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PC Control

Smart Focus
Remotely Control a Focus Motor through PC Software (Requires an Encoder Assembly)

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Smart Focus

The Smart Focus system allows one to remotely control a JMI focuser or MOTOFOCUS unit (not included) using computer software.  Popular CCD software (not included) can be used to automatically focus a CCD camera (a couple of examples are listed below).

For more information, see Purchasing Hints and Motor Control Diagrams where you can compare PCFC and Smart Focus.  Smart Focus includes a hand control, AC adapter, focuser/encoder cable, serial computer cable and basic focuser control software.  The hand unit has two directional focusing buttons, a power jack, a DB-9 serial connector and a DRO encoder jack.  It can be operated using a 9-volt alkaline battery (included).

One end of the focuser/encoder cable attaches to the hand control and the other end to the DRO encoder assembly installed on the JMI focuser or MOTOFOCUS motor (required, see below).  The serial cable connects between the hand control and the 9-pin serial port of a PC-compatible computer running Windows 95/98/NT/2000/XP/Vista/7.

Most current laptops do not include a 9-pin serial adapter.  Therefore, you will need to purchase a USB to Serial Adapter (USB to 9-pin Serial).  If you purchase a USB Null-Modem Serial Adapter you will also need a straight-through 9-pin serial cable as apposed to the 9-pin null-modem cable which we supply (please see note regarding serial ports).

JMI's standalone basic focuser control software (included on our website, call for a CD) is sufficient to control the focuser through the PC.  Automatic focusing can be accomplished through popular CCD imaging software (not included) such as Cyanogen's MaxIm DL/CCD (using SharpStar) and Software Bisque's CCDSoft (using @Focus).

Due to the modular design of the JMI EV focusers, they can be very easily upgraded after purchase to include Smart Focus.


Smart Focus requires one of the DRO Encoder Assemblies for a motorized JMI Focuser or MOTOFOCUS unit (not included).  Smart Focus includes an A/C adapter, focuser/encoder cable, serial cable and software.

Smart Focus will only work correctly with MOTOFOCUS units that can accommodate an encoder and use a non-slip coupler.  If your current MOTOFOCUS system uses a slip-clutch feature, such as an o-ring coupler, ask us about a conversion kit.  Since the Smart Focus stand-alone basic focuser control software is designed around slippage at the end of focuser travel, manual setup procedures must be used with MOTOFOCUS equipped focusers (see the Smart Focus Manual, document 29, in our Document Library).  Smart Focus is not recommended for use with an SCT focus knob due to image shift (mirror slop) and the inability to train the system normally.

Are you in need of (more) serial ports on your computer?  See how you can add more RS-232 serial (DB9 connector) ports.

An EV-2cM is shown here with the DRO encoder and hardware installed and a Smart Focus hand unit.  These components (Smart Focus hand unit, DRO encoder with mounting hardware and Focuser or MOTOFOCUS) make up the complete Smart Focus system.  The Focuser and DRO encoder and hardware must be purchased separately.
The top end of the Smart Focus Hand Unit includes a power jack, telephone-style jack for connecting to the focusing device and a DB9 (RS-232C) jack for connecting to the PC.
PC Focus Control
Remotely Control a Motor through PC Software (No Encoder Assembly Required)


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PC Focus Control for Second Motor
Remotely Control a SECOND Motor


Purchase from Farpoint*

PC Focus Control

PCFC controls a DC focuser motor from your PC through a USB port.  Basically, it replaces a regular hand unit with control from a computer using a mouse.  It gives greater control of speed and duration of movement than a regular hand unit.  It can control EV Focusers, NGF Focusers, RCF Focusers, MOTOFOCUS, MOTODEC and other motors.  No batteries are required.  There is no encoder feedback or positional display with PCFC.  If you desire focus control with encoder feedback, please see Smart Focus.  For more information, see Purchasing Hints and Motor Control Diagrams where you can compare PCFC Smart Focus.


     5-12 volt DC motor (works best with 5V motor)
     Motor cable with 1/8" (3.5mm) mono plug on the PC Focus Control end
     Windows 98 Second Edition / NT / 2000 / XP / Vista / 7 / 8 / 10
     USB version 1.1 or greater (NOTE:  Win98SE may need to be upgraded)
     Human Interface Device driver (HID) usually included with the operating system


     Control Box with integrated USB cable (3 ft length) and 1/8" (3.5mm) motor jack
          (the unit is powered by the USB port)
     Software (Free Download from JMI website)
     Operator's Manual (can also Download for Free from JMI website)

Software Console Controls:

     Pulse-width modulation (PWM) Frequency Adjustment
     Motor Speed Adjustment
     Pulse Time Interval Adjustment
     Continuous Motor Operation in Forward or Reverse
     Mouse Controlled Time Interval Motor Operation in Forward or Reverse
     Specified Pulse Time Interval Motor Operation in Forward or Reverse
     Motor Time Accumulator with Move (Return) to Zero Function
     Motor Running Indicator

* Many astrophotographers need to use two focusers, one for their imaging scope and one for their guide scope.  PCFC2 was created for this purpose.  It is identical to the PCFC hardware in all respects except for its USB identifier.  Now you can run two focusers, one from a PCFC, and one from a PCFC2.  Separate software is required (Free Download from JMI website).

