Celestron 94155 Instruction Manual

FOCU S MOTOR FOR SC T & EDG EHD INSTRUCTION MANUAL

FOCUS MOTOR
FOR SCT & EDGEHD

INSTRUCTION MANUAL

ENGLISH • MODEL #94155

The Focus Motor for SCT & EdgeHD provides
hands-free focusing for Celestron Schmidt­Cassegrain telescope (SCT) and EdgeHD telescope
optical tubes. This is a great convenience, especially
for astroimagers with remote telescope setups and
people who have dexterity issues that limit their ability
to use a focus knob.

The focus motor is compatible with all Celestron
SCTs from 6” to 14” in aperture that have
been produced since the year 2006; it is not
compatible with 5” SCTs or older models. It is
compatible with all EdgeHD optical tubes, the 8” and
36cm Rowe-Ackermann Schmidt Astrograph (RASA)
models, and the Celestron 7” Maksutov-Cassegrain.
The focus motor can also be used with the 11” RASA,
but requires the Focuser Retrofit Kit for the RASA 11
(#94255).

CHECKING CLEARANCES

The focus motor protrudes outward from the rear cell
of the telescope. After installation, check to make
sure the focus motor does not interfere with the
telescope’s mount as it points to different parts of
the sky. Specifically, if using a fork mount that has
adjustable positioning of the optical tube on the fork,
such as the NexStar SE and NexStar Evolution mounts,
make sure the focus motor does not interfere with
the mount when pointed straight up (or at the pole if
using an equatorial wedge).

If using a Celestron computerized mount, the focus
motor can be powered by the mount, and allows
focus control from the telescope’s hand control
or from a computer connected to the mount. If not
using a Celestron mount, the focus motor can be
controlled directly by a computer via a USB cable,
and is powered by the USB connection or an optional
12V DC power supply.

Please read through the entire instruction manual
before attempting to use the focus motor. The
manual will guide you through the various methods
of powering and controlling the focus motor. For
installation instructions, refer to the Setup Guide
included with the focus motor.

If it does interfere, simply reposition the telescope on
the fork mount until the focus motor clears the base.
The telescope may be a bit out of balance, but it should
not affect performance.

To prevent interferences, the focus motor orientation
relative to the telescope’s rear cell can also be changed.
This is done by using a different set of mounting holes
to mount the focus motor onto the focuser cover plate,
or by rotating the cover plate itself. Refer to the Setup
Guide for more information.

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FOCU S MOTOR FOR SC T & EDG EHD INSTRUCTION MANUAL

USING THE FOCUSER MOTOR
THROUGH A CELESTRON COMPUTERIZED MOUNT

METHOD 1: WITH THE NEXSTAR+
OR STARSENSE HAND CONTROL

If using a Celestron computerized mount, the focus
motor can be powered and controlled from the
mount. This is done by connecting the AUX port on
the focus motor to an AUX port on the mount using
the supplied cable. If there are no available AUX
ports, the optional Celestron Aux Port Splitter can
be purchased.

Once connected to the mount’s AUX port, the focus
motor can be controlled from the mount’s hand
control. Both the the NexStar+ hand control (requires
version 5.30+ of the fi rmware) and the StarSense
hand control (requires version 1.19+ of the fi rmware)
are compatible.

NOTE: If your hand control fi rmware is not up-to-date, use the

Celestron Firmware Manager (CFM) to update it. This
program can be found at celestron.com/CFM.

The focus control can be accessed by pressing the hand
control’s MENU button, then selecting “Focuser.”

METHOD 2: WITH A COMPUTER

When connected to the AUX port, the focus motor
can also be controlled through the mount from a
computer. This is especially desirable when doing
astronomical imaging, as this will allow control of both
the mount and the focus motor from the computer.
Connect the hand control to the computer using a
USB A-to-mini B cable (not included). One end of
the cable is connected to the USB mini B port on the
bottom of the hand control, the other end is connected
to the computer.

Once connected, you can use most any astronomy
telescope control software that has focuser
control by using the Celestron Unifi ed ASCOM
mount driver, which can be downloaded from
ascom-standards.org.

The focus motor controlled by the NexStar+ hand control through a
Celestron mount.

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The focus motor controlled by a computer through a Celestron mount.

