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MC3 Mk II Motor Controller for Telescope Mounts with UMi Pro Planetarium and Telescope Control Software

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Ursa Minor MC3 Mark II Universal Stepper Motor Controller for Telescope Mounts

(MC3 is compatible with the Meade LX200 protocol. This makes it compatible with most commercial or free telescope control software available today.)

Ursa Minor Pro Planetarium and Telescope Control Software included

Ursa Minor's MC3 is an universal stepper motor controller for medium to large telescope mounts. Although designed specifically for astronomical telescope mounts, but it is more universal: it can be used to control panoramic photo heads and custom made timelapse devices as well.
This new version is also compatible with its own hand controller that is recommended.  The Skywatcher GOTO handset was always an easy way to control the MC3 motor controllers, however, due to the difficulties with the constant changes to the Skywatcher firmware, the manufacturer decided to develop their own handset with better functionality that the Skywatcher handset was ever providing. This also means that the Skywatcher handsets will be not supported in the future, although the MC3 is still compatible with it up to firmware version v. 3.0.


  • MC3 telescope motor controller unit
  • AC-DC PSU (mains adapter) with connector cable to connect to the above MC3 unit (input: 100-240VAC, 50/60Hz, 1.4A, output: 24V, 2.5A)
  • Mains adapter cable for the above PSU (We can supply UK or European type cable, but not other country standards. You'll have to source it locally. You'd need a cable with a kettle-type connector on one end (IEC 60320 C13) and a mains adapter on the other end.)
  • USB cable

Above image shows a PSU cable that you'll have to source locally if you'll use the MC3 controller in the USA as at the moment we can only supply the UK and European type cables for the PSU.

Please note, on the main picture: SynScan hand control unit, electric motors and interface cable are not included, for demonstration only.

The device can be used with varios kinds of bipolar stepper motors. Some examples shown below:


Please note, above motors are not included, just for demonstration.



  • Supporting two stepper motors: 2 phase, max. 2.5A per winding.
  • Resolution: Full step to 64 x microstep (automatic)
  • Smooth running, acceleration, deceleration.
  • Precise positioning (goto)
  • Totally parallel operation: Running two motors, transmit and receive data through the serial interfaces at the same time.
  • Flexible configuration: current limit, resolution, acceleration parameters, deceleration parameters, speed limit values can be configured independently for the motors.
  • Freeware Windows based program for testing and configuration.
  • Three protocols: Ursa Minor native, emulated Synta Skywatcher EQ5 protocol, basic Meade commands (only for autoguiding).
  • Compatible with Synscan hand control
  • Supported by Ursa Minor Pro program (native) and with most of the popular astro softwares through the freeware EQMOD Ascom driver.



This device is suitable for medium to large telescope mounts. It provides control, goto (automatic positioning to the selected celestial object), auto-guiding (Tracking the selected object) functions. The equipment drives two-phase stepping motors.

Supported mounts

The MC3 can fit to multiple telescope mounts. It depends on two things: the type of motors used and the gear ratio. The MC3 can drive two phase bipolar stepper motors and can be configured to wide range of gear ratios.

The operation is guaranteed (tested) with these mounts:

Fornax 51, 100, 150 mounts

These are popular Hungarian-made mounts. Robust, rugged, heavy duty, accurate equipment. The MC3 is compatible with all family members of the Fornax 51, 100, 150 family. You can buy the MC3 control together with the mount. In such case you can ask us to make all the complete configuration, set-up work and your system will be ready to use immediately.

Stabi mounts

These precise mounts are also Hungarian-made. They are a bit smaller and more transportable than the Fornax series. You can buy the MC3 control together with the mount. In such case the complete configuration, set-up work is carried out by us. Your new mount will be immediately ready to use.

Gemini G42 and F53

The standard motor control for Gemini mounts is the Gemini Pulsar. The MC3 gives you a cost effective alternative. They are able to control the Gemini G42 mount. The F53 model is also supported but without the encoders.

Skywatcher EQ6 and EQ8

These Skywatcher mounts has a built-in electronics and fast stepper motors. After removing the original electronics and provide direct connections to the motors, the mount will be ready to work with MC3. It has more advantages: The Ursa Minor Hand control has many improvement: (battery backed real time clock, easy operation with one hand, easy selection of reference star by choosing it on a displayed chart.) Thanks to the advanced electronics of MC3, the motors will run more smooth and they will be capable for higher speed.