NOTE The focuser cable must be purchased or supplied separately.
The PC Focus Control (PCFC) software allows one to control the pulse run time and speed of a 5-12 volt DC motor from a Windows-based computer.

Digital Readout

Encoder Assembly
For a JMI Focuser
Required for Smart Focus Product


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DRO Encoder Assembly for JMI Focuser

This is the portion of a DRO system that attaches to the JMI EV or NGF focuser.  (Specify the focuser model.)  A Smart Focus unit is also necessary for proper operation.

Due to the modular design of the JMI EV focusers, they can be very easily upgraded after purchase to include the DRO Encoder Assembly.  If you do not have a motorized version, see our EV Focuser Individual Parts for a motor upgrade.  For a visual description of the system see Motor Control Diagrams where you can compare PCFC and Smart Focus.

EV-1 / -2 / -3 / -B focusers, Part Number DROEV
NGF-XTcM / -XTnM focusers, Part Number DRONGFXT
NGF-CM / -55DM / -DX1M / -DX2M focusers, Part Number DRONGFC
Newer than 1997 NGF-S focuser, Part Number DRONGFS
NGF-1M / -2M / -3M / -4M / -55SM, older than 1998 NGF-S focusers, Part Number DRONGFO
NGF-DX3M / -DX4M / -miniCM / -miniS / -mini1M / -mini2M / -mini3M / -mini4M focusers, Part Number DRONGF

* For some NGF models, you will need to return the focuser to the factory for modifications.  Additional charges may apply for parts and/or labor.  (For more specific information, please review the notes below.)

For all JMI focusers we need to have certain information in order to supply the correct parts.  When ordering, please place a note in the shopping cart Comments area identifying the focuser.  For Event Horizon (EV) focusers, "EV" is sufficient information.  For all other focusers, specify the model and date of purchase (date of manufacture if known).

A digital picture is "worth a thousand words" in describing the specific model.  If you email a picture, please give us your Order ID along with your Name.  If we need more information, we will contact you.

This picture shows the EV-2cM focuser equipped with an Encoder Assembly.

The DRO Encoder Assembly can be retrofitted to any of our old NGF focusers.  A motor must be included with the focuser.  For an aftermarket upgrade of a manual NGF to the required motorized version, refer to Motors for JMI NGF Focusers on our Focuser Accessories page of our Online Store.

In most cases you do not need to return the focuser for the upgrade.  All NGF-1 focusers being upgraded with a motor must be returned for modifications to the base.  If you have an original NGF focuser (see DRONGFO listed above) we recommend that the focuser be returned to JMI for the motor and DRO upgrades.  With some of these original focusers we may not be able to provide the right parts without examining the focuser and there may be an extra charge for specialized parts and/or labor.  The normal labor charge for an upgrade is $20.

If you place an order without returning the old focuser, we will need to know approximately when it was manufactured.  Damage done during installation by anyone other than factory trained technicians will void the warranty.  Please see our document titled JMI Return Policy for additional information.

When upgrading EV or NGF focusers at the time of purchase, the standard hand unit is not included as this is offset by the cost of installation of the DRO Encoder Assembly.

Instructions for Installing the Encoder Assembly on an EV Focuser
The EV-2cM is shown here with the encoder and hardware installed for a DRO system.  For a Smart Focus system, the Smart Focus hand unit (left) replaces the DISCONTINUED regular DRO hand unit (right).


Encoder Assembly
Required for Smart Focus Product


Purchase from Farpoint

DRO Encoder Assemby Upgrade for JMI MOTOFOCUS

The DRO Encoder Assembly upgrades a MOTOFOCUS unit with a piggy-back DRO encoder assembly (see exceptions below).  This is the portion attached to the MOTOFOCUS motor.  A Smart Focus system is also necessary for proper operation.


The picture at left shows our DISCONINUTED DRO Hand Unit (right) along with the DRO Encoder equipped MOTOFOCUS unit.  Only Smart Focus is available now.

