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CHAPTER

2

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11

TELESCOPE FUNDAMENTALS

THE ELECTRONIC CONTROLLER

Briefly described on page 6, the Electronic Controller is the
primary device used to move ETX model telescopes. Electronic
Controller functions include: 

• Slewing the telescope (see Observing with the Electronic

Controller, page 6)

• Turning on the telescope motor drive to automatically track

celestial objects (when the telescope is polar aligned)

• Changing the hemisphere of operation, when required

• Changing tracking speed (see APPENDIX A, page 22)

Modes of Operation

The Electronic Controller can be set to operate in either of two
primary modes: the Alt/Az mode (used when the telescope is
operated in the altazimuth configuration; see page 9) and the
polar mode (used when the telescope is polar-aligned; see page
10).

• Alt/Az (altitude-azimuth, or vertical-horizontal) mode should

be chosen for all terrestrial operations of the telescope. In the
Alt/Az mode you can use the arrow keys  to slew the
telescope to terrestrial or astronomical objects and, once you
locate them, you can follow these objects if they move.
However, in this mode astronomical tracking is not automatic
and  requires  continuous  key  pushes.  The  Electronic
Controller is factory pre-set to the Alt/Az mode.

• Polar mode should be chosen in cases where the telescope

is equipped with either the optional #880 (ETX–90EC) or #881
(ETX-125EC) Table Tripod, or #883 Deluxe Field Tripod,
permitting polar alignment of the telescope for extensive
astronomical observations. In this mode you can use the
arrow keys to slew the telescope to objects, as in the Alt/Az
mode above. In addition, the telescope’s internal motor drive
is turned on, enabling fully automatic tracking of celestial
objects.

The  following  two  methods  are  available  to  change  the
Electronic Controller between the Alt/Az and polar modes:

1. Physically remove one of the mode screws (see Using the

Mode Screws, below).

2. Use the MODE key on the Electronic Controller, as described

in Electronic Controller Modes, opposite.

Using the Mode Screws

You can remove the two screws on the bottom rear of the
Electronic Controller handbox to change the default mode of the
Electronic Controller to Alt/Az or polar and, if polar, to the
hemisphere in which you are located.

NOTE:Mode screws A and B are the outer screws in the recess
directly under the letters A and B on the rear of the Electronic
Controller. Do not remove either of the inner two screws in the
recess.

Mode Screw A (1, Fig. 12): Remove mode screw A to make the
Northern hemisphere polar mode the automatic default of the

Electronic Controller when power is applied (i.e., the motor drive
is activated for operation in the Earth’s Northern Hemisphere —
the U.S.A., Europe, Japan, etc.).

Mode Screw B (2, Fig. 12): Remove mode screw B to to make
the  Southern Hemisphere polar mode the automatic default of
the Electronic Controller when power is applied (i.e., the motor
drive  is  activated  for  operation  in  the  Earth’s  Southern
Hemisphere — Australia, South America, Africa, etc.).

NOTES:(1) Leaving both A and B screws in place (or removing
both screws) keeps the telescope in its original Alt/Az mode.
(2) Removing either A or B screw affects only the telescope’s
default  mode; you may still make mode changes at will during
telescope  operation  using  the  MODE key  (see  E l e c t ro n i c
Controller Modes
, below).

Electronic Controller Modes

The Electronic Controller is in the Alt/Az mode when activated,
unless a mode screw has been removed. To use the Electronic
Controller to change to Northern or Southern Hemisphere polar
mode, or to use Alt/Az mode with one of the mode screws
removed, use the following procedure:

1.

Complete the Polar Alignment Procedure on page 12.

2.

Complete  steps  2  through  8  in  O b s e rving  with  the
Electronic Controller 
(page 7) to initialize the Electronic
Controller.

3.

Press and hold the MODE key (5, Fig. 6) until lights
1 and 2 are on steady and lights 3 and 4 start
blinking.

4.

Press the SPEED key (3, Fig. 6) once. This changes
the system to polar mode for the Earth’s Southern
Hemisphere, with the motor drive set to operate at
the sidereal rate.

5.

Press the SPEED key a second time. This changes
the system to polar mode for the Earth’s Northern
hemisphere, with the motor drive set to operate at
the sidereal rate.

6.

Press the SPEEDkey a third time and the system
returns to the Alt/Az mode. In the Alt/Az mode the
motor drive does not activate when exiting from the
Mode function.

7.

Use the SPEED key as described in the above
steps to cycle among these three modes (Alt/Az,
Southern  Hemisphere  polar,  or  Northern  Hemi-
sphere polar) until the desired mode is shown by the
appropriate light configuration.

8.

Press and hold the MODEkey until just one light is
on. This exits the Mode function. If you choose
Northern or Southern Hemisphere polar mode, the
motor drive starts operating at the sidereal rate.

9.

Use the four arrow keys (1, Fig. 6) to slew the
telescope to the desired object. To change the slew
speed, press the SPEED key.

N OT E : See  APPENDIX  A (page  22)  for  adva n c e d
functions of the Electronic Controller.

