THE GMap TOOL

Christoph Birk and Mark Phillips January 2001

1. Introduction

This document briefly describes the usage of Gmap, a tool created by Christoph Birk for quickly locating guidestars. GMap actually consists of two different tools: Skymap which displays guidestars available in the SAO, PPM, or HST Guide Star catalogs for any position on the sky, and Airmass which plots a graph of airmass vs. U.T., again for any sky position.

GMap is available for use at either the f/7 or f13.5 foci of the 40" Swope telescope. On the 100" du Pont telescope, GMap is now implemented for all instruments except the WFIRC (which has a similar tool integrated into its data acquisition software).
 

2. Setup Files

Three setup files are required to run GMap. These files must be located in the directory from which GMap is started (henceforth called the "working directory"), and must be named telescope.ini, guider.ini, and camera.ini. Original copies of these files corresponding to the various guider/camera possibilities are located in the /usr/local/lib directories of the 40" and 100" telescope data acquisition Sun Workstations "henrietta" and "dupontss". The setup procedure consists of copying the appropriate versions of these files into telescope.ini, guider.ini, and camera.ini.

2.1 40" Telescope

The first step is to copy over the telescope.ini file from /usr/local/lib to the working directory. Any directory will do, but it must be the one from which GMap must always be started. To copy the telescope.ini file, type:

     cp /usr/local/lib/telescope40.ini telescope.ini

Next the guider.ini file must be created. For the 40" telescope there are two possibilities corresponding to the f/7 and f/13.5 foci. These files are called guider7.ini and guider135.ini, respectively. Thus, to setup for using the IR camera on the f/13.5 focus, type the following in the working directory:

     cp /usr/local/lib/guider135.ini guider.ini

Finally, the camera.ini file must be setup. For the IR camera on the 40", the appropriate file is obtained by typing:

     cp /usr/local/lib/camera_c40irc.ini camera.ini

The appropriate guider.ini and camera.ini files for all instruments currently available on the 40" telescope are given in the following table:

2.2 100" Telescope

The telescope.ini file from /usr/local/lib must first be copied to the working directory. To do this, type:

     cp /usr/local/lib/telescope100.ini telescope.ini

Next the guider.ini and camera.ini files must be created. The appropriate files for instruments (except the WFIRC) currently available on the 100" telescope are as follows:

For example, if the TEK#5 CCD is to be used for direct imaging, copy over the appropriate file by typing:

     cp /usr/local/lib/guider_imb.ini guider.ini

    cp /usr/local/lib/camera_tek5.ini camera.ini

3. Starting up GMap

Once the setup files have been copied to the working directory, the GMap tool can be started by typing:

gmap &

Within a few seconds, a GUI window will appear. An example of how this window looks is shown below.

The telescope, guider, and camera are identified in the upper right hand corner of this window. The line below this gives the airmass, universal time, and sidereal time. (These are calculated from the Sun Workstation clock.) Below this line on the left hand side of the window are boxes for entering the right ascension (R.A.) and declination (Dec.) of the object to be observed. To enter the right ascension to read "10:38:29.1", point the mouse inside the R.A. box, type "10 38 29.1", and then hit the return key. To change the declination to "-03:03:31", point the mouse at the Dec. box, type "-3 3 31", and hit return.

The equinox of the coordinates can be changed by clicking the left mouse button on the Equinox box. Four options will appear: 1950, 2000, today, and set. If the last of these is selected, a dialog box will pop up which allows an arbitrary equinox to be entered. Changing the equinox will cause the coordinates to be precessed. Hence, the proper procedure for entering the coordinates of an object is to set the equinox first, and then to enter the right ascension and declination corresponding to that equinox.

The CassPos box allows the position angle of the instrument to be input. This is currently implemented only for instruments which are mounted on the IMB of the 100" telescope (e.g., CCD direct, B&C spectrograph, etc.). To change the CassPos value, point the mouse inside the box, enter a new value, and hit the return key.

Clicking the left mouse button on File in the GMap GUI pops up a menu with three options: Skymap, Airmass, and Exit. The Skymap and Airmass options are explained in the following two sections. As you might expect, the Exit option causes the GMap tool to terminate.
 

4. Skymap

Clicking on the Skymap option of the File menu in the GMap GUI causes a new window to appear which should look something like the following:

This window shows a map of the sky centered on the coordinates entered in the GMap GUI window. North is to the top and east to the left, with the scale being indicated in the upper left part corner of the window. The red box shows the position and size of the detector (in this case the NICMOS3 array of the 40" telescope IR camera), while the blue box illustrates the accessible guider field.

The position of the guidestars are shown as dots, with the size of the dots being proportional to the brightness of the star. Stars with know spectral types are indicated by the color of the dot; those for which the spectral type is not know are shown in black. Three different guidestar catalogs (SAO, PPM, and the HST GSC are accessible by clicking the left mouse button on the box labelled GSC. If the left mouse button is clicked on any particular guidestar, the name of the star, spectral type (if known), and magnitude will be displayed in the lower left corner of the window. Clicking the middle mouse button on a guidestar that falls within the boundaries of the blue guider field box will give the guider xy coordinates corresponding to this star. On the 40" telescope, these are the coordinates that should be entered in the GOTO box of the gdr GUI window; on the 100" telescope, ask the night assistant to set the IMB guider coordinates to these numbers. (Clicking the middle mouse button on a star outside the blue guider field box will cause the message "OUT OF FIELD" to appear.)

The Skymap tool can be used list the coordinates of any particular guidestar. To do this, first click the left mouse button on the star of interest. Next click the left mouse button on the Set box in the upper left corner of the Skymap window. This will cause the Skymap field to be centered on the star, and the coordinates of the star will be displayed in the R.A. and Dec. boxes of the GMap GUI window. This feature is useful, for example, for finding the coordinates of suitable focus stars when observing with the IR camera on the 40" telescope.

Finally, if you wish to close the Skymap tool without terminating GMap, simply re-select Skymap in the File menu in the GMap GUI.
 

5. Airmass

Clicking on the Airmass option of the File menu in the GMap GUI causes a third window to appear which should look something like the following:

This window graphs the airmass as a function of U.T. for the coordinates that have been entered in the R.A. and Dec. boxes of the GMap GUI window. The red dot shows the current airmass, and the blue line indicates how this will evolve with time. Note that airmasses above a value of 3 are not plotted. Changing the coordinates in the GMap GUI window will cause the airmass graph to be immediately updated. (Note that the maximum airmass to be plotted can be changed using a command line switch. For example, typing "gmap -a 5 &" will start GMap with a maximum airmass of 5.)

To close the Airmass tool without terminating GMap, re-select Airmass in the File menu in the GMap GUI.