Use with hand-held controller or computer

For using the MC3 you will need a hand control or a computer (with appropriate software). The following list summarizes the options:

Ursa Minor hand control

Easy to use hand control, developed directly for the MC3. For more information, please go to this page.

Connection with Ursa Minor Pro program

The Ursa Minor Pro program directly supports the MC3 controller, ASCOM driver is not required. Using fewer software components and additional drivers gives more convenient way to use. The Ursa Minor Pro gives some extra functions: DSLR camera control, sequential shooting, sending autoguider and goto signals in one cable.

Using MC3 with other programs

The MC3 controller is compatible with EQASCOM driver. Any program that supports the ASCOM standard, capable of controlling the MC3. Note: The ASCOM software is not an Ursa Minor product, for support and information you may visit the www.ascom-standards.org homepage.

Technical Specifications

Features and Electrical parameters

DC supply voltage 12V - 30V (24-30V stabilized power supply recommended)
Max. supply current 2,5A
Max. motor pulse current 1,8A
Minor Hand Control Ursa Minor Hand Control
USB port +
Autoguider port RJ/11 (6 pin telephone socket) ST4 compatible
DSLR output 2.5mm stereo jack, opto-isolated

The device can be used with various kind of bipolar stepper motors. Some examples shown below:

Stepper motors

Front connections

Connection on the front panel of the MC3 telescope controller

MC3 front connections from left to right: Autoguider, Ursa Minor hand control, Utility connector (For Bluetooth interface or other accessories) USB port, DSLR camera remote output.

Rear connections

Here you can find the power supply connector, the on/off switch and connectors for two motors:

Rear connectors

Pinout of the power supply connector:

MC3 power connector pinout

Wiring the motor connectors on the back side of the MC3. Each wire has two pins tied together providing more reliable connection.

Stepper motor connection (DB9 socket pinout)

Fornax mounts have 4 pole circular motor connectors. The following image shows the construction of the necessary motor cable. One cable required per motor.

Motor cable for MC3 and Fornax mounts

Gemini G42 mounts have one 15 pole D-Sub connector as motor connector. Both of the two Motors are wired to it inside of the mount. The following image shows the construction of the necessary motor cable to connect the G42 to the MC3.

Gemini G42 mount Adapter cable for using MC3 with Gemini G42 mount

Compatibility with telescope mounts

The device was developed originally to control different types of telescope mounts. It can be ordered preprogrammed for these mounts:

  • Fornax 51, Fornax 100, Fornax 150 (Old and new models (Different gearing))
  • Stabi-7
  • Gemini G42

Illustrations: Left:The Motor Controller connected to Gemini G42 mount. Right: Using MC3 with Fornax 50 mount.

MC3 motor controller with Gemini G42 MC3 motor controller with Fornax 50 mount

Important thing: The east / west position of the mount

There is an important issue when you are using a german equatorial mount: The sky cannot be scanned with the telescope from the eastern horizon to the western horizon. Somewhere at the middle the telescope may collide to the mount. In such case you should do a Meridian-flip: Move the tube to the opposite side of the mount.

Please imagine you have a german equatorial mount. The telescope is pointed to the South towards a star near the equator. In such case your telescope may in one of the two possible positions:

Eastern position:

The telescope is at the eastern side of the mount. The counterweight shaft is pointing to the West.

Western position:

The telesope is at the western side of the mount. The counterweight shaft is pointing to the East.

It is essential to know which position you are using. Not only you, the Motor driver unit also must know this. It is essential because the rotation direction of the declination motor is the opposite in the two cases.

The motor control unit does not know it as its own. You should tell it.

There are buttons in the mcconfig program and menu options in the Ursa Minor Pro program for such purpose. You can read more about this later in the documentation.

What to do before use


Connect the cables only when the power is off!

  • Connect the motor-cables of the mount to the two-D9 connectors at the back of the MC3 controller.
  • Connect the power supply unit to the MC3-controller (PSU is already plugged in into the mains socket), but do not yet turn on the device.
  • Connect either the Ursa Minor hand control unit or a computer (but only one at a time, never both at the same time as that will confuse the electronics as the MC3 would want to process information from two competing sources).

When you use it first time for the initial settings you would need to connect it to a PC or laptop.

