Optical | Mechanical |
Control System| Other
specifications and features
Updated January, 2005
1999 prototype image
Primary Mirror 18.2" nominal diameter. Molded
/generated light weight tapering Pyrex for rapid cool-down. Weight
~ 40 pounds. Hyperbolic asphere yielding a 50" focal length
in conjunction with field corrector lens group. Null figured
to 1/4 wave or better. Aluminized and 1/4 wave silicon monoxide
overcoated. A central target for laser alignment is permanently
etched on surface. The mirror /rear cell is attached to the trunion
box by 4 nuts and can be removed without affecting collimation
and then placed in supplied hinging anti-static padded carrying
Field corrector lens group is designed with moderately
curved surfaces to minimize multiple reflections from brighter
stars and is magnesium fluoride AR coated on all surfaces. It
is sized to illuminate a 35mm format to corners with negligible
vignetting. The optical design is balanced to optimize the central
20mm for CCD performance and still deliver ideal 35mm film imagery.
Back focus distance from lens cell to focal plane is a maximum
of 60mm OPD. Optional enlarged rotatable T-ring adapters can
interface 35mm SLRs.
Optical Tube Assembly is a combination of formed steel (trunion
box and spider vanes), aluminum castings and milled bar, and
carbon graphite truss tubes. Metal parts are either black anodized
or non-glare texture powder coat painted (baked on) all surfaces.
Most fasteners are stainless steel. Removable light shrouds at
primary and prime focus are painted with low reflection textured
powder coat. Full collimation adjustments are accessible.
Main trunion box assembly, less
primary mirror and its 3 point collimation fasteners.
Focusing is via tiny DC gear motor with absolute
position numeric LCD display
on a remote hand box that is battery operated with auto-off feature.
A standard cable length of 10 feet is supplied and extensions
to add another 50 feet are available. Focus is achieved by moving
the corrective lens group inside the spider hub casting via a
backlash free drive screw. Focus is positive and repeatable.
The CCD camera is rigidly affixed to the spider hub casting.
Central obscuration The prime focus baffle has a nominal
O.D. which is 4.5" or ~ 6% by area in relation to the primary
mirror diameter. The truss tubes are outside the entrance pupil and do not interfere. Spider
vanes are stamped thin steel. With the ST-237 imager, the focus
baffle diameter is still the limiting obscuration size. With
the ST-8/10/2k imagers there is a nominal increase to ~5"
diameter (7.7%) obscuration with a slight offset (see Q&A
mm SLR attached at prime focus
Fork: CNC stamped, formed and TIG welded steel.
Two pairs of opposing tapered roller bearings are preloaded for
thrust and radial control of central trunion box. Declination
axles are precision centerless ground and threaded stainless
steel. Fork has a massive 6" x 12" cross-section at
its base, tapering continuously up toward the dec shaft bearing
housings. Internal ribs and
shear plates as well as true one piece construction make
this assembly extremely stiff, yet light. The fork and trunion
box have through holes to allow for use of the included polar
alignment scope even while the entire telescope is operational.
The fork and polar base are designed to follow the now
popular Stealthlike angular aesthetics.
Two massive tapered roller
bearings, separated by ~18", support the precision centerless
ground and threaded hollow steel axle.
Rear threads allow attachment of the illuminated reticle pattern
polar alignment scope. The fork is coupled through a massive
drive disk casting (anodized) which has minimal overhang and
a near zero torque moment distance. Six each 3/4" stainless
steel bolts couple the fork to the drive flange.
prior to welding
The main structure is welded
tubing sized for minimal weight with maximum rigidity. The base
has adjustable side mount feet bolted to the user's latitude
range and has leveling bolts and through
holes for hold down. The entire telescope is designed to balance
on a flat surface before being bolted down. Steel side panels
enclose the base to offer a pyramidal form. All structural parts
are 100% powder coat painted (baked on) excepting non-exposed
critical machined surfaces.
The polar axle roller release operates by turning
the black lever.
of the anodized cast aluminum drive disks are directly driven
independent of any possible torque flexure from their supporting
axles. This allows for precise response and maximum rigidity.
The declination drive roller is a hardened and precision ground
stainless steel output shaft. originating directly from the
custom made planetary gear reducer / stepper motor drive
modules. This drive module contains 6 roller and 5 ball bearing
units which result in a powerful high speed, quiet slew that
is energy efficient with minimal backlash. The RA drive is a
new worm reducer type roller drive(2004 and later). These
are hand lapped for near zero backlash performance.
Lightened Dec drive disk casting
dec drive module has a quick release tension mechanism
to allow for precise balancing of payloads and also safe
transporting. A preset slippage tension helps to minimize any
accidental slew-to damage. Heavy gauge spun aluminum covers
protect the drive disks.
A simple one half turn of
the arrowed lever will disengage the declination roller for exact
Squareness of the declination
axis to the polar axis
is set to + 15 arc seconds or better.
Squareness of optical axis
to the declination axis
is set to 40 arc seconds or better. Note that this is also subject
to primary mirror collimation adjustment in the field.
Typical opto-mechanical system
flexure over a 120 degree declination motion is ~ 60 arc
seconds per T- Point modeling corrections.
