The first thing to decide is what you want to take an exposure of and how you want to calibrate it. There are basically two ways to calibrate: using a star, or using arc lamps. To use a star, either pick the Object+Star mode or the Full Sequence mode. To use arc lamps, pick the Object+Lamps mode or the Full Sequence mode. To not use any calibration, pick the Object Only mode, and to only move the mechanisms and not take an exposure, pick the Setup Only mode.
Next, you?ll want to determine the nod pattern to use. Nod stare does not move the telescope before taking an exposure; it simply takes one exposure with the slit in its current position. The numbered nod positions divide the slit into the same number of pieces as the number following Nod and takes exposures in the center of these pieces. Nod 2 moves the telescope from center up to one fourth of the slit length from to the top of the slit, takes an exposure, moves down to one fourth of the slit length from the bottom of the slit and takes another exposure. Nod 3 performs a similar action, except the three positions where exposures are taken are one sixth of the slit length from the top and bottom, and in the center of the slit. Nod 4 is also similar, where the four exposures are taken at one eighth of the slit length from the top and bottom and one eighth the slit length above and below the center. Nod Chop uses the numbers set by the Set Nod Parameters dialog in the Telescope section of the main menu to determine how much to nod. This is slightly different than normal nodding, because often times, the object will be completed moved out of the slit.
Now, determine the number of nod repetitions to make. You can repeat the nod pattern from one to six times.
Next, determine the Spectral Mode you wish to use. In the High Resolution mode, both the echellogram and the cross dispersor are used to produce a complete echellogram. In the Low Resolution mode, the echelle grating is replace with an LR Flat mirror that passes the light from the cross dispersor to the detector. In imaging mode, the light is not dispersed at all, an is instead passed to the detector as it had when it passed through the slit.
After that, determine the slit and filter to use for the exposure. The filter determines which wavelengths are detected, and the slit determines how much light is passed in and how wide the spectral features are. An important aspect to note than may not be obvious is that only certain slits are intended to be used for each Spectral Mode. In the High Resolution mode, the slits with slitlengths of 12" and 24" are intended to be used. In the Low Resolution mode, the 42" slits are intended to be used.
Now, position the setup box to set the echelle and cross dispersor angles. These angles determine which parts of the echellogram fall on the detector. Move the box by dragging it or by using the arrow keys so that the desired portion of the echellogram falls inside the box.
Lastly, enter information about the Object and Star, if necessary. Often, certain parts of this area may be disabled. This is because some of these fields only apply to certain calibration modes. For instance, in Object Only mode, no information about the calibration star is needed since no calibration star is used. Furthermore, for Setup Only mode, this entire area is disabled, since no exposure at all is taken. If necessary, enter the object and star names, and the integration time and coadds for each. If the mode supports multiple setups, enter the box number that corresponds to the setup you which use for the current exposure.
When all of the above is done, your configuration is done. Now you are ready to turn your configuration into a script.
From a Configuration to a Script
Once you have your configuration set up the way you want it, you can either save it to a file for execution later, or execute it immediately. To save it, hit the Save Configuration As? option from the File section of the main menu. This brings up the Pickfile dialog. Pick a file to write to or enter a filename in the filename box. Be sure to include the extension *.csh so that loading the file will be easier.
To execute the script, hit the GO button. This saves the script with a default filename consisting of the date and a file number with the *.csh extension, written to the default script directory. These files are the scripts the DRP looks for when a script is running. Next, after the script has been written, the EFS spawns a C-Shell for the execution of the script. Then, it is up to the server to carry out the commands.
While the script is running, the EFS is still fully functional, allowing the you to setup another configuration while waiting for the running script to finish. To stop the execution of the currently running script, hit the red ABORT button.
Setup boxes, when properly utilized, can save valuable time, as well as reduce the work by automating the data collection process. By using setup boxes, you can condense multiple scripts into one, and by simply hitting the Go button, you can sit back and watch the EFS take as many exposures as desired.
It may take a bit of experimenting to become comfortable with the manipulation of setup boxes. This section is intended to help you reach that comfort level by introducing a few techniques in setting up your configuration.
Moving Boxes
To move a box, click somewhere in the box, and move the mouse while
holding the mouse button down (i.e. dragging the mouse) until the box is
in the desired location. If you click somewhere in the echellogram that
is not occupied by a box, the current box snaps to that location, centered
about the point clicked. The current box can be moved in small increments
by using the arrow keys.
Creating New Boxes
Setup boxes are only allowed in Object and Object+Lamps calibration modes. A new box can not be created unless you are in one of these modes. To create a new box, hit the New button. The new box is drawn in the center of the echellogram and colored yellow, while the old box?s color changes to green. The box colored yellow is the active or "current" box, while green boxes indicate the inactive boxes. The new box always becomes the current box. You can enter create a new box anywhere in the chain of boxes. Boxes that fall after the new box are shifted in number by one.
Changing the Current Box
There are two ways of switching between boxes: 1) by hitting the Previous or Next buttons until the desired box is current; 2) by simply clicking within the box you want to make active. If you click in an area occupied by more than one box, the current box is decided by the following: 1) if one of the boxes is already the current box, it remains the current box; 2) otherwise, of the remaining boxes containing the point that was clicked, the box with the highest number becomes the current box.