The piggy-backed DRO Encoder Assembly is not available for MOTOFOCUS units that use the miniature motor (e.g. Meade ETX Series, Celestron NexStar non-GPS Series, etc.  Call to see if your choice has a miniature motor.).  MOTOFOCUS units manufactured after January 1, 2000, with our standard pear-shaped motor, are upgradeable to DRO with an additional labor charge.  They must be returned to JMI for the upgrade.  Most other MOTOFOCUS units cannot be upgraded after purchase.

If you plan on using Smart Focus with a MOTOFOCUS unit, please see the notes under Smart Focus above.

When upgrading MOTOFOCUS at the time of purchase, the standard hand unit is not included as this is offset by the cost of installation of the DRO Encoder Assembly.

MOTOFOCUS with DISCONTINUED DRO Hand Unit Installed on a Takahashi FSQ-106ED with Microfocuser
DRO installed on a MOTOFOCUS motor will be somewhat different from an installation on an EV focuser.  The accuracy will vary depending mostly on how much slop there is in the focuser mechanism itself.  Note that this picture shows the DISCONTINUED DRO HAND Unit (right).
This photo shows the (MFGEN) MOTOFOCUS with DRO Encoder Assembly mounted on a Tele Vue 140 SDF using a CCD camera.  Photo and comments provided by Dan Richey.


What is Smart Focus?

Smart Focus is a combination of hardware and software for precise remote control of JMI's motorized focusers through a personal computer's serial port.  The system can be controlled three ways:  1) manually using the control box, 2) with the included basic focuser control software or 3) through third-party auto-focus functions found in popular CCD imaging software such as Software Bisque's CCDSoft and Cyanogen's MaxIm DL/CCD.  Auto-focus software automatically brings the system into focus using the CCD camera in conjunction with Smart Focus.  (JMI's focuser control software does not include an auto-focusing function.)

The system includes a hand control box (AC or DC power) and PC compatible focus control software.  The hand control includes a jack and cable for connecting to the focuser and a 9-pin serial RS-232 connector and cable for software control using a personal computer.  (See the diagram below.)

What is PC Focus Control?

PC Focus Control (PCFC) replaces your focuser hand unit with precise motor control from the USB port of a Personal Computer (PC).  You can use the free downloadable JMI Windows-based software or any ASCOM-compatible software.  Our testing shows that PCFC gives much greater control than a normal hand unit and we were able to get 0.0004" drawtube movement.  There is no encoder feedback or positional display with PCFC.  If you desire PC focus control with encoder feedback, please see Smart Focus.  (See the diagram below.)

What is a Digital Readout (DRO)?

Digital devices such as our DRO Encoder Assemblies give precise discreet signals indicating increments of movement.  This movement is usually a shaft in the encoder that is connected to moving parts of a telescope or accessory, such as a focuser, by gears, belts or a friction drive.  This digital data is fed to a device that shows, in a digital format, the movement of the focuser.

Our original electronic Digital Readout (DRO) system provided precise information on focuser position with an easy to read LED display.   The four-digit display and focus control were integrated into one DRO Hand Unit.  That unit was discontinued but we still have the Smart Focus system which interfaces to a Microsoft Windows based Personal Computer.  With unprecedented focusing accuracy, you can return to any previous focus position after swapping equipment or users.  This is especially helpful when returning a CCD camera to focus after visual verification of the position of your telescope.  (See the diagram below.)

Purchasing Hints

Here are a few Typical Configurations for digital focusing on a Schmidt-Cassegrain Telescope (SCT).  They include part numbers and basic specs for comparison.

Smart Focus PC Control with an EV-1 on an SCT
EV1CM   EV-1 Event Horizon Focuser designed for Cassegrain Telescopes with Motor included (Model EV-1cM)
DROEV   Encoder and Mounting Hardware for EV focusers
SFDRO   Smart Focus Hand Unit, Cable and Basic Software

   Requires a computer with a Microsoft Windows based operating system
   Basic control software is included (Other popular CCD imaging software can interface with Smart Focus)
   Can be controlled by the computer or hand unit (included)
   Encoder feedback gives accurate positioning
   Greatest amount of control, accuracy and repeatability ( 0.001")

PC Focus Control (PCFC) with an EV-2 on an SCT
EV2CM   EV-2 Event Horizon Focuser designed for Cassegrain Telescopes with Motor included (Model EV-2cM)
PCFC   PC Focus Control and Basic Software

   Requires a computer and Microsoft Windows based operating system software
   Controlled by computer software (included)
   No encoder feedback (more susceptible to environmental conditions)
   Great amount of control and accuracy

The following is a Visual Summary of the products found on this page along with the standard single- and dual-control hand unit configurations for comparison.





