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ASTRO-PHYSICS 900GTO Manual

German equatorial with gtocp3 servo motor drive
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Summary of Contents for ASTRO-PHYSICS 900GTO

  • Page 2: Table Of Contents

    INTRODUCTION Why Polar Alignment is Important ASSEMBLY DIAGRAM BEFORE YOU LEAVE HOME Gross Latitude Adjustment for 900GTO German Equatorial Mounts Attach Pier Adapter to Pier Post (purchased separately) Standard Pier Adapter (900SPA) Precision-Adjust Rotating Pier Adapter with Azimuth Bearing (900RPA)
  • Page 3 Routine Mount Maintenance TROUBLESHOOTING, TIPS AND SUPPORT Troubleshooting and Tips Additional Support STANDARD PIER ADAPTER OF THE 900GTO MOUNT USEFUL DIMENSIONS FOR OBSERVATORY PLANNING CLUTCH PLUG REPLACEMENT FOR 900 OR 1200 MOUNT Construct Your Own Clutch Plug Extraction Tool CHARACTERIZING THE DEC. AXIS MOTIONS...

  • Page 4: About This Manual

    This version of the 900GTO Manual was prepared for the production run of mounts that began shipping in November of 2011. Most of the information in this manual is applicable to all 900GTO’s that have been produced. Some of the information in this manual was simply not available when the first 900GTO’s left our factory back in 1998.

  • Page 5: Model 900Gto Parts List

    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 6: Mechanical Specifications

    Counterweight shaft: 10.5 lb. (4.8 kg) Approximately 70 lb. (31.8 kg) scope and accessories (not including counterweights), depending on length. Recommended for: Astro-Physics and similar fast refractors up to 180 mm f9, 12” Cassegrains, 12.5” CDKs, 12-14” Ritchey-Chretiens. These are only guidelines.

  • Page 7: Introduction

    GTO Servo Motor Drive System Manual. The 900GTO also includes a full version of PEMPro v.2.x, and as an added bonus, all 900GTO mounts will come pre- loaded with the custom-fitted PEMPro™ corrections from our extensive individual testing that is performed on each and every mount.

  • Page 8: Assembly Diagram

    ASSEMBLY DIAGRAM 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 9: Before You Leave Home

    There are a few simple things that can be accomplished in the comfort of your home before heading outside. Gross Latitude Adjustment for 900GTO German Equatorial Mounts Degree ranges specified below apply to mounts shipped starting in May 2006. Older mounts will have slightly different latitude ranges unless they were upgraded with the taller polar fork.
  • Page 10 point until the corresponding hole lines up. Consult the labeled photo to determine which hole of the altitude adjuster bar should be used. Be very careful since the holes marked C and B are very close to one another, as are the holes marked D and E.

  • Page 11: Attach Pier Adapter To Pier Post (Purchased Separately)

    Attach Pier Adapter to Pier Post (purchased separately) If you purchased the pier from Astro-Physics, the pier adapter of the 900 will attach right to the top of the pier. If you are constructing your own pier or tripod, you will need to incorporate this part. Three models of the pier adapter are now available for use with the 900 from Astro-Physics.

  • Page 12: Precision-Adjust Rotating Pier Adapter With Azimuth Bearing (900Rpa)

    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 13: Hi-Lo Latitude Wedge Pier Adapter Assembly (900Wdga) Or Wedge (900Wdg)

    1/4” ID x 1” OD flat washers, the center pivot screw, six 5/16-18 x 5/8 socket buttonhead screws and six 5/16 x 9/16”OD x 0.060” flat washers, which enable you to attach the pier adapter to your Astro-Physics pier. Please note: 1.

  • Page 14: At Your Observing Site

    Assemble Pier (purchased separately) Begin by assembling the portable pier at the desired observing location. Take note which direction is north. (These instructions are for the Astro-Physics Portable Piers. For other piers, please follow the manufacturer’s instructions.) 1. Slide the three legs onto the nubs of the base...

  • Page 15: Polar Alignment - Part 1 - Rough Alignment

    Pier East of True North - Adjusted West The best adjustment technique to use with 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 16: Assemble Declination Axis

    the precise starting point if for some reason you overshot your mark (or if you adjusted the wrong way), because you know exactly how far you’ve gone. This is explained further in the section on Fine Polar Alignment. 4. 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.

  • Page 17: Attach Mounting Plate

    Several mounting plates (also called cradle or saddle plates) are available for the 900GTO mount. If you own more than one instrument, you may need more than one plate, or you may wish to use one of the dovetail mounting plate options with more than one male dovetail sliding bar.

  • Page 18: Losmandy D-Series Compatible Saddle Plates

    Losmandy D-Series Compatible Saddle Plates 8.5” Dovetail Saddle Plate for Losmandy D Series Plates (DOVELM2) This Astro-Physics plate attaches to the 400, 600E, 900 and 1200 mounts. If you already own one of the Losmandy DAP series (fits Astro-Physics refractors), DC series (for Celestron 8”...

  • Page 19: Side-By-Side, Vixen Style And Other Plate Options

    Converter (SBD2V)” on page 18 described below. As an accessory plate - Attach to the top of our Astro-Physics mounting rings (tube diameters 5”-8”) or rings from Parallax Instruments that have the Astro-Physics hole pattern (you can request it). Note, you must also use a sliding bar on the bottom of the rings with the same distance (6.3”...