FOCU S MOTOR FOR SC T & EDG EHD INSTRUCTION MANUAL

Celestron also offers FREE Windows PC software
that directly controls the focus motor without
the need for an ASCOM driver. The simple
Celestron Focuser Utility Program application
can be downloaded from the Focus Motor
product page at celestron.com/FocusMotor.
Alternatively, the focus motor can be controlled
with the Celestron PWI software. This program
is available at celestron.com/CPWI. If using either of
these two programs along with the Celestron CGX
or CGX-L mounts, the computer can be directly
connected to the mount’s USB port (requires a USB
A-to-B cable).

NOTE: If control commands arrive from multiple sources,

such as the hand control and a computer program,
the focus motor will answer all commands in the order
they arrive.

The free Celestron Focus Utility Program provides a simple

user interface for controlling the focus motor.

USING THE FOCUS MOTOR
WITHOUT A CELESTRON MOUNT

If you are not using a Celestron mount, the focus
motor can be powered and controlled via the USB
port. This can be done by connecting it to a USB3
port or a USB2 port that provides at least 900 mA. To
connect to a USB port, you will need a USB A-to-B
cable (not included). Make sure to use a good quality
cable, or the motor may not receive enough power.
Connect the cable to the USB port on the focus
motor, and connect the other end to your computer
or USB hub.

Alternatively, the focus motor can be powered from
a 12V DC power source. The power source needs
to be able to supply at least 1A. Connect the power
source to the 12V DC jack on the focus motor using
a tip positive 5.5mm/2.1mm cable. Using an external
12V DC power source will prevent your laptop battery
from being drained by the focus motor. Also, if your
computer’s USB2 port does not provide enough
power, an external 12V DC power source can
be used.

To use the focus motor with astronomy software,
you will need the Celestron USB Focuser ASCOM
driver, which can be downloaded from the Focus
Motor product page at celestron.com/FocusMotor.
Celestron also offers FREE Windows PC software
that directly controls the focus motor without the need
for an ASCOM driver. The simple Celestron Focuser
Utility Program is available on the Focus Motor product
page at celestron.com/FocusMotor.

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The focus motor controlled directly from
computer through its USB port.

FOCU S MOTOR FOR SC T & EDG EHD INSTRUCTION MANUAL

CALIBRATING THE FOCUS MOTOR

Before using it for the first time, we recommend
calibrating the focus motor to indicate where the
inward and outward limits of mechanical focuser travel
for the telescope are. This will prevent the motor from
reaching the focuser limits and straining the motor.
Calibrating the focuser also sets the focuser index
positions so that accurate “Move To” commands
can be executed. The focus motor only needs to be
calibrated during the initial setup or if it is removed
and reinstalled on the optical tube. After calibration,
the focuser limits and index positions are stored in the
focus motor.

To calibrate using a Celestron hand control, press the
MENU button, then select “Focuser,” then “Calibration.”
If using either the Celestron Focuser Utility Program
or Celestron PWI software, calibration can be done
directly from the program’s user interface.

If using an ASCOM driver along with third-party
focuser control software, you can calibrate with
the driver. Select “ASCOM focuser” as the focuser,
then for Focuser Settings select “Celestron USB
Focuser.” The calibration routine can then be accessed
from the “Properties” button within the ASCOM
Focuser Chooser.

The focus motor can be calibrated using any of the above
methods and will not need to be done again if changing
how the focus motor is controlled. For example, you can
calibrate with a Celestron hand control and then use
third-party software without needing to calibrate again.

When initiated, the calibration routine will slew to
the inward focuser travel limit, then to the outward
travel limit. This process takes several minutes. When
completed, the full range of travel will be indexed
from zero (the inward limit) to 1000x the number of turns
of the focuser knob needed to reach the outward limit.
So, for example, if the focuser knob has a total of 40
turns of travel, the focuser positions will be indexed from
0 to 40,000.

USING THE FOCUS MOTOR

There are two ways to control the focus motor: the
motor can be manually slewed to change focus or
it can automatically slew to a specific focuser index
position.