Fig.12: Mode screws on rear of Electronic Controller.
(1) Mode .screw A; (2) Mode screw B.

1

2

Summary of Contents for ETX-125EC

Page 1: ...Meade Instruments Corporation Instruction Manual ETX 90EC Astro Telescope ETX 125EC Astro Telescope ...

Page 2: ...ob 10 Horizontal or Right Ascension lock 11 Computer control panel 12 Drive base 13 Hole cover for optional tripod legs 2 14 Right Ascension R A setting circle 15 1 4 20 photo tripod adapter block 16 Flip mirror control knobs 17 Photo port 18 Declination Dec setting circle on left fork arm 19 Viewfinder alignment screws 20 Viewfinder bracket 21 Electronic controller with attached coil cord 3 20 Fi...

Page 3: ... Helpful Charts 23 Latitude Chart for Major Cities of the World 23 Star Locator 23 Appendix C Precise Polar Alignment Setting Circles 24 Precise Polar Alignment 24 Setting Circles 24 Appendix D Road Map to the Stars 25 Appendix E You and the Universe 26 z 3 CONTENTS WARNING Never use a Meade ETX Astro Telescope to look at the Sun Looking at or near the Sun will cause instant and irreversible damag...

Page 4: ...Controller Press any key and the motors briefly move the telescope The Electronic Controller is now operational Use the arrow keys H of the Electronic Controller to move the telescope up and down and or left and right To change the telescope s slew speed press the SPEED key I The indicator lights signify the speed with the upper light showing the highest speed Each press slows the speed down one l...

Page 5: ...ly a few minutes When first opening the packing box note carefully the following parts The ETX Astro Telescope with fork mount system Electronic Controller with attached coil cord Viewfinder packed in a separate small box Super Plössl SP 26mm eyepiece packed in a plastic storage container in a separate small box Hex wrench set 2 wrenches packed with the manual The viewfinder is packed separately f...

Page 6: ... counterclockwise to focus on near objects Flip Mirror Control 16 Fig 1 Both ETX models include an internal optically flat mirror With the flip mirror control in the up position as shown in Fig 1 light is diverted at a 90 angle to the eyepiece Alternately with the flip mirror control in the down position light proceeds straight through the telescope and out the photo port 17 Fig 1 for telephoto or...

Page 7: ...ope see Aligning the Viewfinder page 8 Practice focusing on the object using the focus knob 9 Fig 1 and centering the object in the eyepiece using the Electronic Controller arrows keys 1 Fig 6 Observing with the Electronic Controller With the Electronic Controller in the factory pre set Alt Az vertical horizontal mode the Electronic Controller arrow keys permit pushbutton movements slewing of the ...

Page 8: ...er ETX 125EC Turn the focus ring 2 Fig 7 at the base of the viewfinder eyepiece 3 Fig 7 in either direction until a sharp focus is reached Aligning the Viewfinder In order for the viewfinder to be useful it must first be aligned with the main telescope so that both the viewfinder and the main telescope are pointing at precisely the same location To align the viewfinder follow this procedure 1 The ...

Page 9: ...he eyepiece a design specifically intended for high performance telescopes and one which yields a wide comfortable field of view with extremely high image resolution Technical note to the advanced amateur astronomer The SP 26mm eyepiece supplied with the Meade ETX 90ECand ETX 125EC is a special low profile version of the standard Meade SP 26mm eyepiece which is about 1 4 6mm shorter than the stand...

Page 10: ... early morning hours before the ground has built up internal heat produces better viewing conditions than during late afternoon hours Astronomical Observing Used as an astronomical instrument either ETX model has many optical and electromechanical capabilities In astronomical applications the extremely high level of optical performance of both ETX telescopes is readily visible The range of observa...

Page 11: ...12 Remove mode screw A to make the Northern hemisphere polar mode the automatic default of the Electronic Controller when power is applied i e the motor drive is activated for operation in the Earth s Northern Hemisphere the U S A Europe Japan etc Mode Screw B 2 Fig 12 Remove mode screw B to to make the Southern Hemisphere polar mode the automatic default of the Electronic Controller when power is...

Page 12: ...al equator Objects located further and further east of the prime R A grid line 0hr 0min 0sec carry higher R A coordinates Declination The celestial analog to Earth latitude is called Declination Dec It is measured in degrees minutes and seconds e g 15 27 33 Dec shown as north of the celestial equator is indicated with a plus sign e g the Dec of the North celestial pole is 90 Dec south of the celes...

Page 13: ...reading e g the scale faces the drive base This situation can be remedied by unthreading the leg removing the thumbscrew rotating the inner leg 180 then reinserting the thumbscrew The scale should now be readable when threaded back into the telescope base 7 Loosen the vertical and horizontal locks 6 and 10 Fig 1 and rotate the telescope so that it is oriented as shown in Fig 16 Tighten the vertica...

Page 14: ...ing across the surface These lines are cloud bands in the atmosphere Four of Jupiter s 16 moons Io Europa Ganymede and Callisto can be seen as star like points of light when you use even the lowest magnification The number of moons visible on any given night changes as they circle around the giant planet Saturn is nine times the diameter of Earth and appears as a small round disk with rings extend...

