander protocol in your planetarium software, you may lack support for GoTos and only see a telescope cursor on screen. An on-screen telescope cursor will indicate where the telescope is pointing, and the pointer should reflect the fact that the scope is tracking. The ASCOM ServoCAT driver provides for the full command set used by the ServoCAT, including the GoTo command.
I have heard that newer Sky Commander units do support GoTos initiated from planetarium software. If so, then the ASCOM ServoCAT driver will work with this hardware combination. If the planetarium software setting for Sky Commander does not offer all the features you expect, you may want to try the ServoCAT setting for telescope control with this combination.
The ASCOM driver is not compatible with older hand-held computers because they run Palm, PocketPC or other operating systems. I am told that one or more planetarium programs for Palm do have native support for the ServoCAT. TheSky Pocket Edition, which runs on the PocketPC operating system, may only offer support via the Sky Commander setting, which may be missing GoTo command support. You will need to use the latest HotFix to get correct telescope cursor position on screen for TheSky Pocket Edition. A telescope cursor on screen is a telescope location indicator, which usually takes the form of a cross-hair. I tested TheSky Pocket Edition v1.10.011, and the on-screen telescope cursor did work correctly, while the GoTo command was not supported at that time. A few years ago, the authors of TheSky Pocket Edition indicated that they were adding the GoTo command for ServoCAT.
How do I use the ASCOM driver for ServoCAT?
1) Download the ASCOM Platform from http://ascom-standards.org. At present, the current version of ASCOM for Windows XP or higher is Platform v6.1 SP1. Download and install ASCOM Platform61SP1.exe. Platform versions earlier than v6 are no longer officially available from the ASCOM web site and are not officially supported by ASCOM support volunteers. See What is ASCOM? for details. Earlier Platform versions may be available from unofficial sources. Both ASCOM Platform v6.1 SP1 and ServoCAT driver v5.2.1 are compatible with Windows running in 64-bit mode.
The stand-alone ServoCAT_Driver_v521_Setup.exe driver installer will check for and require Platform version 6.x or higher during the install process. If you have an earlier Platform version that is appropriate for your OS level, I may be able to offer help installing this driver. My help with earlier Platform versions will be handled on a case-by-case basis. If you have Platform v4.1, you may be limited to running the older driver v4.2.2, which is distributed as part of Platform v4.1.
2) The second step is to install the planetarium software of your choice that supports ASCOM. Please see the Software section above, for some free software options that support ASCOM.
3) Install any required ASCOM support files for your planetarium software. See The ASCOM download area for plugins.
4) The next step is to download this ReadMe file:
Followed by the current Stand-alone ASCOM ServoCAT driver installation for ASCOM Platform v5 and higher:
Please note that this ReadMe file, as well as the Driver ReadMe file are included in, and installed by ServoCAT_Driver_v521_Setup.exe
This Stand-Alone installer is required for all platform versions higher than v4.1. Since most people will have downloaded and installed Platform v6.1 SP1, your next step is run "ServoCAT_Driver_v521_Setup.exe" to install the ServoCAT ASCOM driver.
The install process will place ServoCAT.dll and ServoCAT htm document files
in the default install location:
\Program Files\Common Files\ASCOM\Telescope for 32-bit systems and
\Program Files (x86)\Common Files\ASCOM\Telescope for 64-bit systems.
5) OK, hopefully we got to this step after installing the appropriate ASCOM Platform and the ASCOM ServoCAT v5.2.1 driver is now installed. The next step is to start up your planetarium software and select ASCOM under telescope type or telescope interface.
6) Select Telescope Settings or Configuration.
7) Select ServoCAT in the ASCOM Telescope Chooser.
8) Select Properties and verify your serial port choice is correct. At this time you should enter your site location, optics characteristics and mount type. More information is available by clicking the help button, which will bring up ServoCAT Driver.htm. The driver help file should be located in the same directory with ServoCAT.dll, which is usually \Program Files\Common Files\ASCOM\Telescope. Click here to view Driver Help File. When you are done with the settings, click the OK button. For more information on some of these settings, see the following section What if GoTos are not as accurate as I would like?