If using a Celestron hand control, you can manually
slew the focuser by pressing the MENU button, then
selecting “Focuser”, then “Move In/Out”. You will then
be prompted to select a motor speed rate, from 1
(slowest) to 3 (fastest). The rates correspond to the
following knob rotation rates:

RATE 1: 8°/sec

RATE 2: 32°/sec

RATE 3: 128°/sec

Then, use the SCROLL DOWN and SCROLL UP
buttons to rotate the focus knob. Specifically, the
SCROLL DOWN button will rotate the focus knob
clockwise, which moves the primary mirror inwards (i.e.
towards the rear cell), and the SCROLL UP button will
rotate the focus knob counter-clockwise, which moves
the primary mirror outwards (i.e. towards the Schmidt
corrector).

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FOCU S MOTOR FOR SC T & EDG EHD INSTRUCTION MANUAL

If you wish to change the motor speed rate, simply press
the BACK button, and select another rate.

If using with the Celestron Focuser Utility Program or
Celestron PWI, you can manually slew the focuser by
using the MOVE IN (rotates the motor clockwise) and
MOVE OUT (rotates the motor counter-clockwise)
buttons from the user interface. Change the speed rate
by using the Rate slider.

When the focus motor is in use, you can see the rear of
the motor’s clamping collar rotating. There is a reference
printed in white on the focus motor to determine which
way the primary mirror is moving within the telescope.
The reference indicates that when the motor is rotating
clockwise, the primary mirror is moving in the negative
direction (i.e. towards the rear cell), and when the motor
is rotating counter-clockwise, the primary mirror is
moving in the positive direction (i.e. towards the Schmidt
corrector).

You can go to a specific focuser index position by using
a “Move To” command. If using a Celestron hand control,
press MENU and select “Focuser”, then “Move To.” From
here, you can enter a focuser index position and the
motor will automatically slew to that position. When using
the Celestron Focuser Utility Program or Celestron PWI,
enter a focuser index position in the MOVE TO window,
and the motor will automatically slew to that position.

The “Move To” function is convenient to use after you
have determined the best focus for your setup. Take note
of the focuser index position, and you can automatically
return to that position in the future. The current index
position is shown on the “Move To” screen for the
hand control, and above the MOVE TO button for the
Celestron Focuser Utility Program and Celestron PWI.

NOTE: When using the “Move To” command to automatically

move the focuser to an index position, the focus motor will
always approach focus in the positive direction (i.e. with
the focus knob rotating counter-clockwise and the primary
mirror moving outward). This is done to ensure the best
accuracy of the “Move To” command, as it eliminates any
potentially “lost” index position steps due to backlash in the
telescope’s focuser system. If the desired index position is
inward (i.e. a lower number) from the initial position, the
focus motor will move 500 steps inward past the selected
index position before reversing direction and returning to
the selected position.

The “+” and “-” reference printed in white on the motor indicates the
direction in which the primary mirror is moving.

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FOCU S MOTOR FOR SC T & EDG EHD INSTRUCTION MANUAL

BACKLASH SETTINGS

When changing direction of the focus motor, you may
notice a little bit of backlash in the telescope’s focus. This
means that the motor is turning a bit before the focus of
the telescope changes. This will typically manifest itself
when critically focusing on a star using the slowest motor
speed rate. You can compensate for this backlash with
the backlash setting.

In the Celestron hand control, the backlash setting can
be found by pressing the MENU button, then selecting
“Focuser,” then “Backlash.” For the Celestron Focuser
Utility Program or Celestron PWI, there is a Backlash
Settings slider in the user interface. The backlash setting
can be set from 0-99.

To fi nd the best backlash setting, fi rst acquire a bright
star in your telescope’s fi eld of view and roughly focus it.
Next, set the motor speed rate to its slowest setting and
defocus the star using one of the hand control’s SCROLL
buttons, or the MOVE IN or MOVE OUT command from
the computer program. Defocus the star until you can

PORT COVERS

clearly see the out-of-focus “doughnut” star image. Now,
reverse direction of the focus motor. If the defocused
star image immediately starts becoming smaller, then
the backlash setting should remain at 0 (i.e. the default
setting). If you notice a bit of time elapsing before the
image begins changing, then increase the backlash
setting. Repeat this procedure until the focus of the
telescope immediately changes when changing direction
of the focus motor. If you set the backlash setting too
high, you will notice the focus rapidly changing as soon
as you change directions, and it may “overshoot” your
desired focus. If this occurs, decrease the backlash
setting.

