900 Mount Upgrades and Spare Parts
Since the introduction of the 900 German Equatorial in late 1994, we have offered successive generations with improvements in both the mechanical construction and drive system. Since our design and production staff includes experienced CCD imagers, we are continually pushing the mounts to the limits of performance. Equally important, our customers have offered valuable feedback and suggestions throughout the years.
We are pleased to offer a variety of upgrades and spare parts so that you can obtain maximum performance from the 900 mount that you own. Some of these upgrades are available for all 900s and some are appropriate to particular models, but not others. Please check the product descriptions carefully to determine if a particular upgrade or component can be used with your mount. If you are confused by the HDA, QMD, SMD and GTO designations of the 900 mounts, please refer to a brief history of all 900 models. If you require a spare part not listed below, please do not hesitate to call.
900 Precision-Adjust Rotating Pier Adapter with Azimuth Bearing (900RPA)
|The new pier adapter rotates on
a bearing surface for ultra-smooth operation.
This allows you to lock the mount down with no
need to loosen the base during azimuth adjustment.
The top plate of the adapter rotates through the 900GTO mount’s full 15 degrees of azimuth motion. (It does not rotate through a full 360 degrees!) This option is especially recommended for use
in the field. You may wish to purchase two or
more of these assemblies to install on separate
piers. Perhaps you have a permanent observatory
and a portable pier for traveling to dark sky
sites. The Standard 900 Pier Adapter (900SPA)
is another option to consider.
More information and Instructions (PDF)
The Precision-Adjust Rotating Pier Adapter includes two machined plates, four machined aluminum lock knobs with 1/4 ID x 1"OD flat washers, 1.9" azimuth adjuster block, six 5/16-18 x 5/8" socket buttonhead screws and 5/16 x 9/16"OD x 0.060" flat washers. All machined parts are black anodized and the fasteners are stainless steel. This adapter will mount directly into an Astro-Physics Portable Pier.
Mounts: All 900 mount models (HDA,
QMD, SMD and GTO) that have been produced.
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900 Hi-Lo Latitude Wedge (900WDG) and Wedge Assembly (900WDGA) for 0-20 or 68-88 Latitude
|If your latitude is below 20 or above 68 degrees, one of these wedges will allow you to place your 900 mount in the proper position for polar alignment. You will use the wedge in place of the Standard Pier Adapter (900SPA) or Precision-Adjust Rotating Pier Adapter (900RPA) shown above. The 900 Wedge Assembly (900WDGA) comes complete with the azimuth adjustor block, the center pivot screw and the four locking knobs with their hardened washers. Those of you who already have a Standard Pier Adapter can order the 900 Wedge by itself (900WDG). Just transfer the azimuth adjustor block, the center pivot screw and the four locking knobs supplied with your original adapter to this wedge and bolt it onto your pier. Both of the wedge pier adapter configurations include 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 that this adapter must fit inside another part and be bolted from the side. It cannot be bolted directly onto a flat surface. For custom installations onto a flat surface, insert the 900WDG into our our 900 Flat Surface Adapter (900FSA), which has been bolted to the flat surface of your pier.
The 900 Hi-Lo Latitude Wedge can be set up for either tropical (0-20 deg.) or polar (68-88 deg.) latitudes. Simply remove the 6 screws that attach the flat plate, rotate the plate so the Azimuth Adjuster Block will either be on the low side (tropical 0-20 deg.) or on the high side (polar 68-88 deg.) and re-assemble.
The 900 Hi-Lo Latitude Wedge can also be used with the 900
Precision Adjust Rotating Pier Adapter (900RPA) to make polar alignment
easier for mounts used in the field. The Wedge has been drilled and
tapped to accept the 900 Flat Surface
Adapter (900FSA). Attach the Flat Surface Adapter to the top of
the Wedge with four 1/4 - 20 x 3/4" socket head cap screws (not
included). If you have the 900 Wedge Assembly, just remove the four
Locking Knobs and the Azimuth Adjuster Block and leave the center pivot
screw in place so it won't get lost! Then install the Precision Adjust
Rotating Pier Adapter into the Flat Surface Adapter. Note: The photo
is of an earlier version and does not show the holes that accept the
flat surface adapter.
Back to top900 Flat Surface Adapter (900FSA)
Use this Flat Surface Adapter to attach either the Precision-Adjust Rotating Pier Adapter (900RPA) or the Hi-Lo Latitude Wedge (900WDG) to a flat plate on your custom made pier or tripod. You can also use it with the Standard Pier Adapter (900SPA) to give a more finished appearance.
The 900 Flat Surface Adapter is precision machined aluminum. It has been polished smooth and then anodized black.
The Flat Surface Adapter bolts onto the flat plate on top of your pier or tripod, then the Pier Adapter or Hi-Lo Latitude Wedge simply slips in (just as it fits into our pier) and you fasten from the side with the six screws and washers provided with the Pier Adapter.