Click on parts of the pictures above to link to related products, pictures or descriptions.

Customer Comments

NOTE:  Customer comments may include comments about our DISCONTINUED DRO Hand Unit.

"Thank you so much for your personal attention to my problem.  I am very impressed.  I was able to resolve the problem with your phone support....  I am now a happy observer enjoying my Smart Focus and will not need a replacement."  (W. D.)

"...thanks for such a well-made product!  Everything about it shows the commitment and quality your company puts into their products.  I'm looking forward to years of seeing and imaging with [Smart Focus]!"  (J. C.)

"I am very impressed with the overall quality and machining of the NGF-CM.  The DRO motor and hand unit are very well made.  The digital readout is terrific.  The weight of the hand unit seemed a bit heavy for its size, at first.  Once I got used to it, I actually enjoyed it.  I consider the NGF-CM/DRO combo one of the best purchases I have made for my trusty Celestron C8.  I also like the C8 OTA carrying case a lot.  It is much nicer than lugging my OTA around in a big foot locker not to mention much lighter and less awkward.  Thank you for your great products.  (B. D.)

"I just wanted to say thanks for all your help in getting my Smart Focus/DRO running.  I downloaded the drivers with the COM 5 variation and it worked just perfect.  I did not have a 9-pin serial port so the IOGEAR USB adapter worked just as you suggested."  (J. P.)

"This is a short note of satisfaction.  I received my upgrade to Smart Focus last week to be installed on my NGF-S focuser.  I was positively impressed by the quality and the simplicity of the product.  It took only a few minutes to install and the touch and feel is of a high quality product.  I have used it a few times and it is very accurate.  I also used it with the Cyanogen MaxIm DL control software using autofocus and it worked like a charm.  Just wanted to give you feedback.  You have a great product."  (R. L.)

"I have an NGF-S with DRO.   It is a real pleasure to use and it works flawlessly.  It's another credit to your fine craftsmanship....  I absolutely love (it).  It's a real gem and has made accurate focusing easy to achieve."  (L. D.)

"...The [MOTOFOCUS with DRO] runs smoothly and accurately.  Thanks for your good workmanship and excellent service."  (D. R.)

"It is nice to deal with a company that is sincerely committed to offering a top-quality product and backing it up with customer service to match.  Needless to say, whenever I need an accessory for my scope, I'll call JMI."  (J. E. G.)

Frequently Asked Questions (FAQ)

Q. I get the following error message when attempting to run the PCFC software:
Component 'MSCOMCTL.OCX' or one of its dependencies not correctly registered:  a file is missing or invalid
What is the problem?
A. You can find the answer at

The relevant contents of that page are reproduced here:

Sometimes certain Microsoft Libraries can become unregistered when installing and uninstalling a lot of software.  One very common problem is the MSCOMCTL.OCX.  To correct the error, first search your drive for MSCOMCTL.OCX to see if you have it.  If not, you can download it from HERE.  The file should be placed in your C:\WINDOWS\SYSTEM directory or C:\WINDOWS\SYSTEM32 if you are using WinXP.  Once it is there click START > RUN and type "REGSVR32 MSCOMCTL.OCX" (No quotes) in the box.  That should fix the problem.

You can also download the above mentioned file here from our website.

Q. I do not have enough serial ports to use Smart Focus with the telescope control software I am using.  What can I do?
A. See some options for adding serial ports through a USB port or PCMCIA slot.
Q. I would like to control the system from a distance.  How long can the control cable be?
A. We have sold many cables with lengths of up to 150 feet without any problems.  Anything longer may work but will not be guaranteed to operate properly.
Q. My computer places Smart Focus on a COM Port numbered higher than the maximum of 5 allowed by Smart Focus.  What can I do?
A. Check for forced COM port addresses and/or IRQs in the Windows Device Manager or in the BIOS settings.  If this is the case, determine the reason that these items have been configured manually.  If you allow the computer to use automatic settings, it should alleviate any problems.  If not, try forcing Smart Focus to a lower COM Port via the Device Manager or BIOS and reboot, allowing all other devices to be assigned a port and IRQ automatically.  You should be able to accomplish this by manually applying or forcing a particular address/IRQ combination to the serial port (or USB port if using a USB to Serial adapter).
Q. Is there a discount when purchasing a "C" series focuser (EV-1c, EV-2c, EV-3c, EV-Bc) with Smart Focus since the Smart Focus hand unit replaces the regular hand unit?
A. No, the reduction one might otherwise receive due to the removal of the regular hand unit is offset by the cost of installing the DRO Encoder System on the focuser.