The SKY program has been an essential planning and instrument control tool for Keck observers and Observing Assistants since its release in late 1992. SKY was used to commission the first Keck science instrument, NIRC. From its humble beginnings as a program to point the telescope to a given target, SKY has evolved into a sophisticated graphical interface for previewing Keck target parameters. SKY now provides observers with the capability to Verify starlists., Preview observations., Create Star Charts., Create finder charts using DSS images., Search for guide stars., and Compute position angles. Complete instructions for carrying out these procedures are given below.

Starting SKY

1. Log into a Unix workstation running Solaris. (Although a SunOS version of SKY exists, it lacks some of the major functions available in the Solaris version.)
2. Right click on the desktop to bring up the window manager's pulldown menu, and select:
   Keck-menu --> SKY --> SKY(inst)
   Options for SKY on the pulldown menu include:
   • SKY (K1 NIRC) if using NIRC
   • SKY (K1 LWS) if using LWS
   • SKY (K1 LRIS) if using LRIS
   • SKY (K2 AO) if using the Adaptive Optics System
   • SKY (K2 ESI) if using ESI
   Note that several instruments do not have a dedicated SKY version. For Keck I instruments, use LRIS. For Keck II instruments, use ESI.
3. After a few seconds, the SKY main window should appear on your terminal (see below for an example with LWS)
   SKY: main window on startup for LWS

Verify starlists

Follow these steps to load a starlist into Sky.
1. Click on the File button in the upper left corner of the main SKY window.
2. Select the Open... option. The Open Star List window will appear.
3. Select your starlist directory from among the choices in the Directories list. Double-click on the directory name to activate the directory.
4. Select your starlist file from among the choices in the Files menu. Double-click on the filename to read it in.
5. The objects read from your starlist will be printed in the text output field within SKY. The output should have a format name RA DEC EQUINOX. See the example below.
   SKY: main window with targets verified
6. Carefully review the list to ensure that all targets were correctly input.
   Problems:
   • RA not read properly --- the most common problem with starlists is not having the RA begin in column 17!
   • Digits missing --- double check that the starlist conforms to the required format.
   • Bad format for a target --- Output in sky will read:
     "Line #: Bad star format" see example below:
     SKY: main window with targets verified

Preview observations

1. Load a starlist: (see above)
2. Select a target: Click on the line containing the target to highlight it. The target name and RA/Dec coordinates will transfer to the corresponding boxes near the top of the SKY window.
   The Az/El coordinates in the main SKY window will update every time a target is selected. To get the current as an el of a selected target, reselect the target.
3. Enter the sidereal time in the ST field if you want to check the availability of a target at a later time or leave the default which is set to the current sideral time. Times may be entered as floating points or sexagesimals value ( 12.5 or 12:30)
4. Enter a desired SKY position angle (SKYPA in degrees) in the box labeled Rotator (Optional). The default is 000.0. Allows observers to estimate the physical rotator angle.
   SKYPA is generally defined as the angle of the vector from the science instrument detector to the guide camera, and hence does not generally correspond to the direction of detector columns as projected onto the sky, as you might expect. Please consult your instrument specialist for clarification.
5. Click on the PREVIEW button. The Preview Telescope/Rotator Move window will appear.
   SKY: main window with targets verified

• Target Name Name of target as printed in the starlist.
• Telescope time to limit: The number of hours and minutes remaining until your target becomes inaccessible to the telescope.
• Above limit The siderial time at which the target will first become accessible. If the rising time has passed, the time appears in blue; if the object has yet to rise, the time appears in red.
• Below limit The siderial time at which the telescope can no longer access the target. If the setting time has passed, the time appears in blue; if the object has yet to set, the time appears in red.
• Rotator data
  • time to limit:The number of hours and minutes until the rotator can no longer track the object. When its limit of travel is reached, the exposure must be stopped or paused while the rotator angle is changed by 360°. For certain declinations, the rotator will never reach a limit; in this case, the message No limit is given.
  • rotpdest, the physical or ``drive'' angle of the rotator
  • rotdest, the ``user angle'' of the rotator
  • direction, the sense of rotator motion (CW=clockwise, CCW=counter-clockwise)
  • CW limit, the clockwise limit of rotator travel
  • CCW limit, the counter-clockwise limit of rotator travel
  • instrument, the name of the assumed instrument
  • par angle, the current parallactic angle for this object

Create Star Charts

1. Load a starlist: (see above)
2. Select a target: Click on the line containing the target to highlight it. The target name and RA/Dec coordinates will transfer to the corresponding boxes near the top of the SKY window.
3. Set the magnitude range: Adjust the two horizontal sliders in the box labeled V to set the V mag range for the catalog search.
4. Click on the LIST button. The Star Chart window will appear.
   Problem: Image not displayed
   1. Select from the pulldown menus
      Options --> Set Defaults to bring up a "Set Defaults" subwidget.
   2. Select Yes in the Star Charts? field (see image below).
      Set Defaults with "Star Charts?" Yes selected. Other options are blurred.
   3. Retry clicking on the LIST button.

