User's Guide to the Gemini Twin-Arrays Infrared Camera

Table of Contents

Quick Reference
What is Gemini?
Summary Table
Quick start - for the expert
Not so quick start - set-up
Graphical User Interface
More About Gemini
Signal-to-Noise Estimates
Sampling Modes
Writing Scripts
Observing Recipes
Computer Setup
Testing the Arrays
Instrument Maintenance and Trouble-Shooting

Mt. Hamilton Homepage

Writing Scripts

The Gemini user interface software provides a script or macro capability that allows the user to put together any number of commands to be executed sequentially as a group, in much the same way as a UNIX shell-script or a VMS command procedure. This feature is especially useful for carrying out a repetitive observing/operation sequence, such as making a mosaic and doing repetitive engineering tests. The script tool is provided in both the menu interface mode and the command line mode.

List of Script Commands
Create a Script File
Execute a Script File
Example Script File

Script writing tool Currently does basic dithering scripts.

List of Script Commands

Almost all of the command-line commands are allowed in a script file file. However, it is recommended not to use commands that must run interactively in a script because of possible confusion during the script execution. Therefor, a list of script commands is created and given below which are proven to be rather useful in real observations. This script command list can be accessed on-line from the Gemini software menu mode under the Help item in the root menu.

System Commands
BEEP 0-10000generate beeps for 0-10000 milliseconds
CONFIRM strprint confirmation information str
DISKSPACEcheck free disk space
DO 1-1000iteration operator for script file
ENDDOiteration operator for script file
ECHO strecho string str
PAUSE num strpause system num sec (0=indefinite) and print str
Observing Setup Commands
COADDA 1-9999set number of co-adds for channel A
COADDB 1-9999set number of co-adds for channel B
FILENUMA 1-9999change image file running number for channel A
FILENUMB 1-9999change image file running number for channel B
FILTERA filternamechange filter for channel A
FILTERB filternamechange filter for channel B
ITIMEA 0.000-999set itime (seconds) for channel A
ITIMEB 0.000-999set itime (seconds) for channel B
MULTIA 2-9999set number of samples for multi-sampling mode, channel A
MULTIB 2-9999set number of samples for multi-sampling mode, channel B
OBJECT strset current object name
SAMPMODEA 1-6set sampling mode for channel A (1=single, 2=CDS, etc)
SAMPMODEB 1-6set sampling mode for channel B (1=single, 2=CDS, etc)
OBSMODE Imaging|Polar|SpPolarchange observing mode
STPAP Open|Spot|Sinslit|Dblslitchange aperture wheel position
SPTAUX Open|Calcite|Polarizchange auxiliary wheel position
STPDIC K@LW|K@SWchange dichroic slide position
STPWPS Out|Inchange wave plate (IO) position
STPWPR 0|22.5|45|67.5change wave plate (rotation) position
STP_INIT Ap|Aux|SWF|LWF|Dic|Pol|WPS|WPRinitialize stepper motor
Observing Commands
Go A|B|2start integration for channel A, B, or both
MOVIE A|B|2start movie mode for channel A, B, or both
TEST A|B|2take test frame(s) for channel A, B, or both
TV Display Commands
TV A|B|2|filenamedisplay channel A/B frame or FITS file filename
TV_DISP On|Offturn on/off TV auto-display
TV_GAINA 0.001-1000set TV display gain for channel A
TV_GAINB 0.001-1000set TV display gain for channel B
TV_OFFSETA +/-32767set TV display offset for channel A
TV_OFFSETB +/-32767set TV display offset for channel B
Math & File I/O Commands
IMDIFF A|B|2calculate image difference and display
IMSTATS A|B|filecalculate statistics for channel A or B frame or file
SAVE A|B|2save test frame from channel A or B or both
WDISK A|Bwrite channel A or B frame to disk in FITS
Telescope Control Commands
TELMOVE x ymove telescope by x arcsec in RA and y arcsec in DEC
TELPOSNread current telescope position (RA, DEC, HA)
AUTRETSET p x yset autoguider reticle positions p=0 for guide reticle, p=1 for background reticle, x and y are the pixel positions of the reticle
AUTRETGETread current autoguider guide and background reticle positions
For more information on using autretset in scripts see

A few of the commands in the list are specifically designed for the script tool, such as BEEP, CONFIRM, ECHO, and PAUSE and the iteration operators DO and ENDDO.

Create a Script File

A script file is created or edited using the DOS screen editor. The DOS text editor can be invoked from inside the Gemini user interface program. In the menu mode, select Edit Script under the root menu item Option. In the command line mode, escape to DOS and run the editor directly. Script files are placed in the directory C:\GEMINI\SCRIPT and have the file name extension .SCR. When editing a script file in the menu mode, simply give the name of the script and the Gemini program will add the directory path and extension to it.

Each command must have one line in a script file, but it can start from any position in the line. Blank lines are allowed and a comment line starts with #. The following is an example.

# A test script file

# set parameters

# integrate
DO 3
Like in the command line mode, if a command parameter is not supplied in a script file, the program will prompt for the parameter during the execution.

The script tool provides a syntax check feature which checks the validity of a command and the validity and value range of its parameter. For example, a script with the following two lines

will yield the following error messages when running a syntax check:
CL Error: invalid command - line 1 > ITIME 10
CL Error: parameter value out of range - line 2 > COADDA 0
Script syntax check: 2 error(s) found
No syntax error is generated if a command parameter is not supplied in a script. The program will not make a syntax check when the parameter is entered during the execution.

To run the syntax check in the menu mode, select Check Script in the Option item. In the command line, type CHKSCRIPT {filename}.

Execute a Script File

The Gemini program always makes a syntax check first when running a script. If an error is found, the script execution is aborted before any command is executed. To run a script, select Run Script in the Option item (hot key CF3) in the menu mode or type SCRIPT {filename} in the command line mode.

During the execution, the command currently being executed is displayed in both interface modes. The next command will also be displayed in the menu mode. For example, the script execution status

3:7 > GO A 4:7 > FILTERA H
shows that the script file has a total of 7 command lines and the command being executed is the 3rd command line GO A; the next command to be executed is FILTERA H.

A script execution can be aborted by pressing the function key CTRL F2. Note: the software will say press CTRL F3 to abort the script - this is incorrect. CTRL F2 is the abort command. The execution stops only after the current command execution is finished. Therefore, to abort and active command in a script such as an integration immediately, press CTRL F2 first and then use the normal abort command.

IMPORTANT NOTES: If you are in the TV mode when a command execution is finished, you must come back to the text mode in order for the next command in the script to get started. Also, do not switch between the menu mode and the command line mode or escape to DOS during a script execution or the execution status display will get messed up.

Example Script File

# script to make a 1x9 mosaic
ECHO script to make a 1x9 mosaic

# set observing mode
OBSMODE imaging

# turn on tv display

# set observing parameters

# confirm setup; Y to continue and N to quit
CONFIRM Is the setup correct?

# start 1st integration
GO 2

# loop 8 times
DO 8

# pause to turn off guider
PAUSE 0 Turn off guider

# offset 160 arcsec north

# pause to find guide star
PAUSE 0 Find guide star

# integrate
GO 2


# beep 3 sec to wake up
BEEP 3000

Last modified: Thu Feb 15 15:49:05 PST 2007 by
Elinor Gates