The Script Builder ToolToolsScript Builder
TDE applications can be controlled externally from another program,
from a console prompt, or from a shell script using the Desktop
COmmunication Protocol (DCOP). KStars takes
advantage of this feature to allow rather complex behaviors to be
scripted and played back at any time. This can be used, for example,
to create a classroom demo to illustrate an astronomical concept.
The problem with DCOP scripts is, writing them is a bit like
programming, and can seem a daunting task to those who do not have
programming experience. The Script Builder Tool provides a
GUI point-and-click interface for constructing
KStars DCOP scripts, making it very easy to create complex scripts.
Introduction to the Script Builder
Before explaining how to use the Script Builder, I provide a very
brief introduction to all of the GUI components;
for more infomation, use the "What's This?" function.
The Script Builder Tool
Script Builder Tool
The Script Builder is shown in the above screenshot. The box on the
left is the Current Script box; it shows the
list of commands that comprise the current working script. The box
on the right is the Function Browser; it
displays the list of all available script functions. Below the
Function Browser, there is a small panel which will display short
documentation about the script function highlighted in the Function
Browser. The panel below the Current Script box is the
Function Arguments panel; when a function is
highlighted in the Current Script box, this panel will contain items
for specifying values for any arguments that the highlighted function
requires.
Along the top of the window, there is a row of buttons which operate
on the script as a whole. From left to right, they are:
New Script, Open Script,
Save Script, Save Script
As..., and Test Script. The
function of these buttons should be obvious, except perhaps the last
button. Pressing Test Script will attempt to
run the current script in the main KStars window. You should move
the Script Builder window out of the way before pressing this, so you
can see the results.
In the center of the window, there is a column of buttons which operate
on individual script functions. From top to bottom, they are:
Add Function, Remove
Function, Copy Function,
Move Up, and Move Down.
Add Function adds the currently-highlighted
function in the Function Browser to the Current Script box (you can
also add a function by double-clicking on it). The rest of the
buttons operate on the function highlighted in the Current Script box,
either removing it, duplicating it, or changing its position in the
current script.
Using the Script Builder
In order to illustrate using the Script Builder, we present a small
tutorial example where we make a script that tracks the Moon while
the clock runs at an accelerated rate.
If we are going to track the Moon, we will need to point the display
at it first. The lookToward function
is used to do this. Highlight this function in the Function Browser,
and note the documentation displayed in the panel below the Browser.
Press the Add Function button to add this
function to the Current Script box. The Function Arguments panel
will now contain a combobox labeled dir, short for
direction. This is the direction in which the display should
be pointed. The combobox contains only the cardinal compass points,
not the Moon or any other objects. You can either enter
Moon in the box manually, or press the
Object button to use the Find
Object window to select the Moon from the list of named
objects. Note that, as usual, centering on an object automatically
engages object-tracking mode, so there is no need to add the
setTracking function after lookToward.
Now that we have taken care of pointing at the Moon, we next want to
make time pass at an accelerated rate. Use the
setClockScale function for this. Add it to
the script by double-clicking on it in the Function Browser. The
Function Arguments panel contains a timestep spinbox for setting the
desired time step for the simulation clock. Change the timestep to
3 hours.
OK, we have pointed at the Moon and accelerated the clock. Now we just
want the script to wait for several seconds while the display tracks
on the Moon. Add the waitFor function to the
script, and use the Function Arguments panel to specify that it should
wait for 20 seconds before continuing.
To finish up, let us reset the clock's timestep to the normal value
of 1 second. Add another instance of setClockScale, and set its value
to 1 sec.
Actually, we are not quite done yet. We should probably make sure that
the display is using Equatorial coordinates before the script tracks
the Moon with an accelerated time step. Otherwise, if the display is
using Horizontal coordinates, it will rotate very quickly through
large angles as the Moon rises and sets. This can be very confusing,
and is avoided by setting the View Option
UseAltAz to false. To change
any View Option, use the changeViewOption
function. Add this function to the script, and examine the Function
Arguments panel. There is a combobox which contains the list of all
options which can be adjusted by changeViewOption. Since we know
we want the UseAltAz option, we could simply select it from the
combobox. However, the list is quite long, and there is no
explanation of what each item is for. It therefore may be easier to
press the Browse Tree button, which will open
a window containing a tree view of the available options, organized by
topic. In addition, each item has a short explanation of what the
option does, and the data type of the option's value. We find
UseAltAz under the Skymap options category.