Page 15: ...l table tripod specific to your model of ETX or the 883 Deluxe Field Tripod as a platform for the telescope At effective focal lengths of 1250mm to 1450mm ETX 90EC or 1900mm to 2310mm ETX 125EC even small external vibrations can easily ruin an otherwise good photo CAUTION With the 64 T Adapter and a camera body mounted to the ETX photo port the telescope can be rotated vertically only 45 Moving pa...

Page 16: ... mode directly from the display of a personal computer With the Meade astro software loaded into the PC and with the PC connected to the telescope through Autostar s RS 232 serial interface using the 505 Cable Connector Set included with each astro software package the observer can point and click on any object shown on the PC display The telescope then slews to the object at a speed of 5 per seco...

Page 17: ...e Balance Weight for ETX 90EC If the ETX 90EC is to be used with the 880 Table Tripod and polar aligned at latitudes below 30 the telescope can become unbalanced particularly if heavier accessories e g a camera body are attached to the eyepiece end of the telescope The low latitude balance weight 4 Fig 28 slides onto the standard tripod leg and enables rock solid stability of the telescope even at...

Page 18: ...l and supplies 12vDC directly from the car battery 1244 and 1247 Electric Focusers Meade engineered for smooth rapid focusing with both ETX models each electric focuser Fig 33 includes coarse and micro fine speeds The standard equipment hand controller accepts one user supplied 9 volt battery On both ETX models the focuser plugs into and is powered by the telescope s control panel with operation e...

Page 19: ...pe s internal lubrication and electronic circuitry 9 A set of two English format hex wrenches is provided with both ETX models These wrenches are used as follows Small wrench 05 Use the small wrench to tighten the set screws of any knobs that may loosen e g the focus knob or flip mirror control knob Medium wrench 1 16 This wrench is used to detach the viewfinder bracket from the telescope s rear c...

Page 20: ... page 9 If inside a warm house or building move outside Interior air conditions may distort terrestrial or celestial images making it difficult if not impossible to obtain a sharp focus For optimal viewing use the telescope outside in the open air instead of observing through an open or closed window or screen If viewing a land object on a warm day heat waves will distort the image see Terrestrial...

Page 21: ...pe shipping weight 5 8kg 12 8 lbs Battery Life approx with Electronic Controller 45 hrs with Autostar 20 hrs Specifications ETX 125EC Astro Telescope Optical design Maksutov Cassegrain Primary mirror diameter 138mm 5 43 Clear aperture 127mm 5 0 Focal length 1900mm 74 8 Focal ratio photographic speed f 15 Near focus approx 5 5m 18 ft Resolving power 0 9 arc secs Super multi coatings EMC standard Li...

Page 22: ...T key 5 Press and hold the MODE key until only a single light is on This exits the Mode function If Northern or Southern Hemisphere polar mode was chosen the motor drive starts operating at the sidereal rate 6 Use the four arrow keys 1 Fig 6 to slew the telescope to the desired object To change the slew speed press the SPEED key Southern Hemisphere Polar 1 Press and hold the MODE key 5 Fig 6 until...

Page 23: ...any 50 N Glasgow Scotland 56 N Helsinki Finland 60 N Lisbon Portugal 39 N London England 51 N Madrid Spain 40 N Oslo Norway 60 N Paris France 49 N Rome Italy 42 N Stockholm Sweden 59 N Vienna Austria 48 N Warsaw Poland 52 N Star Locator Following is a list of bright stars with their R A and Dec coordinates along with the Northern hemisphere season when these stars are prominent in the night sky Th...

Page 24: ...etting Circle Since celestial objects move in R A the R A setting circle Fig 36 must be reset as each object is located during an observing session The R A pointer is located on the drive base 90 counterclockwise from the telescope s computer control panel 11 Fig 1 immediately under the R A circle NOTE The R A circle has two rows of numbers from 0 to 23 corresponding to the hours of a 24 hour cloc...

Page 25: ...orthernmost point of the celestial sphere Extending from Polaris is the Great Square shared by the constellation Pegasus and Andromeda Within Andromeda is the Andromeda Galaxy the closest large galaxy to our solar system at about 2 2 million light years away The Summer Triangle is a notable region in the sky to the left of the handle of the Big Dipper The triangle is made up of three very bright s...

Page 26: ...iptical orbitis eccentric and carriesthe planet inside theorbit ofNeptune at itsclosest approachto theSun The distance from the Sun to the nearest star is about 4 3 light years or 25 trillion miles This distance is so large that if a scale model were created with the Earth one inch away from the Sun the nearest star would have to be placed over 4 miles away Approximately one hundred billion stars ...

Page 27: ... from state to state Meade reserves the right to change product specifications or to discontinue products without notice This warranty supersedes all previous Meade product warranties WARNING 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 ...

Page 28: ...0 ETX is a registered trademark of Meade Instruments Corporation Part no 14 1010 20 Meade Instruments Corporation 6001 OAK CANYON IRVINE CALIFORNIA 92618 5200 U S A 949 451 1450 FAX 949 451 1460 www meade com ...

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