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GTOCP2
User Manual
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Socket Mobile GTOCP2 User Manual

ASTRO-PHYSICS
1200 GERMAN EQUATORIAL WITH
GTO SERVO MOTOR DRIVE
Model GTOCP2
February 26, 2002
2
ASTRO-PHYSICS
1200 GERMAN EQUATORIAL WITH
GTO SERVO MOTOR DRIVE
Why Polar Alignment is Important 6
Compensation for the Earth’s rotation 6
Before You Leave Home 7 Before You Leave Home 8
Gross Latitude Adjustment 8
Attach Pier Adapter to Pier Post 9 Assemble Pier (purchased separately) 9 Assemble Polar Axis Assembly to Pier or Tripod 10 Altitude and Azimuth Adjustments - Rough polar alignment 10 Assemble Declination Axis 11
Removing Declination Axis at the End of your Observing Session 11 Attach Mounting Plate (purchased separately) 12 Attach Mounting Rings (purchased separately) 13 Fine Polar Alignment 13
Methods for fine polar alignment 13
Altitude and Azimuth Adjustments 13
R.A. and Dec. Damper Knobs 14 R.A. and Dec. Clutch Knobs 14 Balancing Your Telescope 14
GTO Control Box – Model GTOCP2 16
R.A. and Dec. Cable Connections 16
12V Connector 16
POWER Indicator Light 16
KEYPAD Connector 16
RS-232 Connectors 17
FOCUS Connector 17
RETICLE Connector 17
AUTOGUIDER Connector 17
+6V Connector 17
N and S Switch 17 Prevent the Cables from Tangling 18
1200 Motor Cables 18
Accessory Cables 18 Removing the GTO Control Box From 1200 Mount 18 GTO Keypad Controller Operation 18
3
Fitting Declination Encoder Housing 21 Fitting Right Ascension Encoder Housing 22 Periodic Maintenance 22
4
ASTRO-PHYSICS
1200 GERMAN EQUATORIAL WITH
GTO SERVO MOTOR DRIVE

MODEL 1200GTO PARTS LIST – MODEL GTOCP2

1 Polar axis assembly (right ascension-R.A.) with Servo Box GTOCP2 1 Declination (Dec.) axis assembly 1 Pier top adapter with six (6) 5/16-18 x 5/8" button head screws with washers (these may be attached to your pier post if you ordered one) 1 Stainless counterweight shaft with washer stop and black plastic knob (knob has 5/16 thread) 1 Y cable – R.A. portion is 12.5” long and Dec portion is 37.5” long 1 D.C. power cord (cigarette lighter adapter on one end) - 8’ long 1 GTO Keypad controller with 15’ coiled cable 1 Keypad Protector (KEYPRO) 1 DigitalSky Voice Software (CD-ROM) 1 Hex key set 2 8-32 thumbscrews (substitute these for 8-32 set screws that hold GTO Servo Control Box in place, if you wish)
In order to fully assemble your mount, you will need the following items sold separately: mounting plate, 10” O.D. pier, counterweights, and portable rechargeable battery pack (or 110 to 12V DC converter). Several sizes and types are available for your selection. Many of these items will be discussed throughout these instructions.
Several additional options are available:
Longer counterweight shaft – 27” useable length, part # M12661 Santa Barbara Instrument Group CCD Imaging cameras and ST-4 Autoguider or STV - if you plan to pursue CCD
imaging or astrophotography Pier accessory trays for 10” pier and support bars - handy to keep your eyepieces close at hand Polar axis telescope - threads into the base of the polar axis assembly. Many users find a polar axis telescope useful for
zeroing in on the pole quickly, particularly with telescopes that are not orthogonal to the mount. Mounted encoders – Although you can use these with your mount, they are not necessary since the go-to functions of
the mount are more accurate. The 4000 steps of the encoders, which read the position of the shaft are very
coarse (324 arc seconds) while the encoder that is built into the servo motor itself is 0.05 arc seconds.

