TECHNICAL MANUAL FOR THEORY OF OPERATION AND OPERATING PROCEDURES INCLUDES THE NEW PYXIS 3-INCH OPTEC, Inc. OPTICAL AND ELECTRONIC PRODUCTS sales@optecinc.com http://www.optecinc.com 199 Smith St. Lowell, MI 49331 U.S.A.
Figure 1-1. Prototype Pyxis system mounted on a TCF-S focuser with SBIG ST-9 Camera.
TABLE OF CONTENTS November 2006 Section 1.0 2.0 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.1 . . . . .Basic Physical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 .Basic Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 .Position Angle . . . . .
LIST OF FIGURES Figure 1-1 Page Cover 1-2 Pyxis system mounted TCF-S focuser with SBIG camera . . . . . . . . . . . . . .Pyxis System Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2a .Pyxis 3-inch Camera Side View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2-1 6 2-1a Pyxis Field Rotator Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Pyxis 3-inch Rotator Assembly . . . . . . . . . . . . . . . . . . . .
SECTION 1.0 INTRODUCTION The rapid expansion of robotic telescope and observatories has created a need for many devices that enhance the operation of these facilities with regards to remote and unattended operation. In recent years, robotic telescope mounts, PC controlled focusers, filter wheels, dome controls, CCD camera with elaborate scripting functions and internet access has made possible, to the small observatory, sophisticated automated functions at low cost.
Figure 1-2. Pyxis System Components.
Figure 1-2a. Pyxis 3-inch Camera Side View.
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.
2.2 BASIC OPERATION When first activated, the Pyxis or Pyxis 3-inch rotates HOME to find the 180 degree position angle point which is detected with a magnet mounted in the rotating main drive gear and a Hall effect sensor mounted in the circuit board. Once the magnet is found, the unit reverses direction and rotates to the 0 degree position angle. The Pyxis will not accept any commands until the 0 degree position angle is obtained.
Figure 2-1. Pyxis Field Rotator Assembly.
Figure 2-1a. Pyxis 3-inch Field Rotator Assembly.
2.3 POSITION ANGLE The common way to measure position angle in the sky is to start at north at 0 degrees and rotate clockwise (abbreviated CW) through East (90 degrees PA), South (180 degrees PA), West (270 degrees PA) and back to North for a full 360 degrees. When using a telescope, the apparent rotation of the camera may be opposite when compared to the rotational direction in the sky. For this reason, it may be necessary to reverse the default direction.
The Pyxis control program makes the necessary calculations for obtaining the rotational rate and sends the appropriate codes to the Pyxis. The actual calculations are extensive and are not presented in this manual. For the programmer interested in correcting field rotation, see the CXxxnn command described in Table 4-9. Figure 2-2. Pyxis Camera Field Rotator T-thread Side.
SECTION 3.0 INSTALLATION & OPERATING PROCEDURE 3.1 INSTALLATION OF PYXIS The Pyxis rotator is shipped with a detachable 2” nosepiece. Power is provided by a 12 VDC switching power supply that can accept 110VAC to 230 VAC input. A 6-wire Reverse cable and serial port converter connect the Pyxis to the user’s PC for computer control of the rotator. Camera adapters need to be purchased separately.
3.2 INSTALLATION OF PYXIS 3-INCH To attach the Pyxis 3-inch to the telescope, one of the TELESCOPE MOUNTS for TCF-S3 or Pyxis 3-inch is needed. The most current selection is listed in the Optec price list. At this time, mounts are available for: 17801 17802 17803 17808 17809 Meade Telescope for 4” Rear Cell Thread - LX200 16” telescope Meade Telescope for 3” Read Cell Thread – most mid size telescope Celestron Telescope for 3” Rear Cell Thread -11” and larger sizes. AstroPhysics 2.7” mount Takahashi 2.
SECTION 4.0 PC SERIAL INTERFACE AND COMMANDS 4.1 PC (RS-232) SERIAL COMMUNICATIONS The Pyxis system provides a serial communications feature as standard. Using simple ASCII commands, both modules can be programmed with certain variables that are stored in the microcontroller EEPROM. The RS-232 interface operates at 19.2 K baud with 8 data bits, one stop bit and no parity. Optec has developed a user interface program called Pyxis.
4.3 COMMUNICATIONS PROTOCOL The remote PC communication program should be set for 19.2 K baud rate with 8 data bits, 1 stop bit, and no parity (8N1). The Pyxis is preset for these values and will not respond to other settings and cannot be changed. Tables 4-1 through 4-7 below describe in detail the commands used to control and communicate with the Pyxis. To establish communications with the Pyxis, plug in the power supply and wait for the Pyxis to complete the homing routine.
Command Return CDnxxx (no return characters) Function: This command sets the default direction either CW or CCW for proper rotation with regards to position angle in the sky. Enter 0 for n to rotate in the default direction or 1 to rotate in the reverse direction. The star fields of Refractor and Newtonian telescopes are mirrored with respect to each other. Match your sky atlas and camera control program position angle to the Pyxis. The value is stored in the Pyxis EEPROM. Trouble Shooting: Table 4-3.
Command Return CPAn1n2n3 ! (for every step made) F (when motion is complete) Function: The new position angle is entered as nnn for any integer value from 000 to 359. Note that left justified zeros are necessary for the entry. For example: to move to 10 degrees PA, enter CPA010. Trouble Shooting: An error code 3 is returned if the position angle entered is over 359. If the entered position angle is equal to the current, and error code 2 is returned. Table 4-6. Command to rotate to a new position angle.
Command Return CXxxn1n2 “!” Function: This command will rotate the Pyxis in the direction specified by n1 by n2 number of steps. n2 can be any value from 1 to 9 and n1 can be either a 0 or a 1. Position angle information is not updated when this command is used Trouble Shooting: If this command is used, the value for the current position angle will be in error. The Pyxis will have to be homed in order for the position angle to be found again. Table 4-9. Command to rotate by small steps.
4.4 PYXIS CONTROL PROGRAM Included with the Optec CDROM distribution software is a control program that will operate the Pyxis and allow for the controlling variables to be changed. The latest version of the control program can be found on the Optec website at www.optecinc.com. Look for the Software Download page in the Pyxis section. This program is self-extracting and will install all needed components when the file is opened.
SECTION 5.0 TROUBLE-SHOOTING GUIDE Contact Optec technical support for trouble-shooting any problems with the Pyxis camera field rotator. 1) A serial connection to the Pyxis with a USB-to-Serial converter can sometimes be frustrating. We have found that those converters using the FDIC chip set are the most compatible. The Pyxis.exe control software will not work with converters using the Prolific chipset. However, 3rd party software may be compatible with the Prolific chipset.
SECTION 6.0 SPECIFICATIONS for Pyxis MECHANICAL Main Gear Diameter Total Gear Reduction Number of Steps for One Rotation Degrees for One Step Load capacity 4.125 inches 110 : 1 5280 0.0682º (4.
SPECIFICATIONS for Pyxis 3-inch MECHANICAL Main Gear Diameter Total Gear Reduction Number of Steps for One Rotation Degrees for One Step Load Capacity 5.625 inches, 360 teeth double start, 64 pitch 960 : 1 46080 0.0078125º (0.
Appendix A CIRCUIT BOARD LAYOUT Pyxis Circuit Layout A-1
Pyxis 3-inch Circuit Layout A-2
Appendix B CIRCUIT DIAGRAM B-1
B-2
B-3
