Lick Infrared Camera User's Guide

Data-Taking System Guide

The Lick data-taking system developed by Richard Stover, has evolved over more than a decade. Its latest incarnation runs under X-Windows. The program was adapted for use with LIRC-II by Kirk Gilmore.

The data-taking program initially creates three windows: an xterm window displaying the data-taking menu, an image window, and an image control window. Some commands invoke submenus or additional windows. Following is a summary of the commands found in the LIRC-II version of the program.

Data-Taking Menu

A. Selection number allows preselected parameters to be saved and recalled.
Changes made to the current parameters with options `B' through `I' are saved under the active selection number and can be recalled by selecting that number (see selection `J'). Ten complete settings can be recorded.

B. Integration time sets the length of the exposure in seconds.
This option sets the exposure time in seconds. Note that changing this option during an exposure will not change the integration time. To do so, the `Change integration' command (selection `V') must be invoked. The actual exposure times elapsed and remaining are displayed in the upper right part of the screen during an integration.

C. Observation number numbers the current observation.
The observation number will be stored as part of the header. The observation number, preceded by the letter `d' and with the extension `.ccd' appended, is the filename given that image on disk (e.g., observation number 3 will be labeled `d3.ccd'). An existing file with the same name will be overwritten. The observation number only increments if an observation is recorded. Note that the displayed observation number represents the next image that will be recorded to disk, whereas the displayed tape number, if any, shows the last image recorded to tape.

D. Window defines the portion of the device to be read out.
The window is specified by height (rows), width (columns), and origin. The origin is counted from the upper left corner of the window. The LIRC-II window size is customarily kept at the full 256 x 256 pixels.

F. Observation type defines the observation as `normal' or `dark'.
Note that in the absence of a shutter, there is no difference between normal and dark. LIRC-II darks are made by moving the filter and/or lens wheels to their `dark' positions.

G. Recording selects the data storage medium.
Options are `disk,' `tape,' `both,' or `not recorded.' Note that when `not recorded' is selected, the current image will be written to the scratch file /scratch/scr.ccd, but will be overwritten by the next unrecorded observation. `Disk' refers to the disk directory /data, or, when that unit is full, to the /vista directory. `Tape' refers to the Exabyte 8-mm cassette drive. To save time, most users write LIRC-II images only to disk during observations, and save them to tape at the end of the night.

H. Display next image on the terminal

I. Object allows entry of a label that will be attached to the image.

J. Selection summary lists the ten preset selections (selection `A').

K. Number of erases sets the number of erases before the exposure is begun.

L. Number of prereads sets the number of bias frames taken before the exposure is begun.
The frames are automatically taken, stored, coadded, and averaged, then subtracted from the actual exposure during readout. Setting the number of prereads to zero disables the function.

M. Number of Coadds sets the number of target frames to be coadded before recording.
The requested number of frames are added in the computer memory, before the final image is dispalyed and written to disk or tape. Only the summed image is saved. The saved image is given the observation number of the first image in the coadded series, so that when using coadds, observation numbers on disk will not be consecutive. To take individual, non-coadded images, set the number of coadds to one.

R. Start starts the exposure.

S. Stop stops the exposure, reads out the chip, and records the data. The user is prompted for confirmation.

T. Abort stops the exposure and discards the data. The user is prompted for confirmation.

V. Change integration changes the integration time during an exposure.
The actual exposure times elapsed and remaining are displayed in the upper right part of the screen during an integration (selection `B').

W. Change selection changes the preset parameter selection during an exposure (selections `A' and `J').

X. Comments allows up to five lines of comments to be added to the current header or, if preceded with an asterisk, to all headers.

?. Help invokes on line help.

Z. Special invokes a five-option sub-menu, of which parts of options 2 and 3 are most commonly used and are further described here.

2. Tape
  1. Prepares a new tape for writing. Use this selection only with new or recycled tapes. Once initialized, any previous data on the tape will be lost.
  2. Rewinds a tape and then positions it to the end of last exisiting file (end of volume mark). Option `C' is usually preferred.
  3. Reads the current tape position and then positions it to the end of the last existing file (end of volume mark).
  4. Writes the last image to tape.
3. Miscellaneous
  1. Accepts observer's name(s) for header.
  2. Accepts instrument description for header.

Image Display and Image Control Windows

Note: A more complete manual for these windows is now available.