  • Page 20: Attach Counterweight Shaft And Counterweights

    Other Mounting Plate Options Additional mounting plate options including custom plates may be available from other sources. The hole patterns for the declination hub are shown on the illustration on page 16. Attach Counterweight Shaft and Counterweights IMPORTANT: ● Always attach the counterweights before mounting the telescope to the cradle plate to prevent sudden movement of an unbalanced tube assembly, which may cause damage or injury.

  • Page 21: Clutch Knobs, Balancing And Fine Polar Alignment

    CLUTCH KNOBS, BALANCING AND FINE POLAR ALIGNMENT Understanding the R.A. and Dec. Clutch Knobs We suggest that you read this before assembling the remainder of your system. 1. What do they do? The four R.A. and four Dec. clutch knobs depicted in the Assembly Diagram on page 6 have the function of connecting the R.A.

  • Page 22: Balancing Your Telescope

    Note, however, that this motion will not be accurate enough to qualify as “tracking” without accurate polar alignment. In short, if you will depend on the go-to functions of the 900GTO, or if you intend to do astrophotography, you must perform a more accurate polar alignment.

  • Page 23: Methods For Fine Polar Alignment

    ○ There is a Polar Alignment Wizard in the Full Version of PEMPro™ 2.x that is included with your 900GTO. This wizard is quick and easy and gives excellent results! Details are in the PEMPro™ documentation.

  • Page 24: Making Precise Altitude And Azimuth Adjustments

    The mechanics of altitude and azimuth adjustment are relatively straightforward. In the discussion below, we will provide some information and tips that will give you the greatest success with your 900GTO regardless of the method you choose for determining the amount and direction of each adjustment. We’ll leave the choice of method up to you. (Did we mention...

  • Page 25: Precision-Adjust Rotating Pier Adapter With Azimuth Bearing (900Rpa)

    made adjustment more problematic and less precise. The one-piece Azimuth Adjustment assembly makes for easy and accurate polar alignment in your observatory or in the field, and it eliminates issues of adjustment backlash. The heavy-duty construction and integrated one-piece design result in smooth control of the azimuth axis.

  • Page 26: Azimuth Adjuster Knob Locking Screws

    quickly identify the desired orientation. 1. The altitude axis should be fully locked down with a hex key before adjusting the azimuth. 2. Follow one of the methods of polar alignment mentioned above. 3. During the initial adjustment phase, the front and two side lock-down knobs should be hand snugged only. The rear knob should be relatively tight.

  • Page 27: Cable Management

    Modified R.A. Clutch Set Screws (part # F0021) and a Replacement Assembly for 900/1200 Dovetail Knob (part # DOVEKBREP). Note that these optional items are available for purchase on our Web site or by calling Astro-Physics. Clutch Knobs...

  • Page 28: Example From International Space Station - Amateur Telescope (Iss-At) Project

    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.

  • Page 29: Mount Care, Cleaning And Maintenance

    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 30: Troubleshooting, Tips And Support

    In a few cases, we have seen that the set screw on this spur has backed off and needs to be retightened. If you have any doubts about where this worm and spur gear is in the scheme of things, call Astro-Physics...
  • Page 31 CCD camera will pick it up to give you oval stars - that is a given. What you need to find out is whether this periodic error is within limits (+- 3.5 arcseconds for the 900GTO and +-2.5 arcseconds for the 1200GTO) and whether it is smoothly varying.

  • Page 32: Additional Support

    Additional Support For additional information regarding the 900GTO, refer to the Technical Support Section of our Web site. We also encourage you to participate in the ap-gto user group. The members of this group are very knowledgeable about the operation of their mounts, CCD imaging and other related issues.

  • Page 33: Standard Pier Adapter Of The 900Gto Mount

    STANDARD PIER ADAPTER OF THE 900GTO MOUNT The 900 series mount is designed to fit into our 8” outside diameter pier which is available in several heights. The Standard Pier Adapter for 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 34: Useful Dimensions For Observatory Planning

    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.

  • Page 35: Clutch Plug Replacement For 900 Or 1200 Mount

    What you will find in this package: ● 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 Web site.

  • Page 36: Construct Your Own Clutch Plug Extraction Tool

    Construct Your Own Clutch Plug Extraction Tool...

  • Page 37: Characterizing The Dec. Axis Motions

    CHARACTERIZING THE DEC. AXIS MOTIONS These instructions explain how to use MaxImDL™ software as a tool for characterizing any problems with the Declination axis movements of your mount. However, Ray Gralak’s PulseGuide™ software offers an easier and more extensive evaluation proceedure. PulseGuide™ is available as a free download through our Web site. Step 1 Acquire a reasonably bright guide star and begin guiding in R.A.

  • Page 38: Astro-Physics Mounting Plate Fastener Chart

    12" Losmandy D-Series Male to Vixen Style SBD2V (Losmandy V-Series) Female Adapter / Sliding Bar (1) 1/4-20x1/4" SHCS [Safety Stop for SBD2V] (3) 5/16-18x5/8" SHCS Losmandy Tripod to Astro-Physics Mount Adapter (4) 1/4-20x5/8" SHCS LT2APM Plate (4) 1/4-20x1" SHCS (3) 3/8-16x3/4 SHCS CBAPT, (1) 1/4-20X3/4"...

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