Mechanical: A closed loop design utilizing encoder
feedback was found to be the most reliable and also allows for
manual positioning. It would be simpler to just count motor steps
(which our system also allows), however the gear coupled high
resolution encoders deliver a 1 arc minute pointing position
with little error and can easily follow counts at the maximum
slew rate. With such a design, there is no need to re-sync
if a clutch or drive slips, a stepper burps, or if you simply
desire to grab and point the telescope toward an object. The
stepper motors are specially designed to run in a very efficient/accurate
micro-step mode. Sidereal tracking step sizes are less than 1/10
arc sec. Both axes encoder drive modules are enclosed in stamped
aluminum boxes for protection.
user friendly hand control is compact at 2 1/2 x 4 inches and
has just 5 buttons and a 2 line variable brightness red LED display.
The default display parameter shows the current position coordinates
displayed as RA: hour - minute - .1 minute on top line,
and DEC: degrees - minutes on next line. A 5 or 10 meter
cord with connector at one end attaches to the micro-processor
controller. The other cable connector positions at the controller
chassis are for motors and encoders, autoguider input (6 pin
modular and 15 pin SUB D), serial communication to optional host
computer, and 12 VDC input (banana jack). A size matched 13.8
VDC regulated power supply with 110 VAC input is physically joined
and electrically attached to the controller chassis by a plug
set. The controller draws about 3 amps maximum @ 12 volts and
is contained in a heat fin cooled chassis of ~4x6x2 inches.
Functional: There are
5 available speed slots that can accept any chosen speed between
.05X to 1600X sidereal. Settings of .5X-2X-20X-100X-900X (~4
deg/sec. slew-to) are preset and easy to change as desired.
.5X in the first slot is the maximum speed in autoguiding/selfguide
modes, while the last slot establishes the fast slew-to
speed. No software or computers are required for stand alone
operation of the Centurion. All firmware is in EPROM which is
easily upgradable as new firmware features appear.
Firmware features: Lunar, solar, sidereal, and non-tracking
rates - 2 axis programmable drift correction for comet tracking-
spiral search- push-button logic flips- timer- red light- English/German
language- de/acceleration ramps- 2 axis variable backlash- fine
tracking speed adjust- internal library look-up/scroll-to/GOTO-
one star initialization- fool proof guest mode lockout-
24 hour-on energy saving mode that preserves nightly syncronization-
direct RA-DEC input, southern hemisphere operation, etc. The
stand alone memory has about 4000 objects such as Messier, NGC,
IC, stars, solar system objects.
Optional: Once interfaced to The Sky etc.
through the user"s PC, the object library number can dramatically
increase by 5000 fold. That interface is seamless and
as simple as plugging in a serial cord (included). It is also
useful for operating the Centurion at distances greater than
the hand control cord allows. The Sky presents a scope
pad interface which serves as a second hand control box.
The Centurion hand control still works in parallel when The
Sky is interfaced and synched, e.g. the scope can be moved
by either control and also by hand without losing sync. The computer
interface emulates most of the standard LX protocol. When using
The Sky on a remote computer from distances further than
4 meters, it may be necessary to also extend cables for CCD control
and the electric focuser. 50 feet is the current limit for hard
wire operation. Beyond that a network connection with two PCs
An optional 24 volt power supply
and control module will allow higher torque for up to 1400X
slewing speeds and is listed on the price list.
OTHER SPECIFICATIONS AND FEATURES
The main mirror cover is spun
aluminum, powder coat painted and can protect the primary mirror
when not in use. Rear light shrouds allow for air flow around
the primary (removable for in-place mirror cleaning). The
DEC and RA drive modules are enclosed. A precision 2" I.D.
focus coupler with mating 1 1/4" reducer allow for simple
visual and basic CCD coupling. Exact focus spacing information
is supplied for optimal performance. One set of screw-on counterpoise
weights are supplied for precise balancing in the declination
and RA axes. The standard finder scope is a 9x50mm straight thru
type. This can be placed as desired on the trunion box. Manuals
covering setup, operation and the control system are included.
Support via phone and fax is included. The fully assembled Centurion
is palletized for motor freight shipment, with primary mirror
in its own padded container and computer control system packed
separately. Total telescope weight is approximately 350 lbs.
(less crate). The complete telescope fits in an envelope of ~56"
high by 46" wide by 72" long @ a 36 degree latitude.
Northern latitudes will add to the height dimension. If you want
even more information about the Centurion 18, please refer to
Questions and Answers for additional
New features: The Latest series Centurions have many improvements described within
Guarantee: Every telescope is set up and 100% functionally
operated and CCD performance is verified with actual images.
Each telescope will be capable of delivering images equal to
or better than any displayed on our website. User sky quality
and technique will vary, so some results may be better while
some worse. As new CCD cameras become available, some may work
very well with the Centurion and others may not. We rely upon
the reputations of our optical fabricators to maintain high quality
standards. Our opticians stand behind their respective work as
do we with regards to fabrication and integration of the entire
system that makes up the Centurion 18. Our tires meet the pavement
with 100% performance testing of every unit for optimal
results. This is our guarantee. The drive electronics are warranted
for one year from date of purchase excepting acts of nature (rain,
electrical storm, snow) and abuse (using a battery charger to
power scope, etc.).
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