C40 Telescope Control Program
Table of Contents
- 1. C40 Command Summary
2. C40 Command Syntax
3. Starting the Program
4. How to Set the Coordinates
5. Slewing the Telescope
6. Bob's Box
7. Coordinate Catalogs
8. How to Take Date to Check or Update the Pointing Model
|<Esc>||Immediately abort any dome or telescope move.|
|<F1>||Display help screen.|
|MP n.n||Set the coordinate display to show mean place for the year n.n.|
|AP||Set the coordinate display to show apparent place.|
|OP||Set the coordinate display to show observed place.|
|TP||Set the coordinate display to show corrected values according to the telescope pointing model.|
|Time and Coordinate Commands:|
|UT n n n.n||Set the UT to n n n.n.|
|RA n n n.n||Enter the RA coordinate n n n.n.|
|DEC n n n.n||Enter the Dec. coordinate (+/-)n n n.n.|
|ROFF n.n||Set the RA offset to n.n sec of time.|
|DOFF n.n||Set the Dec. offset to n.n arcsec.|
|CSET||Change the RA and Dec. offsets so that the coordinate display agrees with the coordinate inputs.|
|GUIDE||Activate telescope guiding.|
|IDLE||Turn off telescope guiding.|
|SLEW||Slew the telescope to the position entered with the commands RA and DEC.|
|COVER||Park the telescope at the south pole to allow easy removal of the dust cover.|
|ZENITH||Slew the telescope to the zenith.|
|DOMEFLAT||Slew the telescope (and move the dome) to dome flat position.|
|Bob's Box Commands:|
|RBB n.n||Set the RA increment to n.n arcsec.|
|DBB n.n||Set the Dec. increment to n.n arcsec.|
|NN||Move telescope north. Also EE, SS, WW.|
|NE||Move telescope north and east. Also SE, SW, NW.|
|ZBB||Set the home position (zero the cumulative values).|
|HBB||Move telescope to the home position.|
|DOME AUTO||Turn on automatic dome tracking.|
|DOME IDLE||Turn off automatic dome tracking. Also DOME STOP.|
|DOME PARK||Park the dome to the south.|
|DOME n.n||Set dome mode to manual and move to n.n degrees azimuth.|
|LOAD filename||Load the catalog "filename".|
|OBJ n||Load the coordinates of catalog object n into the commanded position.|
|CAT n||Store the commanded RA and DEC to catalog object n.|
|LIST||List the currently loaded catalog to the system log.|
|SAVE filename||Save the current catalog to "filename" on the floppy disk.|
|CLEAR n/ALL||Clear catalog entry n, or clear entire catalog.|
|Q||Exit from the program.|
|EAST||Set telescope mode for east side of mount.|
|WEST||Set telescope mode for west side of mount..|
|Diagnostic and Engineering Commands:|
|TERM n||Open a terminal on COM port n (1-3).|
|VER n||Set message log verbose level to n (0-2)..|
|<F2>||Dump system log to file TEMP.LOG.|
|<F3>||Dump screen to file SCREEN.BMP.|
|<F5>||Append telescope positions and sidereal time to POINT.LOG.|
|<F6>||Toggle motion logging (encoders).|
|<F7>||Dump motion log to MOTION.LOG.|
|<SCROLL LOCK>||Pause log output. Scroll log with up, down, left, right keys and PageUp, PageDown, Home and End keys.|
- DEC-0 25 47.2
- DEC -0 25 47.20
will both set the Dec. coordinate input to -00° 25' 47.2". The backspace key moves the cursor back one character at time. All commands are terminated by a <CR>.
The program will begin displaying telescope data as long as the computer is connected to the various serial lines, independent of the power switch on the telescope.
Note that the UT date is initialized from the internal computer clock, which MUST be set to the correct UT date and UT time. The user is prompted to enter the correct UT time when the program starts. If the UT time displayed is correct then just press . The UT can be updated at any time with the UT command.
The command prompt is a "*" in the lower left box on the screen. All system commands are entered in this box. The cursor is invisible, but it is always at the end of the command string.
Set the coordinate display to show mean place coordinates for a given year by using the MP command. The coordinate system is the FK5 (IAU 1976) system (e.g. J2000.), which is very slightly different from the FK4 (e.g. B1950.) system. However, the difference between the two systems (for example between J1950. and B1950.) is negligible. The coordinate system in use is shown just above the green RA and Dec. display.
Type "AP" to set the coordinate display to show apparent place. Apparent place includes the effect of nutation (amplitude 10 arcsec) and aberration (amplitude 20 arcsec), so apparent place coordinates are NOT the same as mean place coordinates for the time of observation. DON'T use apparent place unless you are setting to a position which has been precessed to apparent place. DON'T use coordinates which include the effect of atmospheric refraction, since this effect has already been taken out by the control program.
The telescope can be slewed to a given position under computer control. ALL TELESCOPE SLEWS MUST BE MADE WITH THE MOVABLE PLATFORM AT ITS DOWN POSITION. First enter the target coordinates using the RA and DEC commands, these coordinates will appear in the RA and DEC display in the system command box. The SLEW command will then slew the telescope to this position. If the target is at an aimass greater than 3 then the SLEW command will not work, and the telescope has to be set with the control consol. If the dome is in AUTO mode then it will move to the target location on the sky while the telescope is slewing.
