ASTRO-PHYSICS 900GTO Assembly Manual
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ASTRO-PHYSICS 900GTO Assembly Manual

German equatorial with gtocp3 servo motor drive for mount shipped starting in may 2008 beginning with serial number 900706
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Summary of Contents for ASTRO-PHYSICS 900GTO

  • Page 2: Table Of Contents

    ASTRO-PHYSICS 900GTO GERMAN EQUATORIAL WITH GTOCP3 SERVO MOTOR DRIVE 900GTO P ODEL ARTS EATURES AND PECIFICATIONS NTRODUCTION Why Polar Alignment is Important SSEMBLY NSTRUCTIONS Before You Leave Home Gross Latitude Adjustment Assemble Pier (purchased separately) Attach Pier Adapter to Pier Post...
  • Page 3 Prevent the Cables From Tangling 900 Motor Cables Accessory Cables Removing the GTO Control Box from the 900GTO Mount GTO K EYPAD ONTROLLER PERATION LEWING OUNT IN ELOW REEZING EMPERATURES OUNT LEANING AND AINTENANCE Care Cleaning and Touch-up Mount Maintenance...

  • Page 4: Astro-Physics

    For a complete listing of our 900GTO accessories, visit our website – www.astro-physics.com Note on Encoders: Mounted encoders can no longer be used with the 900GTO (for mounts shipped starting in October, 2005 – beginning serial number 900451) because of the R.A. shaft re-design. They are not needed since the go-to functions of the mount are so much more accurate.

  • Page 5: Features And Specifications

    Capacity of Mount: Approximately 70 lbs. (31.8kg) - telescope and accessories (not including counterweights), depending on length. Will accommodate Astro-Physics and similar refractors up to 180mm f9, 12" Cassegrains, 12-14" Ritchey-Chretiens. These are only guidelines. Some telescopes are long for their weight or very heavy for their size and will require a larger mount.

  • Page 6: Introduction

    2008. The periodic error of your 900GTO will be 7 arc seconds or less (before correction). We have already loaded the PEMPro curve that was generated during your mount’s testing into the servo to reduce the error even further, and to give you a head start right out of the box.

  • Page 7: Assembly Instructions

    ASSEMBLY INSTRUCTIONS Please read all instructions before attempting to set up your 900GTO mount. The model 900 is very rugged, however like any precision instrument, it can be damaged by improper use and handling. Please refer to the following illustrations. The parts are labeled so that we can establish common terminology.

  • Page 8: Before You Leave Home

    Before You Leave Home Since most of us must set up our instruments in the dark, in the cold or while battling mosquitoes, a bit of preplanning and organization is important. There are a few simple things that can be accomplished in the comfort of your home before heading outside.
  • Page 9 Determine the latitude range that you need and position the altitude adjuster bar so that the hole that is marked “A”, as shown in the diagram, is located at the appropriate hole position numbered 1-4 in the lower diagram. Note that hole “A”...

  • Page 10: Assemble Pier (Purchased Separately)

    Hi-Lo Latitude Wedge and pier adapters from earlier production runs do not have the thru-holes. They require the Flat Surface Adapter for mounting onto a flat surface. Note that with the Astro-Physics pier, you can orient the pier adapter so that one of the pier legs faces "north"...

  • Page 11: Standard Pier Adapter (900Spa)

    This pier adapter was designed for very accurate and smooth adjustment of the azimuth angle without loosening the lock- down knobs on the base of the mount. The top plate of the adapter rotates through the 900GTO mount’s full 15 degrees of azimuth motion.

  • Page 12: Hi-Lo Latitude Wedge Pier Adapter Assembly For 0 - 20° Or 68° - 88° Latitude - North Or South (900Wdga)

    Block on the low side. For extreme polar latitudes, the plate on top of the wedge can be turned around to extend the useful range of your 900GTO above 68° latitude. Simply remove the two side knobs and then remove the six screws that attach the flat plate to the wedge. Rotate the flat plate 180° and re-assemble with the Azimuth Adjuster Block on the high side.

  • Page 13: Altitude And Azimuth Adjustments - Rough Polar Alignment

    However, we found that the inevitable backlash in this type of system made adjustment more problematic and less precise. The way to use the Astro-Physics Heavy Duty Azimuth Adjuster with its clear registration marks for fine adjustment is to back off one of the knobs by a set amount (a certain number of registration marks) and then to turn the other knob until you re-establish contact on both sides of the Azimuth Adjuster Block.

  • Page 14: Assemble Declination Axis

    Altitude (latitude) adjustments: Loosen the altitude locking knobs. Move the polar axis up or down with the large altitude adjustment knob located in the front of the polar axis assembly. The tommy bar can be positioned in any of the threaded holes located in the altitude adjustment knob. Use this bar to help you turn the knob. We have found that using the turnbuckle on the north leg of our pier also can make fine altitude adjustments, if used.
  • Page 15 Use with the 7” or 10” sliding bars (SB0800 or SB1000), which are sold separately. Repositioning the sliding bar will aid in adjusting the balance of your instrument. NOTE: This plate requires the use of the Q4047 adapter with the 900GTO mount to provide clearance for the knobs.

