Specifications

4
SECTION 2.0
THEORY OF OPERATION
2.1 BASIC PHYSICAL CHARACTERISTICS
The Pyxis camera field rotator is comprised of a fixed circular plate that is attached to the
telescope’s focusing mount and a rotating plate that is attached to the CCD camera or other
imaging device. A stepper motor with drive gear rotates the plate attached to the CCD through
360 degrees in 1 degree steps when used to find position angle. The total gear reduction is 110 :
1. Combined with the 48 steps per revolution of the stepper motor drive shaft, one complete
revolution of the camera takes a total of 5280 steps. Thus, each step from the motor rotates the
main drive gear holding the camera by about 4 arc minutes.
The Pyxis 3-inch is similar in concept but uses a large 6-inch diameter bronze worm gear and
stainless steel worm. The 360 tooth worm gear is cut “double start” which makes the effective
number of teeth equal to 180. An 9 tooth spur gear on the motor shaft drives a 48 tooth gear on
the worm shaft. This results in a total gear reduction to complete one revolution taking 46080
steps. Each step is thus equal to 0.469 arc minutes.
Only two cables are required to operate the Pyxis or Pyxis 3-inch. The first one is a low voltage
12 VDC cable with 2.5 mm power plug to supply operating power and the other is a 6-conductor
RJ-12 cable for connection to a PC or laptop computer. The Pyxis needs a computer for proper
operation and cannot be operated in a stand-alone mode.
The Pyxis with T-mount and telescope adapter weighs 27 ounces. The approximate dimensions
of the unit without adapters are 6-inches in diameter and 1.5-inch thick. See Figure 2-1 for an
assembly and cross sectional view of the Pyxis.
The Pyxis 3-inch uses the same adapters as the TCF-S3 for connecting to the telescope or to the
camera. This model is not compatible with any of the camera side adapters used for the smaller
Pyxis. The approximate dimensions of the unit without any adapters is 6.4 X 7.5 X 2.4 inches and
weighs 4.5 pounds. See Figure 2-1a