To best protect the focus motor, keep the tethered covers
on the ports when not in use. When the ports are in use,
the covers can be hooked onto the posts on the side of
the focus motor to keep them from dangling.

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FOCU S MOTOR FOR SC T & EDG EHD INSTRUCTION MANUAL

CELESTRON TWO YEAR LIMITED WARRANTY

A. Celestron warrants your telescope to be free from defects in materials and workmanship for two years. Celestron will repair or replace

such product or part thereof which, upon inspection by Celestron, is found to be defective in materials or workmanship. As a condition to
the obligation of Celestron to repair or replace such product, the product must be returned to Celestron together with proof-of-purchase
satisfactory to Celestron.

B. The Proper Return Authorization Number must be obtained from Celestron in advance of return. Please submit your request to Celestron’s

online technical support center at https://www.celestron.com/pages/technical-support or call 1(800) 421-9649 to receive the number to
be displayed on the outside of your shipping container.

All returns must be accompanied by a written statement setting forth the name, address, and daytime telephone number of the owner, together
with a brief description of any claimed defects. Parts or product for which replacement is made shall become the property of Celestron.

The customer shall be responsible for all costs of transportation and insurance, both to and from the factory of Celestron, and shall be
required to prepay such costs.

Celestron shall use reasonable efforts to repair or replace any telescope covered by this warranty within thirty days of receipt. In the event
repair or replacement shall require more than thirty days, Celestron shall notify the customer accordingly. Celestron reserves the right to
replace any product which has been discontinued from its product line with a new product of comparable value and function.

This warranty shall be void and of no force of effect in the event a covered product has been modified in design or function, or subjected
to abuse, misuse, mishandling or unauthorized repair. Further, product malfunction or deterioration due to normal wear is not covered by
this warranty.

CELESTRON DISCLAIMS ANY WARRANTIES, EXPRESS OR IMPLIED, WHETHER OF MERCHANTABILITY OF FITNESS FOR A PARTICULAR USE, EXCEPT AS EXPRESSLY SET FORTH HEREIN. THE SOLE OBLIGATION

OF CELESTRON UNDER THIS LIMITED WARRANTY SHALL BE TO REPAIR OR REPLACE THE COVERED PRODUCT, IN ACCORDANCE WITH THE TERMS SET FORTH HEREIN. CELESTRON EXPRESSLY DISCLAIMS ANY

LOST PROFITS, GENERAL, SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES WHICH MAY RESULT FROM BREACH OF ANY WARRANTY, OR ARISING OUT OF THE USE OR INABILITY TO USE ANY CELESTRON

PRODUCT. ANY WARRANTIES WHICH ARE IMPLIED AND WHICH CANNOT BE DISCLAIMED SHALL BE LIMITED IN DURATION TO A TERM OF TWO YEARS FROM THE DATE OF ORIGINAL RETAIL PURCHASE.

Some states do not allow the exclusion or limitation of incidental or consequential damages or limitation on how long an implied warranty
lasts, so the above limitations and exclusions may not apply to you.

This warranty gives you specific legal rights, and you may also have other rights which vary from state to state.

Celestron reserves the right to modify or discontinue, without prior notice to you, any model or style telescope.

If warranty problems arise or if you need assistance in using your product, please visit Celestron’s online technical support center at
https://www.celestron.com/pages/technical-support, or call 1(800) 421-9649.

NOTE: This warranty is valid to U.S.A. and Canadian customers who have purchased this product from an authorized Celestron dealer in the U.S.A. or Canada. Warranty outside the U.S.A. and Canada is valid only to

customers who purchased from a Celestron’s International Distributor or Authorized Celestron Dealer in the specific country. Please contact them for any warranty service.

FCC NOTE: This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to part 15 of the FCC Rules. These limits
are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses, and can radiate radio
frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is
no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which
can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one or more of the following measures:

• Reorient or relocate the receiving antenna.

• Increase the separation between the equipment and receiver.

• Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.

• Consult the dealer or an experienced radio/TV technician for help.

Product design and specifications are subject to change without prior notification.
This product is designed and intended for use by those 14 years of age and older.

© 2019 Celestron • All rights reserved
www.celestron.com
2835 Columbia Street • Torrance, CA 90503 U.S.A.
Telephone: [phone]

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Printed in China

01-19