The bolt circle for attaching the 900 Flat Surface Adapter to your pier is 7.230" in diameter. This is the same size bolt circle as is found on our Standard Pier Adapter (900SPA), so if you are replacing a Standard Pier Adapter with a Rotating Adapter or Wedge, you can use the same holes. The holes in your flat mounting surface must form a square with sides running east - west and north - south as opposed to a diamond (45° rotation) with diagonals running east - west and north - south.
Mounts: All 900 mount models (HDA, QMD, SMD and GTO) that have been produced and the 1100GTO mount. Note: although the older 800 mounts had the same diameter base as the 900 series, their bases are too thick for this adapter. DO NOT purchase this adapter for an 800 mount!
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Right-Angle Polar Alignment Scope Adapter for 900GTO (RAPAS-900)
This adapter fastens to the polar axis rear plate on the 900 mount, allowing use of our Right-Angle Polar Alignment Scope (RAPAS). The RAPAS can be used with all 900 mounts. This adapter is push/pull adjustable for precise alignment. Once adjusted, it will retain its precision, allowing the polar alignment scope to be removed and re-inserted as needed. Includes three replacement (longer) socket head cap screws. Please see this link for additional information.
Pier Adapter Knob Kit for 900
||This kit contains four machined and black anodized Pier Adapter Knobs and 1/4" ID x 1" OD flat washers. If you do not purchase one of our pier adapters shown above, for instance, if you purchase the Monolith Pier from Particle Wave Technologies, you will need these knobs to attach your mount to the Monolith.
The kit can also be purchased as spares if you lose or damage the knobs that came with your Standard Pier Adapter (900SPA) or Precision-Adjust Rotating Pier Adapter (900RPA). Please note, a complete set is included with your pier adapter when you purchase it.
Mounts: All 900 mount models (HDA, QMD, SMD and GTO) that have been produced.
Back to topHeavy-Duty Azimuth Adjuster Upgrade Kit for 900 Mounts (9AZKIT)
one-piece assembly makes azimuth adjustment
easier and more accurate for precise polar alignment
in your observatory or in the field. The heavy-duty
construction and integrated one-piece design
results in smooth control of the azimuth axis.
Large left and right adjuster knobs are graduated
for precise control of azimuth position angle.
The small graduations are 1.3 arc minutes per
graduation; long graduations are 6.5 arc minutes
per graduation. The size of the knobs makes
them easy to turn with very little torque required,
even with the mount fully loaded.
The kit includes a set of hardened washers for the four lock-down knobs. With these washers, the lock-down knobs can hold the mount down tight, while still allowing the axis to be easily adjusted with your fingers. This will eliminate minor shifts in the axis when you are tweaking your azimuth adjustment.
The adjuster block installs
easily on your base plate using the existing
hole pattern and screws. Simply remove the two
existing adjuster blocks and replace them with
the new unit. Place the four washers beneath
the lock-down knobs. The washers have a sharp
edged side and a rounded edge side. Place them
with the sharp edge of the washers facing up
toward the knob, rounded edge down onto the
painted surface of the base plate. Complete
instructions and tips for adjusting both the
azimuth and altitude axes are included in the
package. Installation takes only a few minutes,
but will result in significantly easier setup
the next time you are out under the stars.
Back to top1.2" Azimuth Adjuster Block (M12020-A)
|If you purchase the Azimuth Adjuster
Assembly (S1200AA-A) and use the Standard Pier Adapter, you may wish to consider
upgrading to the new taller Azimuth Adjuster Block,
as well. Although the original 1.1" block will
work effectively with the new adjuster assembly,
this new 1.2" provides a better connection for
the opposing screws and looks proportionate. This
is a suggested, but not essential upgrade. This block is not needed if you use the Precision-Adjust Rotating Pier Adapter (900RPA) or if you are ordering a new Standard Pier Adapter (900SPA). |
Mounts: All 900 mount models (HDA,QMD, SMD and GTO) that have been produced.
|M12020-A||$15.00||NO LONGER AVAILABLE|
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Polar Fork Assembly (S900PF-A)
The height was increased to allow more
room for your hand when tightening the rear knob or adjusting the altitude.
We also eliminated the sharp corner to prevent the possibility of the
cords catching. It looks a bit spiffier as well.
Note: This Tall Polar Fork Assembly Upgrade is now included on all new 900GTO Mounts and does not need to be added to a new 900GTO purchase.
Mounts: All 900 mount models (HDA,
QMD, SMD and GTO) that have been produced. Plese note: HDA and QMD mounts require removal of the RA motor/gearbox to change out the polar fork.
