CFHT, Instruments, Detectors, IR, Redeye Manual: Chapter 6.


Pegasus Overview

With such a diverse assortment of users, the CFHT instrument control system had to be designed so that it could be quickly and easily mastered by visiting astronomers, yet provide the power and flexibility that the engineering staff demands. We believe the challenge of providing such an interface has been met through the development of the "Pegasus" operating environment. Visiting astronomers can intuitively navigate with relative ease through the system because the basic tools they need are provided with simple menus. Pointing with a mouse and selecting an option is much less demanding, especially at 14,000 feet, than trying to accomplish the same task from memory with a command line interface. Redeye, like all of the CFHT facility instruments, is operated through a Pegasus session, hence observers who are already familiar with running any of the facility instruments can quickly learn how to use Redeye. In fact, observers who are already familiar with FOCAM should find running Redeye to be a very similar task.

User Interface Session Layout

The Command Menu Bar

Figure 6.1 shows the general layout of a session. Across the top of the screen is the command menu bar. It includes a row of control buttons, a pull-down help menu, a pull-down session configuration menu, and a text window displaying one-line help messages. Each button in the menu bar initiates a set of instrument actions. These actions are grouped in specific "forms" in which user input is solicited. Put simply, the menu bar contains all of the necessary controls for observing sessions. Note that large complex forms take a longer time to open up, so be patient after clicking a menu button.

Figure 6.1 - The Redeye session layout is shown. Along the top of the screen is a menu bar through which all camera functions can be controlled.

Feedback Window

Down in the lower-right portion of the session window shown in Figure 6.1 is a system feedback window. Note that the instrument name is part of the title area. The feedback window displays information pertinent to the form being implemented. The start-up of a form usually outputs a line or two of text to the feedback window. User and instrument errors are listed there as well. The lines in this window can be scrolled to allow previously displayed output to be examined. It is in general wise to consult the feedback window often to monitor the progress of the session and requested operations.

Clock, Disk Meter, and CPU Meter

To the left of the feedback window in Figure 6.1 are three small windows displaying computer information for the user's convenience. The top window shows the percentage of disk space remaining. If the background color of this meter turns orange then the disk is nearing its storage capacity and the user should save some files to tape and delete them from the disk. Below that is a clock displaying the computer's system time. Below the clock is a CPU meter which display's the computer's processing load. The CPU meter can be helpful to diagnose a system malfunction. For example, if a process creates conflicts somewhere in the system, the CPU load will increase to non standard levels (a steep upward trend).

Console Window

This window is usually iconified (reduced to a small picture) in the lower left corner of the screen (see Figure 6.1). This is a simple HPterm window from which UNIX commands can be entered. It is generally of no use to the user/observer.

Image and Forms Location

A large fraction of the session window is devoid of any windows and is referred to as the root window. This is where forms will appear after clicking the desired menu bar button. It is possible to open several forms at the same time but keep in mind that the computer load increases proportionally as more forms are run in parallel.

Interacting with the User Interface

Mouse Control

Pointing (or moving on the screen) the mouse cursor at an object signals the computer of a possible interest in that object. Clicking the left mouse button selects the pointed object (like turning on or off an option) or performs the indicated action. Dragging the mouse cursor around the screen, while holding down the left button, is used to move objects around, change window sizes, or browse through a menu.

Active Window

The background window that covers the whole display screen and currently filled with "CFH" labels is called the root window. When the cursor is in this window it is shaped like a miniature dome. However, when the cursor is moved to a session window, it changes to an arrowhead (window frame) or an "I" (interior of the window). A window is considered "active" when the cursor is pointed at it. If no window is active, any keyboard input is lost. The most visible indication that a window is active is that the window frame changes color.

Menu Usage

Displaying a menu is as easy as positioning the cursor over a menu button and then pressing (but don't let go) the left mouse button. Now, drag the cursor down the menu. As the cursor moves each available selection will highlight. When the desired selection is highlighted, release the mouse button to invoke that selection.

Control Buttons

Most forms contain four selection buttons, namely "Accept", "Save values", "Defaults", and "Cancel". "Accept" changes all parameters, stores them, initiates any required actions, and closes the form. "Save values" changes all parameters, stores them for later use, and closes the form. "Defaults" resets the parameters to the system defaults which may or may not be useful. "Cancel" ignores all activity and closes the form.