What the star chart shows

• position, title, and coordinates of the target (center of the window)
• fields-of-view for various instrument components (cyan rectangles)
• positions of catalog objects targets within the window (black circles)
• positions of various pointing origins projected onto the sky (red circles)

Star Chart example with LWS at the pointing origin

Star chart actions

• Show/Hide labels Click the Show Labels button to label all stars with their titles. Click again to hide them.
• Change position angle The circular blue buttons in the upper right corner change the rotator angle clockwise or counterclockwise. The magnitude of the change is given by the number lying between the up and down arrows between the circular buttons; click on the arrows to increase or decrease the value. The current rotator angle is listed in green digits to the lower left of the plot.
• Select pointing origin Click the left mouse button on the name of the desired pointing origin (red words at right of the plot) to change the current selection. For example:
  • click LRIS if your target is to be imaged using LRIS, or if your target position is the center of the slitmask.
  • click SLIT if your target will be observed using LRIS in longslit mode
  • click POL if your target will be observed using LRIS in polarimetry mode

Search for guide stars

1. Create a star chart either with or without a DSS overlay.
2. Select the appropriate pointing origin for your target by clicking on the red labels at the right of the plot.
3. Adjust position angle as needed in order to place a guide star within the guider field of view (FOV). If you are unsure which of the light blue boxes represents the guider FOV, consult your instrument specialist. The position angle is adjusted by clicking on the circular blue buttons at the top right-hand corner of the Star Chart plot. The angle increment may be adjusted by clicking the appropriate arrow button in between these circular buttons. (Note: if using custom slitmasks with LRIS, you must use the position angle for which the mask was designed).
4. Note the optimal position angle and ask the OA to use this position angle when acquiring the target during the night.
5. If using the LRIS offset guider, also note the guider position value nearest to your star (tiny, light blue 3-digit numbers running along the side of the guider FOV)

Compute position angles

1. Create a star chart as described above.
2. The circular blue buttons in the upper right corner change the rotator angle clockwise or counterclockwise. The magnitude of the change is given by the number lying between the up and down arrows between the circular buttons; click on the arrows to increase or decrease the value. Use these controls to rotate the field of view as desired.
3. Note the rotator angle, listed in green digits to the lower left of the plot. This is the value to give the OA when setting up for the field.

Create finder charts using DSS images

1. Create a star chart as described above.
2. Click the DSS button at the upper right of the Star Chart.
3. After a delay of about 15 seconds, the DSS image will appear on your star chart.
4. Note that some of the line graphics showing the fields of view, stars, etc., may be obliterated when the DSS image appears. To restore the graphics, use the window manager's Refresh function available by clicking the titlebar of the Star Chart window.

1. From the window manager's pulldown menu, select the Programs menu.
2. Select Snapshot... to launch the snapshot utility. Within a few seconds, a new window will appear.
3. Click the Snap button to start a grab operation.
4. Move the mouse cursor onto the SKY graphics window and click the mouse button to grab the window's contents.
5. Click the right mouse button on the Print menu, and select the Options item to define the orientation, scale, and destination for the plot.
6. Click the Print button to send the plot to the printer.

1. From a local (i.e., not punaluu ) Unix prompt, type
   xv
   and wait for the xv program's main window to appear.
2. Move the cursor into the xv window and press <CTRL>-g to start a ``grab'' operation. An xv grab window will appear.
3. Click on the Grab button. A beep will sound.
4. Move the cursor onto the Star Chart window.
5. Raise the window if necessary using the Front button at left of the keypad.
6. Click the left mouse button to grab the window. A copy of the star chart will appear in the xv main window.
7. Move the cursor back to the xv window.
8. Click the right mouse button to bring up the xv controls menu.
9. Click left mouse button on the Print button in the xv controls window to bring up the xv prompt window.
10. Click on the Grayscale button. The xv postscript window will appear.
11. Click on the OK button to send the plot to the printer.
12. Press q in the xv main window to quit xv.