pixels give an angular pixel size of 
0.31 arcsec/pixel, with a total square field of view of 150 arcsec on a side.|
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DIS Slitviewer for Beginners: Basic Usage Information
This page last updated: February 25, 2003 - JMD
This page last checked: September 14, 2003 - JMD
Apogee Slit Camera Manual Link Here
last updated 26 June 2003 by JCB
An Important Note About 3.5m Autoguding And The DIS Slitviewer
Although the 3.5m telescope tracks very well unguided over the course of many minutes, and performs even better with the NA2 autoguider, you MUST monitor the DIS slitviewer periodically! This can be done either by issuing the repeat command in the slitviewer software or be taking an exposure with exp commands every few minutes. Instances are known where object drifts very slowly off the slitviewer while the telescope is autoguding in particular parts of the sky where the rotator speed is large; by not monitoring the slitviewer, entire exposures have been lost due to this problem. To assure the quality of your data, remember to check the slitviewer (as well as your raw data!)
This manual describes how to operate the Apogee camera which is used as the slit viewing camera in DIS. This camera is operated by a separate program outside the normal Remark interface. For instructions on using DIS itself, see other documentation.
The Apogee slit viewing camera is made by Apogee Instruments and uses an 512x512 thinned, back-side illuminated SITe CCD for imaging the DIS slit. The 24 pixels give an angular pixel size of 0.31 arcsec/pixel, with a total square field of view of 150 arcsec on a side.
The reasons for switching from the old SBIG slit viewer to the new system are:
To run the software and be able to see the images, you must be:
The software will allow you to take images, with optional automatic dark subtraction, and will display these on your screen. You will be able to interact with the images to get pixel coordinates, values, etc., and adjust the color map both by adjusting the color map or by redisplaying with different contrast/brightness. Simple image centroiding is possible which will suggest instrument offsets needed to place the object in the slit. Images will be saved by default in /export/images/dis-slit, although the auto-saving may be turned off. If desired, the images can be automatically copies to your local machine using the secure scp, if you set up an account which allows remote access without a password (instructions later).
To start the program, you must first log onto tycho.apo.nmsu.edu using the visitor1 account (check with APO staff if you don't know the password). Once logged into tycho, execute:
to start the program. In reality, this will actually be running a program on another computer (offset.apo.nmsu.edu) to which the CCD is physically connected, but this is all transparent to you. A separate xterm window should appear on your screen with a status section in the top half, and a command section in the lower half. At the current time, you should not resize this window. Once you take your first exposure, a display window will appear with the image.
Hopefully this won't ever happen, but if the program appears to be totally hung up, you should be able to kill it using a CTRL- 
. Then restart it as above.
If you wish to interrupt an exposure (e.g., you entered an exposure time which is much too long), you should be able to do so using CTRL-C. This should stop the current exposure and return you to the command prompt.
All commands are case insensitive. The following commands are available:
Take an exposure of length time seconds.
Put program in never-ending loop of taking exposures of the last specified exposure time. Useful for guiding.
Stops the never-ending loop. CTRL-C serves the same purpose. The CTRL-C stop is immediate, while the STOP command will wait for the current exposure to terminate.
Sets up a window region on the CCD to read out. If no arguments are specified, you will be prompted to mark the desired corners of the box on the display window. Move the cursor to the desired corners and hit any key (although hitting reserved keys which also perform other functions (see below) may produce confusing results). Otherwise, if parameters are specified on the command line, the window will be set to region (x1:x2,y1:y2). When a subregion is read out, the overhead time for an exposure is shorter than for a full image. To restore to full-frame operation, use FULL command, or WINDOW FULL.
Restores full-frame operation if a WINDOW command has previously been issued.
You can get the program to print out instrument offsets from the cursor position or from a centroided position around the cursor by moving the cursor into the image display and using the C (centroid) or I (integer pixel) keys; see next section on image display window. Note that the program does NOT communicate at this time with the telescope, so it outputs instrument offsets which you will need to tell the telescope to make.
Changes the defined slit center to (xc,yc). Suggested offsets will be to this position. The currently defined slit center in shown in the status section in the upper part of the screen.
Change the default root file name to name. Default file name will be of form yyyymmdd where yyyy, mm, dd will be the UT date when the software is started. The filename extension will be .nnn.fits, where nnn will be an automatically incrementing number thats initial value will be the first number for which no file exists when the program is started. The filename for the next exposure is shown in the status section in the upper part of the screen.
Change the extension for the next file to be the number ext. If a filename with the new extension already exists, it will be written over by the next exposure.
Turn on/off automatic dark subtraction for images. If automatic dark subtraction is on, then a dark exposure will be taken before the light exposure whenever the exposure time is changed. If subsequent exposures are taken with the same exposure time, the original dark frame is re-used.