You may have noticed that when in a calibration mode that does not allow multiple setup boxes, the current box ( Box 1, the only box allowed ) follows you when you change filters, Spectral Modes, etc. This also happens for the current box in a multiple box setup. For instance, now you have two boxes, Box 2 is active, and Box 1 is inactive. If you change another filter, Box 2 follows you and is now centered in the echellogram of the new filter. Box 1 is still in the same position is was in the previous filter. To see this, hit the previous button.
Deleting Boxes
To delete the current box, hit the delete button. If the current box is not the last box, all the boxes with numbers higher than the deleted box get shifted down, so that there is continuity. For example, if you have 6 boxes and you delete box 3, boxes 4 through 6 become boxes 3 throught 5 respectively. Their setups are the same; only their numbers change. If the box deleted is the last box, the current box becomes the one previous to the deleted box. Otherwise, the current box number remains the same, but reflects the change in numbering, and therefore represents the box that was one after the deleted box. Using the above example, the current box is still number 3, but has the configuration of what Box 4 had before the deletion.
Using Multiple Boxes
One use of multiple boxes is to take a sampling of images in the various filters. The most importing thing to remember is that once you have a box where you want it, before switching to another filter for your new box, create the new box first. Remember, if you change filter, the current box comes with you. To avoid this, create a box, making it the current box, then change filters. This also applies to switching between Spectral Modes.
Another common utilization of setup boxes is to create a "postage stamp" of the echellogram. This is the use of multiple boxes to cover the entire filter bandpass. For example, lets say you wanted the entire echellogram for the Nirspec-6 filter. When you bring it up in the EFS, you notice that one box is two small to cover the entire echellogram. Therefore, use multiple boxes. Move the box to the so that it covers the lower left corner of the echellogram (e.g. echelle: 62.5, Cross Disp.: 33.34). Then hit New. Move that box to the lower right of the echellogram (e.g. e.: 63.84, c.d.: 33.42). Hit new two more times and move the two new boxes to cover the top half of the echellogram (e.g. e.: 62.25, c.d.: 35.19, e.: 63.95, c.d.: 35.16). If necessary, adjust the four boxes so that the entire echellogram is covered. Now you are ready to expose!
The use of Arc lines are a valuable resource to the astronomer in terms of calibration and setup. However, the User Lines feature of the EFS is another powerful tool, allowing you to customize existing lists, and to create your own lists. The EFS can then plot the lines specified in your list over the simulated echellogram, giving you the ability to adjust your setup so that the desired line(s) fall on the detector.
To enable the User Lines, hit User Lines under the Overlays section of the main menu. This brings up a dialog that lists the user line list. To open an existing line list, hit the Browse button. Then select the desired file, and hit the okay button. The list is displayed in the box. To start a list from scratch, simply start adding lines. If a list is already displayed, and you want to start a new list, hit the Clear List button. This will remove all lines from the list box.
To add a line to the list, simply type the wavelength (in microns) in the Add Line to List: box. If you want to add a comment to the line, perhaps describing which line it represents, enter the text in the New Line Comment: box. When the new line is ready to be added, hit the Add button. The line is added and the list is automatically sorted from the shortest wavelength to the longest. If you want to remove a line from the list, click on the line in the list and hit the Remove Selection button.
Once you have the list the way you want it, you may save it if you like.
Do this by typing the filename in the Save List As: box and/or hitting
the Save button. The pickfile dialog is brought up and you can select a
file to write to or enter the name of a new file in the box.
If you are ready to plot the lines on the echellogram, hit either the OK button or the Apply button. The OK button will close the dialog, while the Apply button will leave the dialog open. If the list has been modified in anyway, hitting OK will prompt you to save the list if desired. Hit Yeas on the prompting dialog to save the list to a file, hit no to plot the lines and close the dialog without saving the list.
Before you plot the lines however, you may want to select the color
for plotting. To do this, hit the Select Color button. The current color
is shown in the box next to the button. If you hit the button, a new dialog
is created. The box on the top shows the currently selected color. To adjust
the color, move the sliders for the Red, Green, and Blue to the desired
color. To adjust the Color System, click on the Select Color System menu,
although, this is usually unnecessary. The RGB system is the default. The
following table shows some sample colors in the RGB system.
RGB | Color | EFS Line |
255, 200, 50 | Yellow-Orange | Neon |
220, 220, 220 | Light Gray | Argon |
255, 100, 0 | Red-Orange | Krypton |
100, 255, 100 | Light Green | Xenon |
200, 200, 0 | Yellow | OH |
255, 0, 255 | Magenta | User Lines Default |
255, 255, 255 | White | None |
0, 0, 0 | Black | None |
0, 255, 255 | Cyan | None |
A special, useful feature of the user lines list is the ability to enter
a Z to simulated a redshift of a spectral line, so that the lines in the
list are plotted on the echellogram where the would fall if there were
shifted by the specified amount. Redshifted wavelengths are determined
using the relation:
By using this feature, if the object?s Z is known, it is easy to determine
which filter and echelle and cross disperser angles to use to make sure
the desired line falls on the detector.