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MI-500F EQUATORIAL FORK
The MI-500 mount is available in a German equatorial and an equatorial fork configuration. The MI polar cone and base are identical in either configuration. The polar cone houses the right ascension axis with drive gear and DC servo motor. The polar base supports the cone, and includes azimuth and altitude controls for polar alignment.
For a German mount, the declination assembly attaches to the top of the right ascension axis. For a fork mount, the fork arms and central hub attach to the top of the right ascension axis. A single mount can, in fact, be converted from a "fork to German" or "German to fork" configuration by adding the appropriate declination assembly.
The MI family of telescope mounts include the following major features:
Main components with a distinctive geometry that combines style, strength, and function.
Large aluminum castings that provide the outer structure of the mount.
Telescope axes machined from alloy aluminum bar-stock and black anodized for durability.
Shielded ball bearings that are fitted into the machined castings and support the telescope axes.
Large worm drive gear on each axis with matching worm in a precision bearing housing.
Spur gears or belt drive on each axis that connect the motor shaft to the worm shaft..
Computer controlled DC servo motors with mounting brackets.
Cover plates that shield the drive gears and servo motors.
The aluminum castings in each mount are molded using accurate patterns and cores that produce parts of consistent quality. The various machined components are made on computer controlled machines as well as precision manual machine tools. In particular, the worm assemblies are hand crafted, where consistent accuracy of .0001 inches (2.5 microns) is needed.
The telescope axes, flange plates, and hubs are all machined from alloy aluminum barstock. The declination countershaft is threaded stainless steel, and all fasteners are stainless steel. All motors and drive gears are enclosed in protected casings. No brackets or gear boxes protrude form the mount, and all electronic components are enclosed.
The finished mount has a conservative, handsome look with the black anodized aluminum parts contrasting with the durable "blue-white" painted castings. The conical style of the mount features minimal hardware with only essential adjustment bolts visible. The final product is a precision platform for CCD imaging, conventional photography, and visual observation.
The equatorial fork configuration consists of a pair of tapered fork arms and a central hub. The thick-walled arms are castings made of #319 aluminum with a tapered box design. Each fork arm is machined on a computer controlled milling machine, assuring perpendicularity of the machined surfaces and uniformity in each set of fork arms. The declination axis of the assembled fork is perpendicular to the right ascension axis with an accuracy of 1 arc minute of angle or better.
Since the arms are detachable from the fork hub, the fork arm separation can be machined to the customer's required dimensions. The fork arms are bolted to the fork central hub using stainless steel hardware. Mechanical contact on two surfaces assures alignment and rigidity of the fork arms. The central hub with the attached fork arms is bolted to the top face of the polar axis.
A pair of pre-loaded bearings in each arm supports each flange plate. The telescope tube attaches to these plates. Interfacing a particular telescope tube to the fork requires customer-supplied dimensions, and in most case some custom machining will be required
One fork arm (usually the east arm) includes the declination gear housing with a fine pitch worm gear, a worm bearing housing, and a DC servomotor. A slip clutch allows one to balance the tube assembly and make fine adjustment whenever auxiliary equipment is added to the telescope tube assembly
The load capacity of each mount as approximately equal to the weight of the supporting polar cone and declination assembly. The MI mounts are not designed as portable equipment, so we do not minimize weight to achieve portability. While there are excellent mounts available that are quite portable, the load capacity of any mount increases when you increase the metal cross-sections and thickness of the supporting base.
The cast components of the MI mounts are generally heavy. They are designed primarily for installation at a fixed location. The MI-500 can handle 100-200 pounds (45-90 Kg).
In practice, each MI mount can actually handle a telescope weighing at least double the stated capacity. However, the mount flexure would be large, the clutches would be inclined to slip, the drive motors would be over-loaded, and the stability of the instrument would be compromised.
A mount is normally attached to a steel, aluminum, or cement pier. The pier can be fabricated, a thick-walled pipe, or other rigid material. Each mount includes a base plate to which the polar and declination assemblies (German or fork) are attached.
- Polar base that attaches to the top of the observatory pier or column.
- Polar cone with drive gear system.
- Fork assembly with drive gear system
- Necessary stainless steel hardware for assembly
- Electronic controls
- Servo II control supplied as standard equipment
AsroPhysics GTO3 or Software Bisque TCS available as an option
- User's Guide
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