Text Fields

The form may also contain other items such as small boxes that contain alpha/numeric quantities such as object name, exposure time, etc. To select these object fields for input one may either use < TAB> to go from one field to the next or move the cursor to the field and click the left mouse button. In either case, the desired field is highlighted upon selection, meaning keyboard input will be accepted.

Selection Buttons

Other buttons that may appear are toggle switches (on/off).Sometimes these buttons are mutually exclusive (like buttons on a car radio). For example, in the EXPOSE form, bias, dark, object, and flat are mutually exclusive since only one type of exposure may be taken. Such one-selection "radio buttons" are always shaped like diamonds. Square shaped buttons correspond to a selection of an option among several possibilities. A button is "on" when it appears as a filled diamond or box. Open diamonds or boxes are considered "off".

Status Icons

A status icon provides information about a running process. Examples of status icons include:

Figure 6.2 - An example of a status icon is shown. In this case the status of an exposure in progress is shown.

Getting Help

Currently no "help" is available on-line (read this manual!). We are planning to implement on-line help in the near future though.

Adjusting Your Environment

Moving Windows

To move a window first position the cursor in the title bar of the desired window. The title bar is the rectangular area across the top of the window with text in it. When properly positioned, the cursor is an arrowhead. With the left mouse button depressed, drag the window to the desired location on the screen.

Resizing and Layering Windows

The size of a window can be changed by grabbing the window's frame with the cursor, dragging the frame to the desired size with the left mouse button, and then releasing the mouse button. The cursor is positioned correctly for resizing a window when it has an arrowhead shape, indicating the direction in which the window will either grow or shrink. Note that some windows do not have a frame and therefore cannot be resized. To bring a partially concealed window to the front of the overlying windows without selecting from a menu, click anywhere on the window's frame with the left mouse button.

Iconifying a Window

Read this section with a grain of salt. While users are not encouraged to iconify windows, unless they are sure of the consequences, the more advanced users can definitely take advantage of this feature. Programs running in an iconified window continue to execute until they finish or halt because they require input from the user. A side-effect here is that it is possible to obstruct the observing process by having a crucial window iconified and awaiting input. To iconify a window, first locate the minimize button. This is the small square immediately to the right of the title bar on the window frame. Press the minimize button by clicking on it with the left mouse button. Poof - the window has been changed to an icon sitting on the lower left side of the root window. To move the icon elsewhere, position the cursor on the icon, press and hold the left mouse button, drag the icon to a new location, and release the left mouse button. Normalizing (change back to regular sized window) is done by simply positioning the cursor on the icon and double- clicking the left mouse button. Note that some windows do not have a minimize button. This is either because Pegasus does not allow such windows to be iconified, or it is not feasible to iconify them.

Summary of Tools

The following tools are found in the main menu bar in Redeye observing sessions:

These main menu options are described in detail in the remainder of this chapter.


A Redeye exposure is initiated by clicking the EXPOSE button in the menu bar and filling out the form. The user can enter the following in the EXPOSE form:

Figure 6.3 - The EXPOSE control form is shown.
Note that the observer and object fields are "sticky", i.e., remain the same through repeated exposures until edited again. The exposure type defaults to "object" when opening the form. The median data option provides an on-line capability for a fast and accurate combine algorithm for image sequences (iterations > 1). When the "normal" median data option is selected a background process starts (the process is currently handled by the summit Sparc station Wiki). After each image is recorded a copy is sent to Wiki in the IRAF file format. After completion of the entire imaging sequence a "combine" task is invoked. It is based on the well tested and widely used CCDRED/COMBINE task in the NOAO/IRAF data processing environment. After extensive testing, it was decided to use the "average sigma clip" option offered by this task since it leads to a final image with a mean identical to a "median" option, but with a standard deviation improved by 10-15%. The average sigma clip algorithm works the following way. First, a mean and a standard deviation value are computed for each set of images. After rejecting the min and max values, then pixels with values exceeding x times (x~3) the standard deviation are rejected, and a final mean value is computed. The current implementation of this option is extremely reliable and has been extensively tested. It is mainly intended to help with fast reduction of flats and darks.