The telescope can be set to the zenith with the ZENITH command. The observer is asked if the movable platform is parked before the telescope is moved. The command COVER will slew the telescope to the south pole to allow easy access to the dust cover. Be sure to return the platform to its down position immediately after removing or replacing the dust cover. The command DOMEFLAT will move the telescope (and the dome) to point to the flat field screen to allow the observer to take dome flats.
A system message will appear when the slew has been successfully completed. At the moment, the north slew relay occasionally sticks closed after a long slew to the north, and the telescope will want to continue to move in that direction for the next slew. If this happens, a system message will appear, and the slew will be halted. The observer should wait a minute or so for this condition to clear before attempting the slew again. Note that this can occur at the end of a slew as well, and it will seem as if the completion of the move is delayed (the telescope does not converge on the requested position, and the "Slew Complete" message is delayed).
Any telescope motion can be immediately aborted by hitting the <Esc> key.
The Bob's Box function keeps track of the cumulative motion in RA and Dec. Use the ZBB command to zero the cumulative values. This establishes a "home" position. The HBB command will move the telescope back to the home position. The screen display shows the size of the RA and Dec increments and the cumulative motion. Moves generated by external serial line control will be shown next to the Ext: label.
Note that the encoder that is presently being used on the declination axis has a resolution that is less than 1 arcsec, and so the requested move may not be accurately indicated by the new declination position. The declination stepper motor does have a resolution of better than 1 arcsec.
- nnn hr min ss.ss (+/-)deg min sec.sec
with one star per line. Each catalog can contain up to 999 objects. To use a catalog, first remove the boot floppy disk in the computer and load your catalog disk. The command LOAD filename will read the catalog "filename" from the floppy disk into the program. The coordinates for object number n in that catalog can be loaded into the commanded RA and DEC in the coordinate input box with the command OBJ n. The user can then, for example, slew to that position with the SLEW command. The commanded coordinates (note, not the position of the telescope) can be saved to object n in the catalog with the command CAT n. The contents of the loaded catalog can be listed to the system log with the command LIST. The command SAVE filename will save the contents of the currently loaded catalog to the file "filename" on the floppy disk.
While you are waiting (or during the afternoon), login as "obs40" on the Sun computer (Henrietta) in the console room, and start IRAF in an xgterm. Now type "pointing" to load a special pointing task. In order to run a pointing model, it is necessary to have a file containing a grid of fairly evenly spaced alt/az positions. In the directory "/export/data/obs40/pointing" you should find three files called "grid42", "grid49", and "grid61" which have coordinates for 42, 49, and 61 grid points, respectively. Alternatively, you can generate your own grid file by typing "makegrid" in IRAF. You will be asked to enter the following parameters:
- Number of azimuth bands
- Number of altitude bands
- Lowest altitude (in degrees)
- Highest altitude (in degrees)
- Amount of randomness (in degrees)
- Output file name
A grid of alt/az positions will then be written to the output file. This file may will be used as input to the "get_pointing_stars" task (see below).
When you start observing, slew to a star in the bright star catalog. Choose a focus for an expected temperature and DON'T CHANGE IT, since the star image sometimes moves around when the secondary focus is adjusted. Zoom the guider camera lens in or out, and adjust the position of the star until it doesn't move when zooming the lens. This defines the optical axis. Do a "cset" on the TCS computer at this position, and record the offsets. Finally, remove the boot floppy disk and load your own floppy (make sure it has plenty of space available on it!).
Now type "get_pointing_stars" in the IRAF window on Henrietta. This task will ask for the name of the file with the grid points that you wish to use. It will then print the coordinates of the nearest bright (~9th mag) star in the PPM catalog corresponding to the first alt/az position. The task will then pause in order for you to set the telescope on the coordinates of the star. Be sure to set the coordinate display to show the epoch (to 2 decimal places) of the star coordinates that have been printed out by the "get_pointing_stars" task. (Do this by typing "MP 200X.XX" before slewing to the first star.) Once you have slewed to the position of the star, center it on the optical axis. (Keep the guide camera zoom at the widest setting.) Now turn off the pointing model by typing "TP" on the TCS computer, and set the RA and Dec offset to zero ("ROFF 0" and "DOFF 0"). Next, press the <F5> key. This writes the true coordinates, the present coordinates and the present sidereal time to the file POINT.LOG on the floppy disk. Now toggle back on the pointing model ("TP") and reenter the original RA and Dec offsets. You are now ready to slew to the next star. To get the coordinates of this star, hit "return" in the "IRAF" window where the "get_pointing_stars" script is running. Repeat this procedure until the "get_pointing_stars" script finishes.
The file POINT.LOG can be used as input to the analysis program TPOINT. The output model from TPOINT is used as the pointing model for the telscope. Make sure to record the outside temperature, barometric pressure (in millibars), and humidity at the time that the pointing data are taken, as these will also be required by tpoint.