Highland Road Park Observatory
Specifications for the Observatory Telescope & Mount
- Ritchey-Chretien 20" f/8.1 Telescope
using hyperbolic figured 20" primary and 7.25"
secondary lightweight conical shaped low expansion
- The mirrors will be aluminized and covered
with a protective coating that meets or exceeds milspec
MIL-M-13508C for resistance to abrasion and corrosion.
- The reflectance (for a single reflection)
will be as flat as possible in the wavelength range from
400 nm to 750 nm, with a maximum value of at least 95%
and a minimum of no less than 90%. From 750 nm to 1000 nm
the reflectance should be no less than 80%.
- The optical system will be diffraction
limited, having a final wave front error of 1/4 PV and
- A Zygo interferogram with fringe analysis
will be provided to certify the optical quality of the
- The mirrors will be mounted in a closed
painted 6061T-6 aluminum tube with anodized aluminum
components and stainless steel fasteners to resist
corrosion and minimize infrared scatter.
- A sealing mirror cover will be provided.
- Both mirrors will be held rigidly while
allowing for differential coefficients of expansion
between the mirror and mount.
- Optical collimation adjustment screws are
widely spaced, providing fine adjustment and secure
- A electronic, stepper motor controlled
secondary focuser will be provided and designed so that
the focus is stable during a change in instrument
- Boresight stability will be ± 20
arcseconds regardless of telescope orientation.
- The telescope assembly will be equipped
with slewing handles.
- Threaded holes, will be provided on the
back plate,for instrumentation attachment.
- Full length counter-weights on both sides
will facilitate symmetrical, fine balancing of the
- Included with the scope will be a 11 X 80
illuminated finder telescope with a Polaris reticule, a
tube attachment fixture, clamping rings, a 2" star
diagonal and a 55mm Tele Vue eyepiece.
OGS140 Equatorial Fork Mount:
- Equatorial fork mount for telescope to be
constructed of precision machined aluminum and stainless
steel alloys with axles of 6" O.D..
- The axes of the mount will be orthogonal
to better than one arc minute.
- The mount will have an equipment capacity
of at least 290 pounds.
- The clearance between the telescope
backplate and the fork top surface will accommodate a
swing-through of at least 18 inches.
- Both axle drives will include Byers gears
with a 18" gear on the Right Ascension axis, slip
clutches, negligible backlash between the worm and worm
wheel, ABEC7 pre-loaded ball bearings to support the worm
shaft, and a beam coupling to connect the drive motor to
the worm drive providing anti-backlash, constant velocity
power transmission and vibration damping.
- The telescope optical axes will be aligned
with the mount axes to within 1 arcminute and the
combined system will be capable of tracking objects with
an accuracy of less than 3 arc second periodic error
without the need for computer correction.
- The mount will be set for a latitude of 30
degrees, 23 minutes and include fine adjustment for
azimuth and elevation.
Computer Control System:
- The computer controlled telescope system
consists of software capable of providing telescope
focusing, slewing, tracking, and dome control as well as
the electronic interface to the telescope, mount and
- A Pentium computer with monitor, keyboard
and mouse, compatible with the software and electronics,
will be supplied to provide the direct user interface as
well as the interface to a remote control system.
- All motors, sensors, cabling and
interfaces will be provided and the system will be
compatible with an existing Ash Dome (model 22.5' MEBH).
- The slewing motor speed will be adjustable
so that the telescope can be quickly positioned and then
accurately centered on an object.
- The tracking motor speed will be
adjustable and provide sidereal, lunar, solar, cometary,
asteroidal and user definable tracking rates.
- A control paddle will control the speed
(guide, drift, slew) on the drives and direction (all
cardinal directions) of the telescope motion independent
of the computer keyboard.
- The system will be capable of compensating
for an object's proper motions, the effects of
precession, nutation, annual aberration, atmospheric
refraction and parallax as well as for
mechanical/optical/polar misalignment and periodic error.
- This compensation enables the telescope to
be positioned on any object in the full sky to within ±
30 arcseconds RMS and to track the object over 20 minutes
of time to less than 1 arcsecond of error.
- Dome control includes dome rotation and
shutter open / close operations along with manual
- A "rain sensor" signal will be
supplied by LSU and will be used in the software to veto
the shutter open operation and to automatically close the
shutter during remote operations.
- Finally, all control functions, readouts
and displays, with the exception of configuration and
calibration operations, should be accessible over a T1
internet link and should be capable of using software
such as TheSky as the user interface.
Last updated by Frederick J. Barnett on Thursday, January 20, 2005 11:48:09 AM