Just highlight this item and press OK, and it
will be selected in the combobox of the Function Arguments panel.
Finally, make its value false or 0.
One more step: changing UseAltAz at the end of the script does us no
good; we need this to be changed before anything else happens. So,
make sure this function is highlighted in the Current Script box,
and press the Move Up button until it is the
first function.
Now that we have finished the script, we should save it to disk.
Press the Save Script button. This will first
open a window in which you can provide a name for the script, and fill
in your name as the author. Enter Tracking the Moon
for a name, and your name as the author, and press
OK. Next, you will see the standard &kde; Save
File dialog. Specify a filename for the script and press
OK to save the script. Note that if your
filename does not end with .kstars, this suffix
will be automatically attached. If you are curious, you can examine the
script file with any text editor.
Now that we have a completed script, we can run it in a couple of ways.
From a console prompt, you can simply execute the script as long as an
instance of KStars is currently running. Alternatively, you can execute
the script from within KStars using the Run
Script item in the File menu.
Device Automation with INDI
Device scheduling and automation is supported for all INDI-compliant devices. You can coordinate any number of devices to perform complex operations using &kstars; Script Builder. This can be accomplished by using &kstars; INDI DCOP interface, which provides different classes of functions to suit your tasks. The INDI DCOP functions can be decomposed into five different classes. The following is a review of the functions and their arguments as supported in KStars. It it highly recommended to read the INDI Concepts section as we will employ key INDI concepts throughout this tutorial.Generic Device Functions: Functions to establish/shutdown devices..etc.startINDI (TQString deviceName, bool useLocal) : Establish an INDI service either as local or server.shutdownINDI (TQString deviceName) : Shutdown the INDI service.switchINDI(TQString deviceName, bool turnOn) : Connect or Disconnect an INDI device.setINDIPort(TQString deviceName, TQString port) : Set the device's connection port.setINDIAction(TQString deviceName, TQString action) : Activate an INDI action. The action can be any element of a switch propertywaitForINDIAction(TQString deviceName, TQString action) : Pause script execution until the specified action property returns with OK status.Telescope Functions: Functions to control the telescope motion and status.setINDIScopeAction(TQString deviceName, TQString action) : Set the telescope mode or action. Available options are SLEW, TRACK, SYNC, PARK, and ABORT.setINDITargetCoord(TQString deviceName, double RA, double DEC) : Set the telescope JNow target coordinates to RA and DEC.setINDITargetName(TQString deviceName, TQString objectName) : Set the telescope JNow target coordinates to the coordinates of objectName. KStars will lookup the object name in its database and will fetch RA and Dec once found.setINDIGeoLocation(TQString deviceName, double
longitude, double latitude) : Set the telescope geographical
location to the longitude and latitude as specified. The longitude is measured
from Greenwich, UK, to the East. However, while it is common to use negative
longitudes for the Western hemisphere, INDI requires longitude values between
0 and 360 degrees. So if you have a negative longitude, simply add 360
degrees to get the value that INDI expects. For example, Calgary, Canada
coordinates in &kstars; are longitude: -114 04 58; latitude: 51 02 58. So
INDI's would need longitude = 360 - 114.083 = 245.917
degrees.setINDIUTC(TQString ddeviceName, TQString UTCDateTime) : Set the telescope UTC Date and Time in ISO 8601 format. The format is YYYY-MM-DDTHH:MM:SS (e.g. 2004-07-12T22:05:32).Camera/CCD Functions: Functions to control the camera/CCD properties and status.setINDICCDTemp(TQString deviceName, int temp) : Set the CCD chip target temperature in degrees celsius.setINDIFrameType(TQString deviceName, TQString type) : Set the CCD frame type. Available options are FRAME_LIGHT, FRAME_BIAS, FRAME_DARK, and FRAME_FLAT.startINDIExposure(TQString deviceName, int timeout) : Start the CCD/Camera exposure for the duration specified by timeout in seconds.Focuser Functions: Functions to control the focuser motion and status.setINDIFocusSpeed(TQString deviceName, TQString action) : Set the focuser speed. Available options are FOCUS_HALT, FOCUS_SLOW, FOCUS_MEDIUM, and FOCUS_FAST.setINDIFocusTimeout(TQString deviceName, int timeout) : Set the duration in seconds for any subsequent startINDIFocus operations.startINDIFocus(TQString deviceName, int focusDir) : Move the focuser either inward (focusDir = 0) or outward (focusDir = 1). The speed and duration of this operation is set by the setINDIFocusSpeed() and setINDIFocusTimeout() functions.Filter Functions: Functions to control the filter position.setINDIFilterNum(TQString deviceName, int filter_num) : Change the filter position to filter_num. The user can assign aliases to filter numbers in the Configure INDI dialog box under the Devices menu (e.g. Filter 1 = Red, Filter 2 = Green..etc).
