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

Graphical User Interface

Starting the Graphical User Interface
Setup Menu
Go Menu
TV Menu
File Menu
Math Menu
Options Menu
Engineering Menu
Help Menu
Motion Control
Image Display Screen

After typing GEMINI/LICKTCS and hitting the RETURN key, the Menu Start-Up Screen appears. Please examine this screen.

The cursor will be flashing inside the display box. Use the arrow keys to move up and down the list.

Everything else should be fine if this is the first entry of a normal startup. If it is a re-entry after a crash, then some of the default parameters will be wrong. For instance, the First File will not be 1, but some other number -- consult your log sheet. In addition, the various wheels will have been left in the positions they had just before the crash.

To change these, use the down arrow to reach the required item and the right arrow to produce an additional "drop down menu". Again use the down arrow to locate the item to be changed and press RETURN.

Press the ESC key to exit this Start-Up screen. The changes will occur and the Main Menu Screen will update. Now examine the Main Menu Screen shown below.

The top line (red background) contains the DATE, INSTRUMENT TITLE and current TIME.

The second line (blue background) contains 9 entries. These are the HEADERS for "drop down" menus. You can access each menu by

  1. pressing the "key letter" indicated by a green highlight, e.g. S, for Setup
  2. moving the mouse to the appropriate header and clicking once on the left button.
If you access the wrong menu by mistake, don't panic! Either move the mouse to the correct menu and click again or press the ESC key.

The options on the blue menu line are Setup, Go, TV, File, Math, Options, Engineering, Help, and Quit. We will return to these in a moment.

The third panel from the top (gray background - orange border) is an INSTRUMENT STATUS PANEL. It has five columns. The instrument property is in black and the current status of that property is displayed in red. The key items displayed in this panel are (from left to right):

Imaging, Polarimetry, Spectropolarimetry
Telescope control system interface, usually Lick Observatory
If this area is blank, then no actions are in progress. If it is flashing "TV",
then it means that control currently resides with the other (image) display terminal.
Focal Plane Aperture Wheel Status:
Auxiliary Wheel Status:
Dichroic Slide Status:
Open (default), Spot, Long Slit, Double Slits
Open (default), Polarizer, Calcite Prism
K @ LW channel (default) or K @ SW channel
WavePlate Slide:
WavePlate Rotation:
Calibrator; not implemented
Two positions, In or Out
0, 22.5, 45, or 67.5

The fourth column gives the status of the PC to transputer link (PC-TLink). Also displayed are the detector temperatures. NOTE: at present these are not updated by the computer.

The rightmost block in the status display area describes 3 "flags":
If FileOvWrt = OFF, then you CAN overwrite existing files of the same name.
If FileOvWrt = ON, then the file protection is activated.
AutoDisp:= ON (default) means automatic display of each image.
AutoScale: describes how the image display has been scaled. The default setting takes the MEAN of the data frame as an offset and then selects a gain which matches the lowest remaining signal to black and the highest signal to white.

Current Observing Setup:

The fourth panel from the top (pale blue background - black border) displays the setup for the current observation. The left and right segments respectively refer to Channel A (the shortwave (SW) channel with the NICMOS HgCdTe array) and Channel B (the longwave (LW) channel with the SBRC InSb array).

These panels display the setup in current use or the integration that has just ended. The entries in these panels correspond directly to those in the lower black panel called NEXT OBSERVING SETUP. Changes to the observing setup are made in the lower panel only. We will return to this critical feature in a moment.

Integration Time Display:

Between the pale blue and the black setup panels is a graphical display which actively tracks the progress of the integration. A bar increases in length from 0% to 100% as the integration proceeds and a countdown display gives the Itime and Co-adds remaining. This countdown is a timer and does not perfectly reflect the overhead required for multiple readout modes; occasionally this overhead will cause the display to count down "negative co-adds".

Function Keys:

Below the black panel containing the Next Observing setup is a thin dark blue panel with white lettering describing the FUNCTION keys which provide a single keystroke action for frequently used command sequences.

F1direct access to the Channel A setup panel
F2direct access to the Channel B setup panel
F3executes a SCRIPT; enter the script name at the prompt
F4takes an exposure in BOTH channels and saves the data in FITS format in the next available file in a Date/Integer sequence of the form 26SEAnnn.fts or 26SEBnnn.fts, where nnn is the running file number and a two-letter abbreviation is used for the month.
F5same as F4 but for Channel A only; Channel B is not updated
F6same as F4 but for Channel B only; Channel A is not updated
F7displays again the last image in Channel A
F8displays again the last image in Channel B

When F7 or F8 is used, control is transferred to the NEC "display" monitor so that the various function keys defined for image display can be used.

To return control to the main Instrument Console you must press the ESC key.