Connection to the computer via a USB port

  • Download and install the FTDI USB serial driver.
  • Connect the MC3 to the computer via a USB cable if you have not already done so.
  • Turn on the MC3.
  • Find out what is the COM port number of the device.
  • Start the program ”mcconfig” for the initial setup.

Initial setup using computer

The MC3 device normally comes pre-configured for the Fornax mounts. (Exception: if you buy with a different mount and also ask us to pre-configure it.) You may need to adjust settings for your equipment even if you already have a Fornax mount.

A program called “mcconfig” serves to setup the mount.

You can download it from here:

  • MCConfig version 2.3, for the current versions of MC3: mcconfig_2_3.zip
  • The same version of the program, but the filename does not include the version number. This link always will point to the up to date version in the future: mcconfig.zip

The program requires no installation. Just unzip the zip file. The program's user interface looks like this:

MCConfig: Setup program for configurating MC3. Setting the gear ratio in MCConfig.

Steps of initial configuration

Before doing anything, consider the east-west position of the mount. We recommend the following initial position:

The scope is at the eastern side of the mount and looks to the equator. The counterweight shaft is horizontal and points to the West.

Recommended starting position when use MC3

The mcconfig program assumes this initial position.

  1. Connect the MC3-controller to your computer, if you have not already done so. (via a USB cable)
  2. Turn on the MC3-controller and start the program “mcconfig”.
  3. Select the COM port number (that you found out after the installation of the FTDI driver) from the drop-down list in the upper left corner of the window. The COM number can be discovered by this way.
  4. Press the Connect button and wait until the connection is established. Below the Connect button the following message would be displayed "Connected".
  5. Once connected, the program reads the settings from the MC3 and accordingly resets all the controls in the window.
  6. If you are using older MC3: Check it out if your mount has been correctly selected! You would be able to choose only form mount-dependent pre-set rate values as the old MC3 cannot work in arbitrary gear/rate ranges. For new MC3 models: You should check de gear ratio and modify it if required.
  7. With the help of the four direction buttons at the top left corner of the window you can now try to move the motors. When you click the arrow button the mount would start to move in that direction. To stop it you would have to click on the STOP button that is placed in between the four direction buttons. Until you click on the STOP button, the motors will NOT stop moving!
  8. Under the text field under the "Select mount type" field you will find the full list of supported mounts and gears. Make sure that your mount is selected or if not then select the right mount. When you choose a different mount, all the default settings will be automatically modified according to the chosen mount.
  9. Make sure that the RA axis of your mount is connected to the right port and that it tracks in the direction of East to West. First, stop the motor (if you have not done yet), then press the button “Track On”. Tracking starts.
  10. Check out if it tracks in the right direction and whether the object remains in the telescope's field of view.
  11. If the motor rotates in the opposite direction then thick the “Reverse Rotation” checkbox under the RA panel.
  12. Proceed likewise if the declination motor has been wired in reverse, too.
  13. If you have completed all the above necessary steps/settings, there is one important step remains: You have to store the settings in the memory of MC3. To do this, press the “Write to EEPROM” button. When you turn the MC3 on next time, it’ll work with the new settings.
  14. If you have finished with setting it up, disconnect it by clicking on the “Disconnect” button and then turn off the MC3.

Recommended MC3 configuration parameters for some popular mounts

  Fornax 52 standard Fornax52 "Photo" Fornax152 "Photo" Stabi 1.0
Gear ratio 172800 829440 829440 179500
Motor steps 200 400 400 200
Idle current 600 mA (*) 600 mA (*) 600 mA (*) 400 mA (*)
Tracking current 1400 mA 1600 mA 1600 mA 1000 mA
Running current 1400 mA 1600 mA 1600 mA 1200 mA
Max. speed (30V) 400 x 300 x 260 x 540 x
Max. speed (24V) 360 x 260 x 220 x 540 x

(*): Remark: For optimal guiding performance, the idle current for DE axis should be set to the same value as the tracking current.

Remark 2.: The Fornax "Photo" mounts have very high gear ratio. (4.8 times larger than standard Fornax mounts) This makes difficult to provide high speed movements. The step frequency needed to 300 x speed may produce 1440 x speed on a standard Fornax mount. This high speed is not recommended in most of the cases.

Initial configuration with Ursa Minor Handbox

English text coming soon...

Upgrade the internal firmware of the MC3

You can upload new firmware into your existing MC3. New firmwares are released when new development or bug fixes were made. Use the MC3_bootloader program for that purpose:

Firmware uploader az MC3-hoz

You also need a firmware file. These can be downloaded form there.