9) Turn on your ServoCAT and align your scope using your normal stand-alone procedure. Once your ServoCAT is aligned, set your Argo Navis to Mode Catalog, From Planetarium. Next, go to your planetarium software and select "Telescope Connect" or "Establish Link". Once the connection is established to your ServoCAT, your telescope position should be showing on your computer screen as a telescope cursor or cross-hair. You should now be able to command the ServoCAT to GoTo objects by selecting them from your computer planetarium software.
A few tips:
Be sure to review the section What do I need to control the ServoCAT from my computer?, to verify you have the correct firmware for your Argo Navis, and that you have Catalog: "From Planetarium" setting selected.
Remember to select "Disconnect" or "Terminate Link" in your planetarium software prior to exiting your planetarium software, or you will probably cause your serial port connection to hang. If the serial port connection hangs, your computer system may become unresponsive. Unfortunately, if this happens, you often may need to close your planetarium software and restart it, in order to re-establish a link to your ServoCAT
I have seen situations, when using a USB to serial adapter, where the telescope connection can only be established once per software session, and subsequent attempts may require that you restart your planetarium software.
As future versions of this driver are released, it will only be necessary to run a new stand-alone installer to copy the new version of the driver to the appropriate location. Updates to the ASCOM platform may also be required in future.
This version of the ASCOM driver for ServoCAT has been successfully tested in SkyTools v3.2 as well as Cartes du Ciel (Sky Chart) v3.4.1, AstroPlanner v2.0 and TheSky v220.127.116.11. This driver may also work well in earlier versions of these products. As I indicated earlier, any software that correctly supports ASCOM should work fine with the ASCOM ServoCAT v5.2.1 driver.
Native support for ServoCAT is implemented for TheSky v.6 if you are running v18.104.22.168. I believe that TheSky X also includes native support for ServoCAT. Native support for ServoCAT is available in Sky Safari, which currently runs on Android and iOS devices. Native support does not make use of ASCOM, so this ASCOM ServoCAT driver is not part of the mix for ServoCAT control by way of native commands.
If you wish to use ASCOM with TheSky v5 or v6, please be sure you have followed the proper steps to install the ASCOM version of TeleAPI.dll in the appropriate directory. See The ASCOM download area for plugins and use "TheSky™ ASCOM Telescope (TeleAPI) Plug-In for TheSky 5/6 (5.0.4)". Similar plugins are available for TheSky X as well as software from other vendors
ServoCAT Utility Program: SCU.exe
SCU is a command line utility that can be run interactively or from a simple batch file that you can use in scripts or scheduled jobs. You must disconnect the ASCOM driver from your ServoCAT before running SCU, and you must quit SCU before running the ASCOM ServoCAT driver. This is required because only one application can use your ServoCAT USB/Serial Port at any given time. SCU is not an ASCOM-aware application, so it can not be used with an ASCOM hub like POTH. SCU offers the following capabilities:
You can download a copy of SCU.exe here SCU.exe and can find the doc file for SCU here SCU_ReadMe.pdf
What if GoTos are not as accurate as you would like?
Your GoTos will be no more accurate when initiated from planetarium software than they are when started from the ServoCAT hand pad. A careful initial alignment and use of correct setup values in the Argo Navis and ServoCAT are always critical for accurate GoTos. Any additional aligns or syncs that alter what you see in the eyepiece must be done using the Argo Navis, since planetarium software based aligns and syncs are not communicated back to the Argo Navis.
As noted above in What's New 7) , this version of the driver supports Sync internal to this driver. You can click on Sync in your planetarium software and the ServoCAT position displayed on screen will move to the Sync point. This should make it possible to have the object you have centered in the eyepiece agree with your on-screen telescope cursor position.
There are a few issues that might make planetarium software GoTos appear to be less accurate than those initiated by the ServoCAT hand pad. The ServoCAT+Argo Navis hardware pair sends and receives coordinates in the ICRS/Airless reference frame (J2000 with no refraction correction). Planetarium software can correct these coordinates for precession to the current day as well as performing adjustments for nutation, aberration and refraction. The net result of all of these corrections is that the coordinates get transformed into what may be called the local Topocentric reference frame, sometimes called Epoch of Date (EOD, or JNow).
