The ASCOM driver for ServoCAT, developed by Peter Eschman, 04/11/04
What is the difference between the ASCOM ServoCAT Driver v3.0.11 and v4.2.2?
The ASCOM ServoCAT Driver v4.2.2 has been written to comply with the ASCOM V2 Telescope Specification. The ASCOM V2 Telescope Specification replaces the V1 Specification, and will be used by newer ASCOM telescope drivers. Some of the drivers that are part of the new ASCOM V4 Platform follow the ASCOM V2 Telescope Specification. The main implications for the ServoCAT implementation are:
1) The driver is now aware that the ArgoNavis uses the J2000 coordinate reference frame, and if asked, can report this to the planetarium software.
2) The driver can now be told whether or not the ArgoNavis is set to do refraction correction, and if asked, can report this status to the planetarium software. This setting is done on the driver setup screen.
3) The driver can now report Sidereal time to the planetarium software, if the user has properly set their longitude in the driver setup screen. When this driver reports Sidereal time, it is based on the computer clock and the user specified longitude. Sidereal time is not derived from the ArgoNavis, so settings for date and location in the ArgoNavis are not used.
It is now up to the planetarium software to take advantage of this new information. Typically, the user must tell the planetarium software their site elevation, latitude and longitude, so this should be checked in the planetarium software first, if there are any suspected problems.
If the planetarium software asks the driver for the coordinate reference frame and the status of refraction correction, it may be possible to avoid correcting twice for these values.
4) The Readme file has been converted to HTML, and a smaller HTML help file is now accessible from the driver setup screen.
5) A newer version of Astro32.dll (02/02/2004) is included.
6) This version of the ServoCAT ASCOM driver supports COM1 through COM16
What is ASCOM?
The Astronomy Common Object Model (ASCOM) is an interface used by low-level telescope "driver" components. More details can be found at http://ascom-standards.org/
What software supports the ASCOM driver for ServoCAT?
Many planetarium software programs now support the ASCOM Platform,
so 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),
available free from http://www.astrosurf.com/astropc. This program is
written by Patrick Chevalley, and the current version is 2.75.1. You
will need to download two files to get started:
- cdcin275.zip (15MB)
- cdcascom.exe (366k)
You may also want to download ciel2751.zip (1.3MB) to update from v2.75 to v2.75.1
What do I need to control the ServoCAT from my computer?
Please note that planetarium software initiated GoTo will require ArgoNavis firmware v0.6.12 or higher. As of 10/03/04, this is available as a beta version from Gary Myers at StellarCAT. To check your ArgoNavis, go to Mode Status, and rotate the dial knob to see Status Version, Version=0.6.12 If you are flashing the ArgoNavis to update the firmware, please follow the instructions carefully to avoid damaging the ArgoNavis. Please contact Gary Myers for details on how to perform a safe firmware upgrade.
One other step is needed with the proper firmware in the ArgoNavis, and that is to select Mode Catalog, From Planetarium. This setting will allow the planetarium software to request that the GoTo operation be performed by the ServoCAT and ArgoNavis hardware.
Typically, the planetarium software is connected to the ServoCAT serial port (on the left side of the 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 that is mounted on the scope or connected by a wireless link.
The ASCOM driver is not compatible with hand-held computers because they run the Palm or PocketPC operating system. 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, only has support via the Sky Commander setting, so it is currently missing the GoTo command. 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 does work correctly, while the GoTo command is not yet supported. The makers of TheSky Pocket Edition have indicated that they are currently working to add the GoTo command for ServoCAT.
Although the ServoCAT command set is based on commands used by the Sky Commander, the ServoCAT uses an additional GoTo command. This means that if you simply select Sky Commander protocol in your planetarium software, you can only expect to get a telescope cursor on screen, and you will be lacking support for GoTos. A telescope cursor on screen 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.
How do I use the ASCOM driver for ServoCAT?
1) First, download the current ReadMe file from:
http://www.unm.edu/~eschman/ServoCAT ReadMe.htm
2) Second, install the planetarium software of your choice that supports ASCOM.
3) Install any needed ASCOM support files for your planetarium software, for example, cdcascom.exe for Cartes du Ciel (Sky Charts).
4) Next, download ASCOM from http://ascom-standards.org. At present, the current version of ASCOM is the V4 Platform, which is a ~14689kb download. The ASCOM ServoCAT driver v4.2.2 is part of the V4 ASCOM Platform. I strongly recommend that you install the V4 ASCOM Platform, even if you have already installed the V3 ASCOM Platform. If you already installed the V3 ASCOM Platform, do not un-install it, just proceed with the V4 Platform install. During the install of the V4 Platform, you can skip the option to install the source files, since you already have the ReadMe file you downloaded in step 1).
Once you have downloaded and installed the V4 ASCOM Platform, the
ServoCAT driver will be automatically installed. The V4 ASCOM Platform
install will place ServoCAT.dll and ServoCAT Driver.htm files in the
default install location, which is:
\Program Files\Common Files\ASCOM\Telescope.
If you install the full
version with source, an earlier, out of date version of ServoCAT
ReadMe.htm (this file) will be installed in:
\Program Files\Common Files\ASCOM\Telescope\Source\ServoCAT Driver.
5) OK, hopefully we got here after we installed the V4 ASCOM Platform. The next step is to start up your planetarium software and select ASCOM under telescope type or telescope interface.
6) Select Settings or Configuration.
7) Select ServoCAT in the ASCOM Telescope Chooser.