Note that the device name is the first argument of all INDI functions. This permits different commands that are sent to different INDI devices to be intermixed together in one script. The Script Builder tool provides two options to facilitate the creation and editing of INDI scripts: : When checked, the Script Builder tool will automatically add waitForINDIAction() after any action it recognizes. For example, If you add switchINDI() function to the script and this option was checked, the Script Builder will add "waitForINDIAction CONNECTION" in the script file just after switchINDI(). This will cause the script to pause after it issues switchINDI() until switchINDI() returns with OK status (&ie; device connection was successful). It is critically important to know that the Script Builder cannot automatically add waitForINDIAction() for generic actions added using the setINDIAction() function. This is because KStars cannot determine the parent property of generic actions. Therefore, you must manually add waitForINDIAction() after generic actions when desired. : When checked, the device name field of all subsequent functions is automatically filled with the last device name. The last device name is set every time startINDI() function is added to the current script. When working with multiple devices, it is recommended to have this option off.Now we are ready to create a demo script that controls LX200 GPS telescope, in addition to Finger Lakes CCD camera. Our task is simple. We will ask the telescope to slew and track Mars, then we will ask the camera to take three shots 10 seconds each separated by 20 seconds.Since there is no direct feedback from the INDI DCOP interface about the progress, value, or status of the device operations and parameters (except for waitForINDIAction()), device automation in KStars is similar to an open-loop control system. In such a system, there is usually no direct feedback to measure the progress of the system and to correct for errors. Consequently, you must design your device automation scripts with careful consideration. All automation scripts must be subjected to rigorous testing before deployment.
The Script Builder Tool
Script Builder ToolThe demo script is shown in the above screenshot. Note that we checked and unchecked . The first function to add is startINDI() as shown above. We want to run our devices as local, so we will not change the service mode provided in the function arguments window. We type in our device name, starting with the telescope "LX200 GPS". We repeat the same operation again for "FLI CCD". There is a waitFor() function after that. It is generally recommended to use waitFor() function immediately after startINDI() to pause the script for 1-5 seconds. This will ensure that all properties are built and are ready to receive command. It is also useful for controlling remote devices because retrieving and building properties might take some time. In the next function, switchINDI(), we connect to each device.Since is checked, we do not need to add waitForINDIAction() after switchINDI() to insure that we only continue executing the script after we successfully connect. This is because the Script Builder tool will do this automatically for us when we save the script. Now let us set the telescope mode to tracking, click on the setINDIScopeAction() function and select TRACK. Note that we need to set the telescope to tracking before issuing the coordinates it needs to track. The setINDIScopeAction() function is provided for convenience; since in this example, it simply issues a generic setINDIAction() function followed by the keyword TRACK. However, the benefit of using setINDIScopeAction() is that KStars can automatically append waitForINDIAction() after it when required. This facility is not automatically available to generic actions as we discussed before.Next we use the setINDITargetName() function and set it to Mars. Finally, the last few steps involve capturing an image for 10 seconds which can be done by using startINDIExposure() function, and waiting for 20 seconds in between which can be done by using waitFor() function with a value of 20.We can now save our script and execute it at any time. The saved script will be similar to this:
The INDI Library provides robust scripting tools that enable developers to orchestrate very complex scripts. For more details, refer to the INDI Developer Manual.