Mathis Instruments MI-500 User manual

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Setup Guide
MI-500, MI-750 & MI-1000
Fork Mounts
Mathis Instruments
www.mathis-instruments.com
January, 2016
MI-750/1000 Fork Mount

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Table of Contents
Introduction 5
Mount Components 7
Polar Base 7
Base Plate 8
Rocker and Rocker Base 8
Polar Cone 9
Equatorial Forks 11
Telescope Plates 12
Altazimuth Fork Mounts 13
Azimuth Base 14
Altazimuth Fork 14
Electronic Controls 15
Servo II 15
AstroPhysics GTO4 17
Installation 19
Uncrating the Mount 19
Hardware 19
Base Plate and Pier 19
Rocker Base 20
Fork Hub 20
Fork Arms 21
Installing the Telescope 22
Slip Clutch 24
Adjustments 27
Azimuth 27
Altitude 28
Balancing the Mount 29
Orthogonality of the Telescope 30
Polar Alignment Using Polaris 32
Polar Alignment by Star Drift 33

Maintenance 35
Lubrication 35
Cleaning 36
Worm Plate 36
PEC Sensor 38
Home Sensors 39
Renishaw Encoders 41
Cold Weather Operation 44
Electronic Damage 44
Technical Support 45

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Introduction
Congratulations, and thank you for purchasing your telescope mount from Mathis
Instruments. We are confident that the design and construction of our mounts
will serve you well in your astronomical pursuits. This manual will explain the
components, setup, operation, and maintenance of your equatorial or altazimuth
fork mount.
Each of our fork mounts is available in an equatorial or altazimuth configuara-
tion. Our family of mounts includes the following:
Model Application
MI-500 12-16 inch telescopes
MI-500 /750 14-18 inch telescopes 500 base with 750 fork
MI-750 16-20 inch telescopes
MI-750/1000 18-20 inch telescopes 750 base with 1000 fork
MI-1000 20-24 inch telescopes
MI-1000/1250 24 inch telescopes 1000 base with 1250 fork
Our mounts are also available in a German equatorial configuration. The
assembly and operation of fork and German mounts are very similar. In
most cases, the size and weight of these mounts make it very challeng-
ing to transport the equipment to a remote site, and in general, they are
designed to be permanently housed in an observatory setting. Only the
MI-500 is light enough to be transportable, provided you have sufficient
determination and strength. These instructions focus primarily on observatory
installations.

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Mount Components
Polar Base
Each equatorial fork mount has a polar base as one of the key components.
The polar base contains the right ascension axis, the worm gear drive, and the
servomotor that provides slewing and tracking to follow celestial objects across
the sky.
The polar base has the following parts: the base plate, the rocker base, the
rocker, the polar cone, the right ascension (RA) axis, the RA worm gear and worm,
motor assembly, and the gear casing with removable covers. The diagram below
illustrates these parts of the polar base.

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Base Plate for MI-750 Mount
Base Plate
The base plate attaches to the top
of your observatory column or pier.
There are different ways to do this,
but the most common is to put bolts
through the base plate that screw
into holes on top of your pier.
Alternately, the bolts can pass
through the base and the pier with
nuts threaded on to the end of the
bolts.
In most cases, we customize the
holes in the base plate to match the holes in the pier. Make sure that the base
plate is securely fastened to the top of your pier, since it is the foundation of the
mount and telescope.
The base plate and rocker base for the MI-500 and MI-750 mounts are round,
whereas the MI-1000 mount has a rectangular base plate and rocker base.
Rocker and Rocker Base
The base plate has a small push block on the north side. For the southern
hemisphere, this block is on the
south side. The rocker base is bolted
to the base plate and fits over this
push block. There are two recessed
set screws that push against this
block. During polar alignment,
these set screws are used to adjust
the azimuth angle of mount. One
can adjust the azimuth by about 4
degrees to either side of center.
The rocker is attached to the
bottom of the polar cone It has a machined curve that exactly matches the
concave curve in the rocker base. The polar cone and rocker sit on top
of the rocker base and are secured by four stainless steel bolts.
These four bolts pass through the slotted holes on the sides of the rocker and
screw into threaded holes in the rocker base. The rocker is bolted to the under-
side of the polar cone at the factory and should never need to be removed.
Azimuth Adjustment Screw in Rocker Base

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On the back side of the rocker base
there is an altitude adjustment
screw. This screw is used to push
against the bottom of rocker. This
will change the altitude of the polar
assembly to match the latitude of
your observatory.
When you place the rocker and
polar cone on to the rocker base, first
apply a small amount of grease
on the convex and concave mating
surfaces. This grease will allow the
rocker to slide easily on the rocker
base and will facilitate making
changes in the altitude during polar
alignment.
With the polar cone and rocker
bolted to the rocker base, the entire
weight of the telescope and mount is
supported across concave surface of
the rocker base.
The rocker-base of the MI-500 and
MI-750 mounts has the azimuth adjustment screws on the north side of the base.
The MI-1000 mount also has azimuth adjustment screws on the north side of
the rectangular rocker base, with the altitude adjustment is on the south end.
Polar Cone
On the front of the polar cone is the gear casing. This casing encloses the right
ascension worm gear, the worm, the motor assembly, and the casing covers. The
casing itself is rigidly fixed to the polar cone and should never need to be re-
moved. It provides the mounting surface for the worm assembly and servomotor.
The gear casing cover consists of two parts. The circular cover at the top of the
casing provides protection for the worm gear and should be left in place except
when cleaning is needed. The lower area of the casing is covered by a smaller
trapezoidal plate that can be removed whenever lubrication or when adjustment
of the worm and motor assembly is needed. You can easily remove this cover to
inspect the servomotor and drive gear.
Rocker and Rocker Base for MI-1000
Altitude Screw in Rocker Base

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The polar axis of the mount pass-
es through the polar cone. It is
supported by a large shielded bear-
ing at the top of the cone and a
smaller guide bearing at the bottom
of the cone. A black anodized nut is
threaded onto the end of the polar
axis and serves to provide a modest
thrust load to the bearing assembly .
The top surface of the polar axis is
where the fork assembly is attached.
For German mounts, the declination
assembly bolts to the top of polar
axis.
The picture at the right shows the
inside of the gear casing with
the worm gear, worm plate, and
servomotor. Depending on the
electronic control, the motor shaft
drives the worm shaft using pulleys
and a timing belt. For other mounts,
the motor drives the worm shaft
using a set of spur gear reductions.
Polar Cone on Rocker Base
Right Ascension Worm Drive