8) Select Properties and verify the correct serial port. At this time you can also set the status of refraction correction, and enter your site longitude. More information is available by clicking the help button, which will bring up ServoCAT Driver.htm. This help file should be located in the same directory with ServoCAT.dll, which is usually \Program Files\Common Files\ASCOM\Telescope. When you are done with the settings, click the OK button. For more information on some of these settings, see the section "What if GoTos are not as accurate as I would like?" in the following text.
9) Turn on your ServoCAT and align your scope using the normal stand-alone procedure. Once your ServoCAT is aligned, set your ArgoNavis (firmware v0.6.12 or higher) 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 you should see the telescope position showing on your computer screen, and you should be able to command the ServoCAT to GoTo objects by selecting them from your computer planetarium software.
10) Enjoy
Be sure to review the section
What do I need to control the ServoCAT from my computer?
to be sure you have the correct firmware for your ArgoNavis, and that
you have the correct "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.
In the future, if newer versions of this driver greater than v4.2.2 are released, it may only be necessary to copy the newer versions of ServoCAT.dll and ServoCAT Driver.htm file to the original install location. Because version v4.2.2 of the driver has been locked into binary compatibility mode, it may not be necessary to re-run any driver registration.
So far, the ASCOM driver for ServoCAT has been successfully tested in TheSky v5.00.105 through v5.00.108 as well as Cartes du Ciel (Sky Chart) v2.75 and v2.75.1. As of 09/07/04, the latest HotFix for TheSky v.5 is v5.00.108. Native support for ServoCAT has been implemented for TheSky v.6 by way of a HotFix that you will need to download from TheSky web site. You can also use the ASCOM driver for ServoCAT in TheSky v.6. As I indicated earlier, any software that correctly supports ASCOM should work just fine with the v4.2.2 driver for ServoCAT.
If you are installing into TheSky v5, or installing ASCOM into TheSky v6, please see Detailed instructions, installing the ASCOM ServoCAT driver in TheSky v5.
What if GoTos are not as accurate as I would like?
First of all, your GoTos will be no more accurate when initiated from planetarium software than they are when started from the ServoCAT hand pad. A careful alignment and use of correct setup values in the ArgoNavis and ServoCAT are still critical for accurate GoTos. Any additional aligns or syncs must be done using the ArgoNavis, since planetarium software based aligns and syncs are not communicated back to the ArgoNavis.
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 ArgoNavis expects to get coordinates in the J2000 reference frame. The ArgoNavis then corrects these coordinates for precession to the current day as well as performing adjustments for nutation, aberration and refraction (if you have turned on refraction correction). The net result of all of these corrections is that the coordinates get transformed into what is called the local topocentric reference frame.
Some planetarium software convert to local topocentric coordinates before sending to the telescope (or ASCOM ServoCAT driver). In these cases, since the ArgoNavis is also performing the same transformations, the coordinates may be double corrected. TheSky planetarium software is one example of software that converts to local topocentric coordinates.
As indicated at the beginning of this document, the ASCOM ServoCAT driver v4.2.2 can inform the planetarium software that it uses J2000 coordinate reference frame, if the planetarium software chooses to ask. It can also notify the planetarium software, if asked, what the current status is for refraction correction. Since the ASCOM V2 Telescope Specification is new, it may take some time for planetarium software to take advantage of these features. So, for now, if your planetarium software is correcting for refraction, you should turn off the refraction correction in the ArgoNavis, and indicate that it is turned off on the setup screen for the ASCOM ServoCAT driver. Refraction correction is likely to be the biggest of all four types of correction, so it will have the largest influence on loss of accuracy in a GoTo. The refraction correction will have the biggest influence with objects that are low and thus closer to the horizon.
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.
Comments, Questions?
Contact Gary Myers at StellarCAT (RXDesign@ssvecnet.com, http://www.stellarcat.biz/) or you may contact me at eschman@unm.edu or check http://www.unm.edu/~eschman
Problems connecting to the COM port?
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.
Detailed instructions, installing the ASCOM ServoCAT driver in TheSky v5
1) install the ASCOM V4 Platform
2) be sure to copy TeleAPI.dll from
\program files\Common Files\ASCOM\Telescope\Planetarium\TheSky
to
\program files\Common Files\System
for the V4 ASCOM Platform, TeleAPI.dll is 60k dated 11/25/04 3:26 P.M.
At one point I got instructions indicating that this dll would need to be recopied after installing a HotFix patch for TheSky, but this was not needed after installing the v5.00.102 patch.
4) install ASCOM driver for ServoCAT using the instructions above
3) choose the ServoCAT option under
Telescope
-Telescope Setup
--Telescope API
---Settings
----ASCOM Telescope Chooser
-----Properties
------Select correct serial port and other properties, baud rate is fixed at 9600
Credits
This driver is based on ASCOM source code from Robert B. Denny, who wrote the original driver template and Douglas George, who modified it for Sky Commander so that the telescope position would be displayed on the planetarium software screen. I also used portions of code from two other drivers to enable the ServoCAT GoTo command: the AstroOptik driver, developed by Robert B. Denny, and the SS2K driver, developed by Arne Danielsen. I used portions of code from the Celestron driver by Chris Rowland to help bring the driver up to the V2 Telescope Specification. I found the ASCOM Telescope Validator tool, written by Peter Enzerink to be very valuable way to evaluate the revised ServoCAT driver. I would like to thank all of these people for sharing their source code, tools and knowledge, which make this project possible.
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 trying this driver, and may it help you go to many wonderful objects!
Peter Eschman
You may contact me at eschman # unm * edu