Some planetarium software convert to Local Topocentric or Apparent coordinates before sending to the telescope (or ASCOM ServoCAT driver). TheSky planetarium software may be one example of software that converts to Apparent coordinates. This discrepancy in coordinate systems (often called Epoch of Date or EOD) can contribute to on-screen representations that do not match what you are seeing in the eyepiece. This can also be the source of frustrating discrepancies in scope movement when executing very short slews, as is sometimes the case when using a software based hand pad to move your scope.
If the planetarium software chooses to ask, this version of the driver can inform the planetarium software that it uses J2000 coordinate reference frame. If your planetarium software is correcting for refraction, you may want to turn off the planetarium refraction correction so that you match the coordinates that the Argo Navis is sending and receiving. Turning refraction correction on or off in the Argo Navis may change what you see in the eyepiece, but it will not change the coordinates that are received from or sent to your planetarium software. Refraction correction is likely to be the biggest of all four types of correction, so it will have the largest influence on any a disagreement between what you see in the eyepiece and what you see on-screen. Refraction correction will have the biggest effect on objects that are low in elevation and closer to the horizon, where atmospheric refraction is greater because you are looking through more air.
The net result of double corrections for coordinate systems and refraction may be that the GoTo is slightly less accurate, or that the on-screen representation shows the telescope slightly off center from the object, even when the object is centered in the eyepiece. First search out and confirm your planetarium software settings related to coordinate system, precession, nutation, and refraction and confirm that they are set correctly. Be sure to try the driver-based Sync capabilities outlined earlier to see this will help in this situation.
Starting with version 4.5.1 of the ASCOM ServoCAT driver, the driver has the ability to convert between Apparent Coordinates and the ICRS/Airless reference frame (J2000 with no refraction correction) What's New 9).
A good reference for a discussion of the various coordinate systems is "Mean and Apparent Place Computations in the new IAU System. III. Apparent, Topocentric, and Astrometric Places of Planets and Stars", Kaplan et. al., April 1989.
Extensive trouble shooting tips are beyond the scope of this basic ReadMe file, but I can offer a few suggestions:
- You suspect a problem with ASCOM.
Try selecting the Telescope Simulator in place of ServoCAT in the ASCOM chooser. This will allow you to use a simulated telescope, and confirm that all of the basic pieces and software connections between ASCOM and your planetarium software are working correctly. Note that the Telescope Simulator offers functionality beyond that of the ServoCAT driver, so its capabilities will not be an exact match to your ServoCAT. Using the Telescope Simulator can be a great way to explore the capabilities of your planetarium software, and let you gain confidence in how to use it to suit your needs. You can do this with the Telescope Simulator without wasting precious dark sky time! There is a tendency to try to uninstall and then reinstall software when problems are suspected. This rarely does any good, and can often complicate steps that are required to fix a problem.
- You are seeing an error message during the install or connect steps.
The first thing to do is to write down the full error message, including the header label of the error message box. Next, you may be able to do a web search on that error message to see what others have done to fix the error. With Windows Vista or 7 it may prove useful to run the software using Administrator rights or use XP compatibility mode. Sometimes this is only necessary the first time the software is invoked, and subsequent software runs can use lower privilege levels.
- You think your connection is good, but you still can not get the
planetarium software to connect?