The data-taking system creates an image window for displaying incoming raw images, and another for interactive control of the image window. The windows may be moved and sized as you would any x-window.

When the cursor is placed in the image window, the array coordinates and DN at the current cursor position are displayed in the upper left corner of the control window. For precise positioning, the cursor may be moved in the image window by using the arrow keys. The following commands are available when the cursor is in the image window.

To draw a row or column plot at the cursor positon: Place the cursor on the image at the desired row or column. Type `r' or `c', for a row or column plot. A blue plot window is spawned, displaying the plot. When the cursor is placed in the plot window, the values of X and Y are displayed in the upper right-hand corner of the plot window.

To limit the x-axis of a plot: Plots made as described above may be rescaled after they are drawn, by drawing a box on the plot itself, just large enough to contain the area of interest. Draw with the mouse while holding down the left-hand button, then click on `apply box' in the upper right-hand corner of the plot window. Clicking on `no zoom' restores the original plot. Alternatively, a box may be drawn on the image itself by typing `b' with the cursor in the image window, and clicking and dragging to define the upper left and lower right corners of the box. Row and column plots made with the cursor inside the box will have only the extent of the box.

To draw rapid consecutive plots across the image: Hold down `r' or `c' while moving the cursor on the image. This provides a fast method for assessing the whole frame.

To see a magnified portion of the image, centered on the cursor: Activate the magnifying circle at the upper center of the image control window by placing the cursor on it and clicking the left-hand mouse button. Return the cursor to the image. A magnified view of the area around the cursor appears in the circle.

To recenter the image around the current cursor: Click the center mouse button with the cursor at the desired place on the image. This is useful as a first step to zooming in on a particular part of the image (see below).

Other options for manipulating and interacting with the image are available in the image control window, pictured in Figure 8. On-line help for image control functions may be invoked by placing the cursor on the command in question and clicking the middle mouse button. A few of the most commonly used functions are described below.

Figure 8. The image control window

To enlarge or reduce the image: With the left-hand mouse-button, click on the appropriate number, representing the magnification, in the upper-right portion of the window. The size and position of the image, with respect to the image display window, is graphically represented in the box at the upper right center of the control window. The green and black outlines represent the image and the display window, respectively.

To pan: Move the cursor to the box at the upper-right-center of the control window; the cursor will become a black dot. Place the dot on the representation of the image (green outline) at the point you wish to be at the center of the redrawn window. Click the left-hand mouse button. The image is redrawn in the display window at the new position.

To expand or contract the range of the bitmap: Move the cursor to the right-hand end of the solid blue, horizontal bar. When the cursor has changed to a left- slanting arrow, hold the left-hand mouse button and drag the bar right to expand the bitmap range, left to contract it. The image will be redrawn using the new bitmap range. The longer the blue bar, the lower the contrast.

To change the zero-point of the bitmap: Move the cursor onto the solid blue, horizontal bar, hold the left-hand mouse button and slide the bar right or left.

To change the correspondence of the colormap to the bitmap: Move the cursor onto the vertical color bar on the right side of the control window. When the cursor has changed to a spray-can, hold the left-hand mouse button and drag the cursor up or down. The color map changes instantaneously. To apply an entirely different color map, invert the image, draw contour lines, or change to black and white, use the controls under the `Color Ctrl' heading at the lower-left-center of the window.

To retain the current bitmap (ie. prevent autoscaling of new images): Click on the `Lock' button.

To clip pixels lying beyond the range of the bitmap (ie. prevent wraparound): Click on the `Clip' button.

To perform statisitics on portions of the image: Select `Itv' under the `Options' heading at the lower-right-center of the window. This will invoke another window with several options. The most commonly used is the `Stellar Stats' command, which calculates and displays, in yet another window, a variety of useful information about the selected object. First click on `Pick Stellar Stat Loc', move the cursor onto the image, and click on the object you wish to analyse, then click on `Do Stats'.

To see numerical values over a portion of the image: Select `Digitals' under the `Options' heading at the lower-right-center of the window. Click on the region of the image for which you want imformation. A window appears, displaying a matrix of values for the pixels surrounding the selected region.

To display an image stored on disk: Select `New Image' under the `Options' heading at the lower-right-center of the window. Another window will appear with a directory of available images. Display the desired image by clicking once on its filename. By default, the last ten images written to the data disk are listed. You can change the directory and number of images listed by clicking on the appropriate boxes and replying to the prompts, and then clicking `display new image list'.