The final bar (gray background) at the bottom of the Gemini Instrument Console displays special commands available by pressing the control (CTRL) key and the Function key together. The most important of these are the ABORT keys:

CTRL F4 ABORT the twin-channel integration started with F4
CTRL F5ABORT the Channel A integration started with F5
CTRL F6ABORT the Channel B integration started with F6

One control key has a special function

CTRL F8forms the difference of the last two frames taken in each channel and displays the result. The difference is taken in the order of (Previous Frame - Most Recent Frame).

Setup Menu:

Press the S key to get the drop-down menu for Setup (shown next), or click the left mouse button when the cursor is on the word Setup in the blue menu bar.

This menu provides access for setting up both channels, changing the position of any motor-controlled mechanism (Motor Setup), sending a command to TELCO to move the telescope (also available as CTRL F1) and back to the General Setup menu.

More about Next Observing Setup: Access Channel A from the Setup menu, or press F1; now type in your Object name and press Return. Do the same for Itime and the number of Coadds. You can also use the down-arrow key to step down through the list to the item you want.

When you press the right-arrow key at the Filter entry, a menu will appear which lists all the filter options available for that channel.

Use the up and down arrow keys to move to the filter you want, or press the key letter highlighted in green. To get out of this menu, after or without making a change, simply press the ESC key.

SampMode and MulReads are used to select the detector readout mode and the number of multiple reads when "Fowler sampling" is chosen.

SampMode 1Single-sampling (default)
SampMode 2Correlated Double Sampling (CDS)
SampMode 3Fowler Sampling; set by MulReads
SampMode 4Movie Mode (to be implemented
SampMode 5Multiple Convert per pixel with single sampling
SampMode 6Multiple Convert per pixel with CDS
SampMode 764x64 subarray (fast channel only) single sampling
SampMode 864x64 subarray (fast channel only) CDS
SampMode 9128x128 subarray (fast channel only) CDS
Note: No setting of MulReads is necessary in SampMode 6; any displayed value is ignored.

To leave the Next Observing Setup panel press the ESC key. There will be a verification/warning panel (in red) with the words "Is this correct? (Y/N)". Respond by pressing either Y for yes or N for no. Hitting Return will yield the default (Y). Repeat entire setup process for Channel B.

Go (and Abort) Commands:

Clicking on the GO entry in the Menu Bar (or pressing G) will reveal all of the possible options for starting and stopping integrations (see below).

Display (TV) Commands:

Images are automatically displayed if the AutoDisp flag is on. Previous images can be redisplayed by using the TV menu shown below.

Clicking on TV A or pressing F7) displays the last image in Channel A and transfers control to the "display" monitor. To display a previously stored image you can click on the TV File. The TV Setup option allows you to change feature such as AutoDisp and AutoScale.

File Commands:

By clicking on File (or pressing the F key) you can access several useful features for manipulating files, including the ability to save a Test frame (see below).

Math Commands:

The most frequently used math operation is to form the difference of the last two frames - to obtain a "sky-subtracted" image - so this feature has a function key CTRL F8. Other math features can be obtained by clicking on Math (or pressing M). Diff A and Diff B form and display the difference of the last two frames in Channel A and B, respectively. Diff File takes the difference of any two files. General arithmetic operations are also available. Phot Setup allows the magnitude zeropoints in each filter to be preset.

Options Command:

This is an important menu item which contains all of the SCRIPT editing, checking and running features. Writing scripts is discussed in detail elsewhere. By clicking on Escape to DOS, it is possible to exit to the DOS prompt. Instructions are given on how to return to the Gemini Menu.

Engineering Commands:

The next command on the Menu Bar is called Engineering. Included in this option are commands for initializing motors (Motor Init), reading the microswitch settings of each mechanism (Motor Read Switches) and re-setting the transputers (PC-T Reset). It is advisable to do a PC-T Reset after every telescope slew, as the long cables to the instrument pick up noise from the motors and can disrupt communication between the instrument and computer transputers. Failure to do a PC-T Reset may result in having to reboot the computer.

The Temperature Read command is yet to be implemented. Timing Setup is an engineering feature not available to users.

Help Commands:

Help is available on-line for several items, e.g. how to write scripts, minimum integration times. Phone numbers and "user notes" are also included.

Motion Control: The default setup of the instrument leaves the Aperture and the Auxiliary wheels in the OPEN or clear position, the Dichroic set to send the K light to the LW channel and both the SW and LW Filter wheels are at the Blank or Dark position. If these need to be changed then return to the General Setup menu and select Motor Setup as shown below. Use the right arrow to see the options for each item, e.g. Focal Plane Aperture Wheel. Click on the one you want, or move to it with the arrow keys and press RETURN.

IMPORTANT: Before moving the dichroic slide, ALWAYS initialize the dichroic motor from the Engineering Motor Init menu, then move the dichroic to the wanted position. If you do not follow this procedure, the dichroic may get stuck in the K@LW position (which requires opening the vacuum dewar to fix).