FEATURES AND SPECIFICATIONS

R.A. worm wheel: 10.3”, 225-tooth aluminum Dec worm wheel: 7.2”, 225-tooth aluminum Worm gear: Brass R.A. shaft: 3.35” diameter R.A. thrust bearings: 9.5” diameter Dec shaft: 2.36” diameter Dec thrust bearings: 6.5” diameter Counterweight shaft: 18” useable length,
1.875” diameter, stainless steel, removable Latitude range: 20 to 68 degrees with or without polar scope or encoders attached (if you are above 65° you will have to remove one pier top knob)
Azimuth adjustment: Approximately 14 degrees Setting circles: Porter Slip Ring design, engraved Right ascension: 4-minute increments, pointer Declination: 1-degree increments, pointer Motors: Zero-cogging servo motors Power Consumption: 0.4 amps at the sidereal rate 3 amps both motors slewing Power requirements: 12 VDC, range 11.5 to 15 Weight of mount: total -91 lbs. Dec axis - 30 lbs. R.A axis - 47 lbs. counterweight shaft -14 lbs.
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INTRODUCTION

The 1200 German equatorial was designed to meet the needs of the advanced observer who requires a mount with maximum strength and rigidity and minimum weight. The excess material in both axes has been carved out while retaining a heavily ribbed structure for internal strength and rigidity. A unique dovetail was machined into the mating surfaces of the R.A. and Dec axes. This feature allows quick and easy assembly in the field without any tools.
The DC servo motor drive with GTO computer system, including the keypad controller with its digital display screen and DigitalSky Voice software offer extraordinary sophistication for today’s observer. Whether you enjoy visual astronomy exclusively or plan an aggressive astrophotography or CCD imaging program, this mount will allow you to maximize your night out under the stars.
The advanced keypad features allow you to slew automatically to objects in a wide range of databases as well as any RA/Dec coordinate. A large selection of common names for stars and other objects makes your selection a snap. The rapid slew rate of 5 degrees per second (1200x) allows you to locate objects very quickly and accurately. You will be very pleased with the intuitive operation of this controller. There are no complicated sequences of keystrokes to remember. It is so easy to use that even it you don’t use it for a few months, you will feel at home with the keypad very quickly.
DigitalSky Voice software provides additional capabilities to control the movement of your telescope by using two-way verbal communication with a microphone or by a few clicks of your computer mouse (or touchpad). You can remain at the eyepiece while you direct your telescope with verbal commands. There is no need to put a flashlight in your mouth to see the keyboard. You have total control with your voice and/or mouse. Voice control also allows you to retain your dark adaptation.
The 1200 is equally at home in a permanent observatory or as a portable mounting for remote star parties thanks to the ease with which the two axes come apart. This is the perfect mount for a large refractor, Newtonian, Cassegrain or astrograph.
In order to maximize your pleasure on your first night out, we recommend that you familiarize yourself with the assembly and basic operation of the mount indoors. The temperature will be comfortable, the mosquitoes at bay, and you'll have enough light to see the illustrations and read the manual. Please take particular note of counterbalancing, use of the clutches and operation of the keypad controller.

Why Polar Alignment is Important

Compensation for the Earth’s rotation

If you were to take a long exposure photograph with Polaris (often called the north star) in the center of the field, you would discover that all stars seem to revolve around Polaris. This effect is due to the rotation of the earth on its axis. Motor driven equatorial mounts were designed to compensate for the earth's rotation by moving the telescope at the same rate and opposite to the earth's rotation. When the polar axis of the telescope is pointed at the celestial pole (polar aligned) as shown in Diagram 1, the mount will follow (track) the motions of the sun, moon, planets and stars. As a result, the object that you are observing will appear motionless as you observe through the eyepiece or take astrophotos.
Diagram 1
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ASSEMBLY INSTRUCTIONS

Please read all instructions before attempting to set up your 1200 mount. The Model 1200 is very rugged, however like any precision instrument, it can be damaged by improper use and handling. Please refer to Diagram 2 for an illustration of the mount. The parts are labeled so that we can establish common terminology.
The following terms and abbreviations are used interchangeably in these instructions:
polar axis = right ascension axis = R.A. axis = R.A. housing declination axis = dec. axis = dec. housing
Diagram 2
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