Interface Control Document Cassegrain Instruments For The Palomar

interface control document -------------------------- cassegrain instruments for the palomar 200-inch telescope ------------------------

Interface Control Document
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Cassegrain Instruments for the Palomar 200-inch Telescope
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version 1.0
November 2, 2010
A-109488
Table of Contents
1.
Introduction and Reference Drawings
2.
Optical Interface
3.
Mechanical Interface
4.
Electrical Power Interface
5.
Data Interface
6.
Handling and Storage
7.
Dimensions
8.
Defining points
1.0 INTRODUCTION and REFERENCE DRAWINGS
1.
Purpose
The purpose of this document to provide pertinent information for
potential designers of new instruments for the Cassegrain focus of the
200-inch telescope at Palomar.
Most of that information is on several drawings in the Palomar files.
These drawings numbers and titles will be listed next for reference.
However, extracts from those drawings will be made later in this
document so that the designer will have immediate access to much of
the vital information needed about the Cassegrain focus area.
1.2 Reference Drawings
Drawing No. Title
B-104954 Sheet 1 - 200” Telescope, Cassegrain Optical Sys.
B-104954 Sheet 2- 200” Telescope, Cassegrain Optical Sys.
B-104954 Sheet 3- 200” Telescope, Cassegrain Optical Sys.
B-104954 Sheet 4- 200” Telescope, Cassegrain Optical Sys.
B-105361 200” Cass. Offset Guider Opt. Layout
B-105372 200” Cass. Offset Guider Mtg. Frame
B-108332-1 200” Cass. Guider Base Plate Blank
B-108332-6 200” Cass. Instrument Mounting Pin
D-108342 200” Cass. Guider Handling Fixture Assy
D-108343 200” Cass. Guider Handling Fixture Parts
112631 200” Cass Instrument Envelope drawing
2.
Optical Interface
Drawings 1.3 through 1.6 describe the Cassegrain Optical System in
some detail. Sheet 1 of B-104954 was made in 1962 and is the most
complete, but there are some errors. In 1997 Sheet 2 was made to
correct the problems and provide only essential information about the
optical system using the best available figures.
Based partly on reference drawing B-105361, B-104954 Sheet 2 shows a
typical Cassegrain focus at F 15.78 with a light beam that is 13
inches in diameter and with a 14 arc-second field. The beam in the
instrument is typically 1-inch in diameter. The focal surface in the
example is at a typical 9.12 inches below the surface of the
Cassegrain rotating mounting ring.
Focal position adjustment is made by shifting the Cassegrain secondary
mirror through about 2.8 inches (70 mm) of travel and that provides a
Cassegrain focal range of about 30-inches each way from the
above-mentioned 9.12 inch position. There the plate scale is 2.56
arc-seconds per millimeter (at F 15.78).
B-104954 Sheet 3 shows the equations that pertain to a Cassegrain
optical system and shows a dual optical layout. The purpose of the
latter is to show what happens as one shifts from one focal position
to another. The two points shown are at distances Co and C1 behind the
front surface of the primary mirror.
B-104954 Sheet 4 is really a worksheet that shows how to use Sheets 2
and 3 to make useful calculations.
For example, the focal location for F 16 was calculated and shown on
Sheet 2. It was 11.07 inches below the F 15.78 position.
2.
Mechanical Interface
3.1 A typical Cassegrain instrument for the Palomar 200-inch telescope
is supported by a large rectangular 2-inch thick steel base plate
about 34.5 by 45.5 inches overall. Near the corners are four 1-inch
diameter through holes on a 32 by 42.875 inch hole pattern. In each of
these four holes are mounting pins (drawing B-108332-6). Drawing
B-108332-1 shows a base plate blank and some partial assembly views of
the pins in the plate and a section view of one pin secured to the
Cassegrain rotatable mounting ring. Of course, all four pins will be
locked in place in service. Naturally the base plate will also have
various through holes and tapped holes to accommodate the optical and
other components of the instrument.
Drawing B-105372 was referenced as an example of an earlier instrument
that is shown attached to the Cassegrain mounting ring. In that case
the base plate was of cast iron. Many Cassegrain instruments may weigh
a ton or more and to minimize re-balancing effort of the telescope
tube it is desirable that new Cassegrain instruments are heavy too. A
thick and heavy base plate helps that and provides rigidity also.
2.
Electrical Power Interface
Standard 120 volt, single phase 60 Hz power is available in a duplex
outlet near the instrument area and also in electrical cabinets that
are available to house users electronic equipment.
5.0 Data Interface
Various data cables used by other instruments are available. At
present we do not have an up to date list of the details of these.
6.
Handling and Storage
A Cassegrain instrument must have its own handling fixture (often
called a cart) for transport to and from a storage shed located around
the periphery of the 200-inch telescope’s observing floor. An example
of such a cart is shown on drawings D-108342 and D-108343. That cart
has a rectangular base frame that is 52 inches square and is mounted
on four
heavy-duty casters of 5-inch diameter. The overall height is 84 inches
to the tops of the four 9/16 inch diameter pins that engage the
instrument base plate’s four holes on a 32 by 36 inch pattern.
Each pin is on top of a plunger assembly that slides inside a 2-1/2
diameter tubular post on the cart. Each plunger has a strong spring
and an automobile type shock absorber incorporated in it to cushion
any inadvertent bumps as the Cassegrain instrument is attached or
detached from the rotating mounting ring locking device. The vertical
motion to raise and lower the cart is provided by a 5,000 pound rated
central hoist platform directly under the Cassegrain area when the
telescope tube is vertical.
6.
Dimensions
The above-mentioned Cassegrain cart will accept an instrument of about
26 by 32 inches in cross-section at the four posts. However,
additional space is available between the posts if needed. The
instrument body may extend about 62 inches below the bottom of the
instrument base plate. Above the base plate there is a space of 38
inches up into the mirror cell and the primary mirror but limited to
32 inches in diameter. However, that space should be verified to be
available before an instrument is designed to use it.
8.0 Defining Points
The final defining points are the flat ends of the four mounting pins
against the gear plate (drawing 103783) to which the Cassegrain
rotating ring is attached. There are tapered clearance holes in the
mounting ring to guide the pins through to contact the gear plate.
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