You may want to add an intermediate software piece between your planetarium software and the ServoCAT driver. Just like the Telescope Simulator mentioned above, the Plain Old Telescope Handpad (POTH) comes with the ASCOM Platform. Start up POTH (Start menu, Programs, ASCOM Platform 6, Scope-Dome Hubs, POTH) then use the POTH Setup button, Choose Scope to start the ASCOM chooser and select ServoCAT. Next, start up your planetarium software and use the ASCOM chooser to connect to POTH. POTH acts as a Hub, so it is possible to connect multiple pieces of software to POTH at the same time that POTH is connected to the telescope (ServoCAT) driver. With POTH in the mix, several software pieces can talk to your ServoCAT at the same time. POTH has an option to display traffic, so you can see what types of requests are coming from your planetarium software. You can also set POTH to the Telescope Simulator if you want to test how things can work together. POTH can also make motion control buttons available that can be used to move your ServoCAT in defined increments. Be sure the "Motion Controls" box is checked on the POTH Setup screen (this box is located just above the "OK" button). Other techniques are available for logging serial port traffic, and more details are available on request.
- You are unable to connect to the COM port used by your ServoCAT.
USB to Serial adapters are notorious for causing this type of problem. It is not uncommon for an adapter to work with one piece of software, but not another. This happens because software can access the serial port functions in a variety of ways. Cheap USB to Serial adapters should be avoided. One brand that seems to work well for many people is the adapter offered by Keyspan. It can cost a bit more than others, but can be obtained at a discounted price from some vendors. It comes with good diagnostics, and will always use the same COM port number, regardless of the USB port that is used.
Please note that COM port support routines in ASCOM Platform 6 or higher rely on underlying .NET serial port access. In some cases, this has revealed a weakness in the implementation of the serial port used by some inexpensive USB to serial port hardware. In these cases, replacing the adapter with a higher quality device often solves many connectivity issues. It makes little sense to entrust control of your expensive telescope (and your valuable time) to a cheap and unreliable USB to serial adapter.
Please be aware that most USB to Serial adapters will assign a new COM port number every time they are plugged into a different USB port. This can cause you to run out of COM port numbers, and you will have to take steps to delete the unused port designations to free up a lower COM port number. With these adapters, ALWAYS use the same physical USB port. Some people seem to have good results with adapters that use the FTDI chip set. A miss-wired or defective cable will also cause connection failures. You may wish to check Tom Hilton's helpful tips on Checking and setting Com Ports and Show allocated COM Ports
- COM port is in use.
Microsoft ActiveSync is used to communicate with WinCE/Pocket PC devices. Microsoft ActiveSync is known to tie up the COM port, so if you are using it you might want to locate and download the utility called Kill ActiveSync, which will prevent ActiveSync from loading at boot time. Alternatively, you can run task manager, and stop the process called WCESCOMM.EXE. Also check to be sure you are using the correct COM port.
Comments or questions?
Contact Gary Myers at StellarCAT http://www.stellarcat.com, Contact Gary Kopff at Wildcard http://www.wildcard-innovations.com.au ), or you may contact me at firstname.lastname@example.org or check http://www.unm.edu/~eschman
This driver is based on a variety of ASCOM source code authors and developers. Sometime around 2003, Robert B. Denny wrote the original ASCOM telescope driver template, and Douglas George modified it for Sky Commander, so that the telescope position would be displayed on the planetarium software screen. I released the first incarnation of the ASCOM ServoCAT driver in 2004, at which time I also used portions of code from two other drivers to enable the ServoCAT GoTo command, including the AstroOptik driver, developed by Robert B. Denny, and the SS2K driver, developed by Arne Danielsen.
As development proceeded over the years, I've used portions of code from the Celestron driver by Chris Rowland to help bring the driver up to the v2 Telescope Specification as well as many other later improvements. Tim Long has shared some useful tips he learned from his recent work updating the Meade ASCOM driver. I found the ASCOM Conform tool, written by Peter Simpson to be very valuable way to evaluate my many revisions to the ServoCAT driver. Peter Simpson also provided invaluable assistance in implementing Astrometry.Transform (which he contributed to ASCOM). This driver can use these transforms to convert between coordinate systems. I would like to thank all of these people for sharing their source code, tools, knowledge, and support, all of which has helped to make this project successful.
I would also like to thank Gary Myers of StellarCAT, and Gary Kopff of Wildcard Innovations Pty. Ltd., for their encouragement to develop and extend this driver.
Thanks for using this driver, and I hope it helps you go to many wonderful objects!
Peter Eschman, email@example.com