Once the fields have been edited/selected, take the appropriate action with one of the 4 "control" buttons. A "Redeye status" icon will then appear (Figure 6.2) displaying the file name that has been automatically linked to the image being acquired. This name has the form of a number, representing the exposure number in the CFHT archive system, followed by a small letter: "o" for object, "f" for flat, "d" for dark, or "b" for bias. The extension ".fits" is added to indicate that the data on disk is stored in FITS format. The file name is a crucial parameter for locating data, either on the summit disks while observing, or on the CFHT archive system. The status icon also shows the sequence number of the exposure (if you are running a sequence), the status of the array controller ("expose" when the array is integrating, "readout" when the data is being read out) and a count-down timer indicating the remaining exposure time. Also, a set of 5 buttons appear on the bottom of the icon. They offer the following actions:

At the end of an exposure the image is transferred from the array controller to the summit disk and stored under the FITS file name that was automatically assigned to it. Also, a copy of the file is sent through the CFHT network down to Waimea, where it is automatically saved to an archive optical disk. In the event that data files are accidentally lost or deleted on the summit disk, don't panic, make a note of the file number, and have someone retrieve the file from the optical disk for you.

Filter Control

Filters are controlled remotely through the Pegasus session. Though two coaxial wheels are in the cameras, observers do not have to be concerned about wheel "logic" to manage filters. The data acquisition computer makes sure that one wheel is always in an open position so the desired filter in the other wheel is clear and in the optical path. To select a filter click on the "FILTERS" button in the main menu. Along the left side of the FILTERS form are diamond shaped radio buttons that should be clicked to select a filter. After making a selection, click on "Accept" to execute the change in filters. A pop-up icon will appear with an hourglass to indicate that the wheels in Redeye are in motion. When this window disappears, it is safe to proceed with exposures. Clicking on "Save values" will store the desired filter configuration in the form but will not execute a motion after the form closes.


The MODES form allows the user to select automatic or manual image display after an exposure, automatic or manual graphic display after an exposure, and to enable/disable the TCS link for proper communication between the data acquisition computer and the Telescope Control System computer. Crucial Information is passed through this link, including current telescope coordinates, astronomical time, etc., hence it should only be disabled when it is necessary to reduce the system overhead to an absolute minimum.

Figure 6.5 - The MODES control form is shown, which controls image display, graphing functions, and the TCS link.


The IMAGE form allows the user to display the image of his choice. After selecting or editing the fields, clicking "Accept" will start a new process call SAOimage with the following attributes:

Figure 6.6 - The IMAGE control form is shown, which sets the attributes of the image display session currently running.

Images are displayed with SAOimage, a display package originally created by Mike VanHilst at the S.A.O. It is a stand-alone image display package with associated built in functions. The CFHT version, "CFHTimage", has been modified to incorporate a few custom features primarily associated with MOS/SIS.

Figure 6.7 - An example of a Redeye image being displayed under SAOimage is depicted.

Several different areas are evident in the SAOimage window. First, a large display area, which is where the image is exhibited with the best resolution. Two small display areas are also used in the upper right corner of the window. The small display on the left represents the full image in the memory buffer. If a green box is in this display, this represents which part of the entire image is being seen on the large display area (under pan/zoom). The small display on the right is a zoomed portion of the image around the cursor. Changing the position of the cursor in the large display area changes the magnified view in this small window. A menu bar above the large display area is available for controlling the program. A greyscale is presented at the bottom of the window. The greyscale coding will change according to any modification of the look up table. A set of cursor coordinates in the upper left window area is listed above the large display area. When SAOimage is opened from "IMAGE", the coordinate display (i.e., X, Y position and intensity value) will update as you move the cursor around the large display area.

Modifying Image Scaling

For faint intensity levels select "scale" in the top menu bar, then "histeq" in the bottom menu bar. This will apply a histogram equalization to the image, with emphasis on the mode of the histogram. Most of the time, the mode of the histogram is close to the median sky level, so that the scaling is ideal for revealing faint objects. The selection of "color" in the top menu bar allows the user to modify the image contrast and thresholds by dragging the cursor in the main display area with the left mouse button. Note that in the color menu, "invert" can be selected to flip the look up table so that white represents the lowest value pixels. To see the highest intensity pixels in an image, select "scale", then "sqrt". This will compress the intensities and the look up table, thereby displaying only the pixels with the highest values.

