USB Guide Port Adapter User Manual
USB Guide Port Adapter
User Manual
Revision 1.2
Copyright 2005-2006, Shoestring Astronomy
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The Shoestring Astronomy USB Guide Port Adapter is designed to allow personal
computers to control ST-4 compatible autoguider ports as found on many telescope
mounts. Because it is a USB device, it is very convenient to install, is compatible with
many operating systems, and requires no additional power source. It is a small but
important piece of a total system that allows you to economically autoguide your
telescope for long exposure astrophotography. A typical system includes your scope and
mount, a webcam with scope adapter, this interface adapter, and a personal computer
running autoguide software.
Plugs directly into your computer’s USB port.
Receives it power from your computer via the USB port, so no external power
source or battery is necessary.
Uses the USB HID (Human Interface Device) class driver, which is included
with most operating system such as Windows 98 Second Edition, Windows
2000, and Windows XP. There is no need for a proprietary driver.
Works with ST-4 compatible autoguide ports.
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Provides electrical isolation between the scope mount and the computer. This is
important to avoid noise pickup and ground loops that may be difficult to
Red-green LED for software-dependent status indication.
Is my scope mount compatible with this device?
Unfortunately, there is no universally used standard autoguider port interface. However,
many scope mount manufacturers do use a port that has become somewhat of a default
standard. This interface is characterized by a six-pin modular (RJ12) jack that has this
pinout (starting from the left as shown in this picture):
• (1) Open or sometimes powered
• (2) Common (ground)
1 2 3 4 5 6
• (3) RA+
• (4) Dec+
• (5) Dec• (6) RASome manufactures refer to this as ‘ST-4 compatible’, referring to the ST-4 autoguider
that was made by SBIG (Santa Barbara Instrument Group).
The important thing is that pin 2 is the common, and that the four direction control lines
come out on pins 3, 4, 5, and 6. The Shoestring Astronomy GPUSB adapter does not
connect anything to pin 1. Most autguide software allows the user to configure which
pin from the GPUSB RJ-12 port controls which direction of movement, so the exact
order shown above is not critical. This RJ-12 port configuration is sometimes used for
simple hand controllers as well.
Consult the manual that came with your mount to see if the autoguider port or hand
controller port uses this configuration. If this information is not in your manual, contact
the manufacturer’s technical support department.
Initial Device Installation
The first time you plug the GPUSB into a computer, it will automatically be identified as
a new device. See the section below that applies to your operating system. Operating
systems prior to Windows 98 Second Edition do not support USB and the HID class of
After the first installation is complete, the next time you plug the GPUSB into your
computer, it will remember that this device has already been installed once and will
automatically recognize it.
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To remove the GPUSB from your computer, simply unplug it from the USB port.
Installation under Windows XP or Windows 2000
Plug the device into a USB port. The red LED on the GPUSB should light immediately.
A “Found New Hardware” balloon will pop up on your monitor. Wait a few moments
and the text in the balloon should change to say “Your new hardware is installed and
ready to use”. It really is that simple!
Installation under Windows 98 Second Edition
Win98SE installation is a little more work, but still pretty simple. Plug the device into a
USB port. The red LED on the GPUSB should light immediately.
1) The “Add New Hardware Wizard” should open up. Click the “Next” button.
2) The wizard will then say “What do you want Windows to do?” Select “Search for
the best driver…”, then click the “Next” button.
3) The wizard then says “Windows will search for new drivers…”. Uncheck all the
boxes and click “Next”.
4) Next the wizard says “Windows driver file search for the device:”, and should
show the location as C:\WINDOWS\INF\HIDDEV.INF. Just click the “Next”
5) At this point, you will probably be asked to insert the Windows 98 Second
Edition CD-ROM. Do this, then click “OK”, then click “OK” again
6) Finally, click “Finish” and you should be done!
Device Operation Verification
Once you have completed the initial installation, you may want to verify that the GPUSB
is working properly before you begin to use it with your autoguide software. To do this,
you can download and install GPUSBCheck from the Shoestring Astronomy website.
This is simple software that allows you to turn the LED on and off, change the color of
the LED from red to green, and to control the directional movement of your scope mount.
It is intended to allow you to verify that everything is working properly. Should you
have trouble getting your third-party autoguide software to work, using GPUSBCheck
will also allow you to troubleshoot your setup. In other words, if everything works with
GPUSBCheck, then your problem most likely is with your third-party software.
Connecting the GPUSB to Your Mount
Connecting the GPUSB Guide Port Adapter to your mount is quite simple. Shoestring
Astronomy sells cables that are known to be compatible with this adapter. You can
make your own or buy them elsewhere, but be sure that the wires connect straight
through, i.e. pin 1 to pin 1, etc. Some cables reverse the order of the pins. Also, if you
have a simple hand controller and you want to use it and the interface adapter without
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needing to switch cables all the time, a splitter is available that allows you to plug both
in at once.
How can I be sure that my computer can control my telescope
mount through this adapter?
GPUSBCheck can be used to make sure that the adapter is actually capable of moving
your scope. Do this check right away, don’t wait until you are out in the dark trying to
take a picture to verify that your mount will respond to correction commands from the
GPUSB. First connect the GPUSB to a USB port on your computer, then run an RJ-12
cable from the GPUSB to your mount. Start GPUSBCheck and click on one of the
direction buttons. There should be movement in some direction. Remember, this
movement will be very subtle and hard to observe. The sound of the motors may be a
more obvious sign that the scope is moving. You can also try looking through the scope
at a distant object to check for movement. Click the opposite direction button and watch
for the movement to reverse. Click the button again to stop the motion. Try all four
directions to make sure they all result in movement.
If you do not see any movement, one thing to check is if your mount has a terrestrial
mode. Most mounts that do will not respond to autoguide commands if they are in
terrestrial mode.
Third-Party Software Support
The Shoestring Astronomy website shows a current list of software that is compatible
with the GPUSB. Many software applications works directly with a proprietary GPUSB
driver. Some software packages support the GPUSB by way of an ASCOM driver for the
GPUSB. Several packages allow control of the GPUSB by either of these two methods.
In order to use the GPUSB via ASCOM, you will first need to download and install the
ASCOM platform from Next, download and install the
GPUSB ASCOM driver from:
Then, follow the instructions that come with your software package for choosing and
using an ASCOM Telescope driver for autoguiding. Even though the GPUSB is not an
actual telescope, in terms of ASCOM, it behaves like a simple telescope mount that is
capable of autoguiding.
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Limited Warranty
In no event shall Shoestring Astronomy be liable for any claim for incidental or
consequential damage arising out of or in connection, manufacture, delivery or use of
any product offered on this website or by information received by US mail, E-mail,
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defects in material and workmanship for a period of one year from the date of
purchase. At its option, Shoestring Astronomy will repair or replace the defective
product. Shoestring Astronomy is not responsible for damage caused by the freight
carrier, i.e.: UPS, FED EX, etc., to our product. A claim to repair or replace the
product must be initiated by the recipient. Warranty coverage excludes normal wear
and tear, or damage caused by improper installation, any modification, abuse, misuse,
improper maintenance, and unauthorized repairs or modifications to the original
product. Warranty does not cover those parts prone to failure under normal wear and
tear. Any product repair request must be submitted and approved before shipment to
Shoestring Astronomy. Shipper is responsible for proper packaging, shipping and
insurance on approved repair items. Shoestring Astronomy will package, insure and
return ship at no cost to the customer.
Return Policy
Merchandise may be returned in new (mint) condition within 30 days of receipt for
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