Set filetype for future image stores to be FITS. Actually, this is the only allowed filetype, so effectively, this command just turns on the automatic storage of images (in /export/images/dis-slit). This is ON by default.
Turn off autosaving of images. Turn this back on using FITS.
Turn on/off autodisplay of images after they are taken. On by default.
Turn on/off auto-transfer of images to your home institution after they are taken. Before turning on +XFER, you must set up a host and account to use with the ???? command. Off by default.
Redisplay the current image with greyscale scaling between low and high. You can also adjust the current colormap by playing with the colorbar in the image display window - see next section.
Sets mode for autoscaling to be based on mean and variance within image. This is the default.
Sets mode for autoscaling to have black level somewhat below mean level in image, and white level above it.
Sets mode for autoscaling of images to be from minimum pixel (black) to maximum pixel (white).
Sets scaling for future pixels to be identical to the current scale.
Changes the target temperature for the thermoelectric coolers. One must be a bit cautious not to set this too low or it will cause undue stress on the coolers. The coolers can probably reach 50 C below ambient. The default temperature is -30 C. It takes some time before a new temperature is reached after changing the set point.
Exits the program.
The first time an image is taken, the program opens an Image Display window on the console, and loads a color map as well as displaying the image. Once an image has been displayed, the Display window will accept interaction asynchronously of commands in the command window, provided that a wait for input, or any other I/O is not pending. To interact with the image, simply move the mouse onto the display window. The current pixel location of the cursor will be displayed in a frame at the base of the image display along with the pixel intensity. The arrow keys are used for find control (one pixel at a time) of the cursor position.
Important. If the image display window fails to open after the first image, it may be because of a problem with the program interacting with your X11 server. Make sure your X11 server is running in 8-bit PseudoColor mode; this is the mode which is required, e.g., for IRAF/XIMTOOL. If insufficient colors are available in the default colormap, the program will allocate a private colormap to proceed, in which case you may see the colors on your display switch as you move the cursor into and out of the display window. If you are using a private colormap, you will need to move the cursor into the display window to see the images ``normally''.
By default, the image window comes up as a moderately small window which shows a view of the image at 1/2 resolution. With mouse keys (described below) you can zoom into any region at full resolution. Alternatively, you can resize the window to a larger size and the program will automatically display images at full resolution if your resized window is large enough. This can be done at any time and does not require re-starting the program.
The image will come up with (1,1) in the lower left corner. With this convention, the image appears in the same orientation as it does on the sky. If the instrument is at 0 position angle, then N will be up and E to the left; obviously, if the instrument is rotated, this will no longer be true.
The following mouse buttons and keyboard keys are active while the mouse is located on the image display:
|
Button |
Function |
|
LEFT |
ZOOM IN, centered on the cursor |
|
MIDDLE |
ZOOM OUT, centered on the cursor |
|
RIGHT |
PAN, move the pixel under the cursor to the center |
|
Key |
Function |
|
R |
RESTORE image to the original zoom/pan |
|
C |
CENTROID around cursor position, and print out instrument offset required to put object at currently defined slit center |
|
I |
print out instrument offset required to put cursor position at currently defined slit center |
|
+/= |
BLINK Forwards through the last 4 images. |
|
-/_ |
BLINK Backwards through the last 4 images. |
|
P |
Find the PEAK pixel near the cursor & jump the cursor there |
|
V |
Find the LOWEST pixel ("Valley") near the cursor & jump the cursor there |
|
# |
"Power Zoom" zoom at the cursor to the maximum zoom factor |
|
H |
Toggle between small and full-screen cross-hairs |
|
] |
Clear boxes and stuff off the image display |
If you place the mouse on the color bar, these commands are available to adjust the contrast of the image:
The position of the mouse cursor displays the range of intensities represented by that color.
Pressing the R key while the mouse is on the color bar restores the original color map (undoing any change of the contrast or "roll" changes made with the mouse buttons).
When you issue the slitview command from tycho, you are actually just starting a process on the computer to which the slit viewing camera is actually connected; this computer is offset.apo.nmsu.edu. As a result, you cannot kill the program on tycho itself. When slitview is started, it automatically kills any program which is currently talking to the camera before a new control program is started up. Only one user can connect to the camera at a given time. There is a command on tycho called killview which will attempt to kill any existing slitview processes on the remote machine.
If you have problems with the program, it may be a good idea to directly log onto offset.apo.nmsu.edu, user arc (password known by on-site personnel). Check to see if any processes are running the program slitview.linux. If you kill these, any running versions of the program should exit. On offset, there is a script, killview which will automatically do this for you. Then you can try to start the program again using the slitview command.