Pan and Zoom

First select "Pan" in the top SAOimage menu bar. In order to pan around the image, position the cursor on the image location that you would like to see in the middle of the display, then click with the left mouse button and the selected image area will move to the center of the display. One can also use the full image display in the top of the window to control panning. Specifically, dragging the green box with the left mouse button to the desired region of the image, then releasing the mouse button, will update the image in the main display area. Zoom is controlled in the bottom menu bar after the "Pan" button is clicked. A set of zoom options ranging from to 4 are available. Clicking on any of these buttons will magnify the image by the zoom factor. Alternatively, clicking with the middle mouse button in the main image display yields progressively greater zoom levels. To unzoom click on "zoom1".

Other useful features in SAOimage include:


The GRAPH form controls plots of cuts across an image. The control options include:

Figure 6.8 - The GRAPHER control form is shown. This tool creates line plots of cuts across selected rows or columns in images.

GRAPHER is an interactive plotting program. The actual plot window opens after "Accept" is selected in the GRAPH form. It provides the following possibilities (see Figure 6.9):

Figure 6.9 - An example of a grapher line plot is shown.

IQE (Image Quality Evaluation)

The IQE form controls the computation of various statistics from a FITS file. These include simple minimum and maximum values, as well as more complex values such as mean, standard deviation, full- width-half-maximum, and centroids. At the top of the IQE form is a large field for the FITS file name. This is the file on which statistics are performed, and all locations, both entered and reported, will be relative to this file in pixel units.

Figure 6.10 - The IQE form is shown. This tool reports basic statistics of input FITS files and is particularly useful for quick assessments of seeing or focus quality.

Subraster Options

The subraster options are used to define the image region in which statistics are computed. The use of the entire FITS file to compute statistics is not recommended, due to the nature of the calculations. For example, the centroid values reported from a FITS file containing more than one star will be between the stars! The user is responsible for selecting a subraster the only includes objects that statistics should be computed on. To accomplish this, first select the radio button labeled "As Follows", and then fill the desired values into the "Xc", "Yc", "Xs", and "Ys" edit fields. Use the picture in the lower right of the form as a guide to the meanings of these variables. It is expected that you will use an image display tool (SAOimage) to determine coordinate values. If the FITS file only contains the items you are interested in, users can select the "Entire data area, ignoring edges" radio button.

Values computed: This area of the form is used to select the desired computed values, using a list of check-boxes.

Background from: This list is used to define the background for FWHM computations. Values can be generated as the mean of the entire edge of the selected area, which is normal for images. For spectroscopic data, the use of the first and last X (or Y) values may give a better approximation of the actual background. Selection is via a radio button.

Other options: The FWHM values are usually computed based on the maximum pixel's X and Y coordinates. If the entire area selected is useful for the calculations, the "Collapse for FWHM/PWHM" may be selected. This may be useful for spectroscopic data.

IQE output: After the "Accept" button is pressed, the computed statistics are presented in a pop-up window, as text. After viewing the results, press the "Quit" button that appears across the bottom of the this output window.


The FILES form allows 4 types of action on FITS files, namely

Figure 6.11 - The FILES control form is shown. This form is used to select and then manipulate Redeye image FITS files.

The actual FITS files can be selected through several techniques using the FILES form. Specifically:

After selecting the desired files and action, pressing the "Accept" button will execute the desired action. As each file is processed, it is listed in a pop-up window. When the last file has been handled, a message is displayed confirming this fact and the pop-up window can be closed with the "Quit" button. As files are listed in this pop-up window, those that have been saved to tape will be surrounded by parentheses. It is suggested that the "List Files" action be used to verify that the files desired have in fact been selected and then bring the FILES form up again to perform any action.


To end the Redeye Pegasus session, click on "ALOHA" in the main menu bar. This will bring up another form which asks if you want to really quit ("Accept") or resume your session ("Cancel").

Figure 6.12 - The ALOHA form used to exit a Redeye Pegasus session is shown.