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900 Altitude Adjuster Assembly (9ALKIT)
Individuals who own the very earliest 900 mounts may want to consider upgrading to this more substantial altitude assembly. You may also consider purchasing just the Altitude Adjustor Brace (9ALBKIT) described below if you want to reuse the original Altitude Knob, Threaded Rod and other components, which are common to both designs. Installation instructions.
Includes: Our part # S900AA-A, four 1/4-20
x 5/8" flathead socket cap screws.
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900 Altitude Adjuster Brace (9ALBKIT)
If you do not
wish to replace the entire Altitude Adjuster
Assembly with 9ALKIT above, you may wish to
consider purchasing just the brace and installing
the other original parts yourself. Installation
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900 R.A. Clutch Set Screws (F0021), recommend two
If you operate your mount remotely and are concerned about cables snagging on the RA clutch knobs, you may wish to remove them and substitute our modified set screws. Please do not attempt to install standard set screws, since they must be a particular length and profile to work properly. If you install the modified screws, you will have to use the 5/32" allen-head wrench from the set included with your mount to loosen and tighten them. Please tighten evenly with respect to the opposing clutch knob and do not over tighten. These set screws are only necessary for the side of the mount that has the cable. The normal clutch knobs will remain on the other side. Please note that each mount requires only 2 modified clutch set screws.
Mounts: All 900 mount models (DA, QMD, SMD and GTO) that have been produced.
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Replacement Assembly for 900/1200 Dovetail Knob (DOVEKBREP)
To reduce the possibility of a cable snag while operating your mount remotely, you may wish to remove one of the dovetail knobs that secure the Dec axis to the R.A. axis, and substitute it with our replacement assembly. The assembly would only be needed for the side of the mount that has the cable. The standard dovetail knob will remain on the other side. You will only need to purchase one per mount.
WARNING: Do not over-tighten the knob replacement assembly!
Note that a small portion of the assembly will protrude from the side of the mount. This is normal and should not interfere with the mount cable during remote operation.
Please refer to the image at the right.
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900GTO Name Plate (M12611E9G)
Engraving on the name plate
has been changed to "Astro-Physics 900GTO Servo
Drive". The original SMD
(servo motor drive, but not go-to) and GTO (servo
motor drive with go-to) versions of the mount
shared the same name plate "Astro-Physics 900
Servo Drive". Note that the GTO designation
was not there. We decided to more clearly identify
the mount and offer the new name plates to prior
GTO owners, as well. You will need two name
plates, one for either side of the Dec. axis.
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900GTO Quick Release Control Box Adapter Kit (9CBKIT)
If you are upgrading your
900GTO from the GTOCP1 Control Box, you will
need this adapter kit. It features a dovetail
attachment so that the GTOCP3 control box can
be easily removed. Simply loosen the two thumbscrews
and lift the control box from its position.
We also provide two set screws if you prefer
to use them.
Mounts: 900GTO only. We will request the serial number of your mount when you order to ensure that this adapter can be used with your mount.
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R.A. Sight Hole Cover - for 900GTO mounts shipped since October 2005 (M9403)
This sight hole cover threads onto the back of all 900GTO mounts shipped since October 2005. One of these aluminum covers is included with all new mount purchases, but now they are available separately for anyone who needs one.
The rear of the 900GTO R.A. axis was redesigned in October 2005 to be slightly larger than the 1200s, 400s and earlier versions of 900s. This change resulted in the need for a larger diameter cover.
|If you are uncertain when your 900GTO shipped, please use the photos (right) as a reference for where to measure on your mount to determine the correct cover size. We used a 1200GTO since it was readily available; however, the measurement points are identical on older 900 mounts.|
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900 Declination Axis Upgrade (900DU)
For all previous model 900 mounts, we can upgrade the bearing system in the Dec axis to the present standard. This will allow full tracking and guiding with excellent precision in all mount orientations including upside down operation well past the zenith. In addition, we will add a spring-loaded bracket, modify the worm bearing support for more precise worm reversals and check out all guiding functions with our test equipment. List of things we will install:
Should I upgrade my mount?: It is only when you are trying to control the mount to arc second position accuracies in declination that it becomes important to have this axis modified to the latest configuration. If you don't fit this profile, the upgrade is not necessary. This is a very expensive upgrade procedure and will only be done to mounts that exhibit a problem in the Declination Backlash Test.
Mounts: All 900 mounts with serial number 900450 and earlier numbers, as well as 900501. Mount models include 900HDA, 900QMD, 900SMD and 900GTO models. All mounts with later serial numbers were built with these upgrade features at the time of production.
Upgrade Schedule: June 26, 2015
Dec axis MUST ARRIVE between June 22-25, 2015
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Astro-Physics, Inc. - All Rights Reserved
This page was last modified: May 29, 2015
11250 Forest Hills Road, Machesney Park, IL 61115, U.S.A.
Phone: 815-282-1513 Fax: 815-282-9847