  • Page 16: Attach Counterweight Shaft And Counterweights

    We prefer this keyhole method to the standard way of completely removing the screws and possibly dropping them in the grass. Astro-Physics or Losmandy Dovetail Plates: Attach the mounting rings to the male dovetail plate (sliding bar).

  • Page 17: Fine Polar Alignment

    That means that the R.A. axis will be tracking up to the limits of your polar alignment. However, if you plan to use any of the go-to functions of the 900GTO or do astrophotography, you must perform a more accurate polar alignment.

  • Page 18: Balancing Your Telescope

    Now, mount up and balance your telescope so you can "feel" what this resistance in R.A. and Dec. (movement backwards and forwards) is like when you make these motions from the eyepiece end of your telescope as you would during normal use when slewing (pushing) by hand to acquire an astronomical object within the field of view of your finder or scope.

  • Page 19: Servo Motor Drive

    ASCOM compatible telescope software (all purchased separately). The GTO Servo Control Box is mounted directly onto the polar axis of the 900GTO mount. Please remember that this box contains advanced electronics and must be treated with the same care given to other fine equipment. You can see that the unit is built to be rugged, however it is not indestructible.

  • Page 20: 12V Connector

    You must have two serial ports available on your computer to take advantage of this feature. If you use a laptop or a newer desktop computer, you may need to purchase a USB to Serial Adapter. Starting in the spring of 2008, Astro-Physics will begin offering single port and four port units made by Keyspan™...

  • Page 21: Focus Connector

    PEMPro v.2.0 has, of course, been included with your 900GTO, so you can actually produce an even more refined periodic error curve by using more worm cycles than we can do here at the factory. Although we can make no promises, we have...
  • Page 22 International Space Station – Amateur Telescope (ISS-AT) project. This mount is operated remotely and cable management is essential. The same principles apply to the 900GTO. The scope is a modified Celestron C-14 and the accessories included: CCD camera, color filter wheel, remote focuser and a Kendrick Dew Remover.
  • Page 23 Allen head bolts. This allowed the Dec cable to slide easily over the axis in all orientations and there was no snagging of the wire anywhere. Please call Astro-Physics if you would like to order these bolts. Do NOT try to install normal Allen head bolts, they must be modified.
  • Page 24 Care Although we build it to be rugged enough for field use, your 900GTO is a precision instrument with very accurate worm and wheel adjustments. Please be careful if you place the mount on a flat surface, i.e. the ground or trunk of your car. The gear alignment may be affected if the R.A.
  • Page 25 The members of this group are very knowledgeable about the operation of their mounts, CCD imaging and other related issues. The staff of Astro-Physics also participates and you will find a wealth of information in the archives.
  • Page 26 What is the maximum voltage that I can use to power the servo drive? The servo drive of the Mach1GTO, 900GTO and 1200GTO will withstand up to 24 volts without any sort of damage to the internal electronics, according to our engineer. However, above about 17 volts, the motors may become a bit jittery because of the higher gain with this much voltage.
  • Page 27 RECOMMENDED READING FROM OUR STAFF: The Backyard Astronomer's Guide, Terence Dickinson and Alan Dyer, Firefly Books Ltd., Rev. Ed., Oct. 2002. ISBN 155209507X The authors, both former editors of Astronomy magazine, offer practical insight into astronomical equipment, finding your way around the sky, polar alignment, using setting circles, and astrophotography. This book provides excellent explanations and is well organized and illustrated.
  • Page 28 STANDARD PIER ADAPTER FOR THE 900GTO MOUNT The 900 series mount is designed to fit into our 8" outside diameter pier which is available in several heights. The pier adapter of the 900 mount shown above fits into the post (aluminum tube) of the pier assembly and is secured with six (6) 5/16-18 screws at the location marked C.
  • Page 29 USEFUL DIMENSIONS FOR OBSERVATORY PLANNING People often ask us what the 900GTO's dimensions are. The answer is: It depends. Different latitude settings can drastically affect the shape and dimensions of the mount. To answer this question we have prepared the following diagram. Your PulseGuide CD also has an Excel spreadsheet for calculating these and additional dimensions for your own latitude and system.
  • Page 30 • A special screwdriver that has been modified by Astro-Physics, if you ordered it. This screwdriver is marked with masking tape. DO NOT REMOVE this tape. Instructions for making your own tool can be found below and in the Technical Support section of our website.
  • Page 31 Construct Your Own Clutch Plug Extraction Tool...
  • Page 32 CHARACTERIZING THE DEC AXIS MOTIONS...
  • Page 33 Astro-Physics Mounting Plate Fastener Chart A-P Part # Description Ships with: (4) 1/4-20x5/8" SHCS [for mounting to 400, 900 or Mach1GTO] FP1500 15" Flat Plate (4) M6-1.0x20mm SHCS [for mounting to 600E] (4) 1/4-20x3/4" SHCS [for mounting to 1200] (6) 1/4-20x1" FHSCS [for mounting to 900 or 1200] FP1800 18"...

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