The upgrade procedure consists of four steps, as the user interface of the program also separated into four areas. Each area in the window has a title. The title of the active area is displayed with bold fonts.

The steps of the upgrade process:

  • Connect the MC3 to the computer and switch it on.
  • Do the step one in the Uploader program: Open the firmware file. After the file opened, the program validates it. When the file is correct, the program let you step tot the second phase.
  • Connect to the MC3. Choose the COM port number, and press the Connect button. The program will check the version of the MC3 hardware and checks the compatibility with the new firmware file. If the file is compatible with the MC3, the program let you step to the third phase.
  • In this phase you can start the uploading process. This may take a few minutes. The progress is displayed in the status field. (Number of total sectors and number of uploaded sectors.)
  • When the uploading is done, you should close the program and switch off the MC3.

Important: After uploading a new firmware, the MC3 should be restarted before use it.

Important: Upgrading the firmware will reset the MC3 parameters. You should configure it with the MCConfig again.

Upload the firmware in Safe Mode

When an error occurs during the firmware upload, the MC3 may not start properly on the next startup. In such case the uploading a new firmware also may not be possible.

When this situation happens, you should start the MC3 in safe mode:

  • Open the MC3: Remove the cover of the device.
  • Locate the jumper. There is only one jumper inside the MC3.
  • The jumper is in the open state normally. Put it into the closed state.
  • Start the MC3. The two autoguider LEDs will blink alternatively. It indicates, that he MC3 is in programming mode.
  • Upload the firmware as normally.
  • When the upload finished, switch off the MC3 and put the jumper back into open state.

Important: Open the MC3 only when the power is off! Handle the jumper only when the power is off!

Using MC3 with the Ursa Minor Pro program, without any hand control

In the case of fixed installation of a telescope inside a dome we do not always need a hand-held controller. All functions can be used/accessed from the user interface of the Ursa Minor Pro.

If you want a hand-held remote controller, you can use simple USB Controllers. See the following page. (under construction)

Using with Ursa Minor hand controller

The Ursa Minor hand controller is designed directly for MC3. You can read abot it on separate page.

Ursa Minor hand control

More information »»

Auto Guiding (Automatic Tracking) with a computer

In this example you can read about how the MC3 works together with an autoguider program running on your computer. There are many different ways of guiding with a computer, but in this example we will be using the GuideMaster program.

In this example, we do not use a planetarium program. The GOTO positioning will be carried out by using a hand controller unit. The guiding is done by a help of a webcam and the free Master Guide program.

The steps are as follows:

  • Connect the hand controller to the MC3.
  • Connect the MC3 to your PC with a USB cable. The MC3 autoguider port is left blank.
  • Turn on the MC3.
  • Find out what COM port number was allocated to the MC3.
  • Start the GuideMaster program.

Goto and Auto Guiding with the Ursa Minor Pro and GuideMaster programs

The Ursa Minor Pro will get your telescope into position of your object as well as it provides manual positioning, while guiding (automatic tracking) will be achieved by the GuideMaster program. The MC3 is connected to the computer with only one USB cable. Signals for telescope control as well as for guiding being sent through this cable alone.

To be continued...


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1 Most recent customer reviews (see all reviews):
joe perry
Mar 19, 2016
This customer purchased the item at our site.
I am running two of the mc3 boxes. I used one on a home built pipe mount with Byers expensive RA and DEC gears. Interface to the mc3 is easy to use. I use the synscan handbox controller and not the mc3 handbox. i have not tried the mc3 handbox.

Advantages: You can use almost any type of stepper motor. But, if the stepper rotates too fast then the GEAR RATIO has to be large. If the stepper rotates too slow it might stall. Watch the wiring for the 4 and 6 wire steppers. Both will work if wired correctly. You can get the GPS syncscan adapter from Canada Company. That lets it set the lat/long and time.

Disadvantages: Warning, if you use the synscan hbx, it must have version 2.27 or 2.28. Any other code will not work. Do not buy the synscan 3.x or upgrade the one you might purchase. You can not downgrade from 3.x to 2.27. I tried that and it did not work with the mc3. I have had to play with the GEAR ratio the MC3 uses. You have to do some star tracking and determine the too fast or too slow error and adjust the Gear Ratio number in the MC3.

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