Image Display Commands:

The Image Display screen has its own set of commands; many function keys are mapped to different commands when in the Image Display mode. The Image Display is accessed by pressing F7 or F8, for channels A and B respectively. Control is returned to the main User Interface by pressing ESC. Within the Image Display, there are several sub-menus, which are accessed through the function keys. Control is returned to the general Image Display by pressing ESC, it will often be necessary to hit ESC twice.

Image display screen is shown below.

Plots are displayed in the non-active channel. To redisplay that image, simply hit F7 or F8 again. Control may be transferred between channels without returning to the main User Interface.

The following are the Image Display commands. Unlike the main User Interface, these are not accessible through hot-keys or mouse selection.

F7 - Atransfer control to channel A
F8 - Btransfer control to channel B
CTRL F7 - Filedisplay a file
CTRL F8 - Invertinvert and image (set display gain to -1)
F9 - Profiledisplay a X,Y profile centered on the cursor
F10 - SpPlotdisplay a spectral plot
CTRL F10 - Contourdisplay a contour plot of the image
F11 - Astrometryperform astrometry on the image, with TCS option
F12 - Photperform photometry on the image
CTRL F12 - Statscalculate statistics within a user selectable region
ARROWS - Cursormove the cursor
CTRL ARROWmove the cursor in steps of four pixels
INS/PGUP-DNchange the display gain
DELchange the display offset
HOME/ENDzoom in/out on the image
ESCquit display (or subdisplay)


These keys place control in the A or B channel display. You may switch between these directly, or return to the main User Interface by pressing ESC. Basic information about the image is displayed below it -- filename, itime, co-add, mean, standard deviation. In addition the pixel value at the cursor is displayed, as well as the cursor coordinates. All pixel values are displayed for 1 co-add (that is the image is divided by the number of co-adds).

You may reposition the cursor using the arrow keys. Pressing CTRL and the arrow keys simultaneously will move the cursor in steps of four pixels. When control is transferred from one channel to the other, the cursor remains on the same pixel number.

The image is displayed with a default display offset and gain. Any pixel below the offset value is displayed as black. The default value depends on the parameters selected in the TV Setup menu. To change the offset, press the DEL key and enter a new value; then press ENTER. Similarly, to change the display gain, press INS, enter a new value and then press ENTER; alternately, you may increment or decrement the display gain using the PAGE UP and PAGE DOWN keys.

The image can be magnified using the HOME key, which will "zoom in" on the image, centered on the cursor. To "zoom out" press the END key. To return to the full screen, exit the Image Display by pressing ESC, and then redisplay the image using F7 or F8.

Each time control is re-transferred to the image display, the image is redrawn.

CTRL F7 -- File

Pressing CTRL and F7 together will display a file. You will be prompted for the file name. The file directory will default to the current data directory (see General Setup). The input for the filename has a limited number of characters, so you may need to change the default in order to display a file from another directory.

CTRL F8 -- Invert

Pressing CTRL and F8 together will invert the current image without changing the offset.

F9 -- Profile

This key displays an X and Y profile centered on the cursor position. The profile is tens of pixels wide in both directions.

F10 -- SpPlot

Pressing F10 will prepare to display a spectral plot. The program will prompt, in the window below the image, for the rows to be averaged into the plot and the parameters of the plot. The plot will automatically cover the entire range of displayed columns; if the image has been zoomed-in, the plot will only be across those columns.

CTRL F10 -- Contour

Pressing CTRL and F10 together will display a contour plot of the image. The plot will always cover the entire image. You will be prompted for the floor and ceiling for the plot.

F11 -- Astrometry

Pressing F11 will enter Astrometry mode. The program will prompt for two cursor positions. The distance between these positions will be calculated and displayed. Then, if the LICKTCS is in use, you will have the option of moving the telescope that distance, without exiting this mode.

F12 -- Phot

Pressing F12 will enter Photometry mode. To return to Image Display at any time, press ESC. The photometry function will calculate the flux in a box, subtract the sky from a sky box around it, and convert the flux to an apparent magnitude based on a zeropoint. The photometry box is centered on the cursor, as is the sky box.

The size of these boxes may be changed using ALT-ARROW keys. To make the "star box" bigger or smaller, press the ALT key and the UP or DOWN key simultaneously. The box is always square. To make the sky box bigger or smaller, press the ALT key and the LEFT or RIGHT arrow key simultaneously. To change the zero-point, press the INSERT key. To calculate the photometry, press the ENTER key.

All photometric information is displayed in the window below the image.

CTRL F12 -- Stats

Pressing CTRL and F12 simultaneously will enter Statistics mode. To return to Image Display at any time, press ESC. Statistics mode will calculate the mean and standard deviation in a box. To move the box use the arrow keys. (HINT: it is faster to move the cursor before entering the Statistics mode, since the box must be redrawn each time the cursor is moved). To change the size of the box (which does not have to be a square) press the ALT key and any of the ARROW keys simultaneously. To calculate the statistics, press the ENTER key.

Last modified: Mon Dec 23 12:01:45 PST 2013 by Elinor Gates