Setting up a pyobs system with simulated telescope and camera

Note

This recipe requires three accounts on your XMPP server (see Setting up ejabberd): telescope, camera, and gui.

Setting up the venv

For this recipe, we start with a fresh new virtual environment in a new directory of your choice and install pyobs-core and pyobs-gui:

cd /path/to/test
python3 -m venv venv
source venv/bin/activate
pip install pyobs-core pyobs-gui

Remember that in every new terminal you need to activate the venv first:

cd /path/to/test
source venv/bin/activate

Simulated telescope

pyobs contains classes for simulated telescopes and cameras, called DummyCamera and DummyTelescope, respectively.

Starting with the telescope, create a file telescope.yaml with the following content:

{include _environment.yaml}

class: pyobs.modules.telescope.DummyTelescope

comm:
    class: pyobs.comm.xmpp.XmppComm
    jid: telescope@localhost
    password: pyobs

With the class keyword we define the previously mentioned class for the dummy telescope. For communicating with other modules, it also needs a Comm object, which we define under comm.

Note

For the Comm configurations given in this recipe, remember to adjust JIDs and passwords according to your setup.

Since the location for all modules will be the same, we outsourced it into a file _environment.yaml, which is included in the first line, and has the following content (for this example, this is the location of the SAAO in Sutherland, South Africa):

timezone: Africa/Johannesburg
location:
    longitude: 20.810808
    latitude: -32.375823
    elevation: 1798.

You can now simply run the configuration by calling pyobs telescope.yaml. The last line of the produced output should contain Started successfully. You can shutdown the module via Ctrl-c.

Simulated camera

Open a new terminal and activate the venv. Then create a new file camera.yaml with the following content:

{include _environment.yaml}

class: pyobs.modules.camera.DummyCamera

comm:
    class: pyobs.comm.xmpp.XmppComm
    jid: camera@localhost
    password: pyobs

Again, start the module via pyobs camera.yaml. Congratulations, you have set up your first pyobs system!

Graphical user interface

In order to get a graphical user interface (GUI) to the system, we can employ the pyobs-gui package. Again, open a new terminal and activate the venv. Then create a file callen gui.yaml:

{include _environment.yaml}

class: pyobs_gui.GUI

comm:
    class: pyobs.comm.xmpp.XmppComm
    jid: gui@localhost
    password: pyobs

Start the module (pyobs gui.yaml) and you should see a window open with two entries on the left side for telescope and camera. Clicking on those will give you controls to move the telescope and take images with the camera.

Virtual file system

Now, while most buttons should work nicely, when taking an image you will get an error message like this:

ValueError: Could not find root cache for file.

This happens, because pyobs does not now where to store your images.

For this to work, we need to add a vfs for both camera and gui, i.e. the two modules that need to access the files. Simply add the following to both configuration files:

vfs:
    class: pyobs.vfs.VirtualFileSystem
    roots:
        cache:
            class: pyobs.vfs.LocalFile
            root: .

Restart both modules and take an image. You will see that the GUI now shows it to you after the exposure is finished.

Connecting telescope and camera

When you look of the FITS headers of the taken images, you see that they contain entries that were automatically added from the telescope module, like TEL-RA and TEL-DEC, but these keywords are only added after the image has been taken. During the exposure, the simulated camera does not now where the simulated telescope is looking at.

A convenient way to solve this is to run both modules in a shared process via a MultiModule and have a shared object for the simulation. Shut down the two modules for telescope and camera and create new file telcam.yaml:

{include _environment.yaml}

class: pyobs.modules.MultiModule

shared:
    world:
        class: pyobs.utils.simulation.SimWorld
        time: "2020-10-21 22:00:00"

        telescope:
            class: pyobs.utils.simulation.SimTelescope

        camera:
            class: pyobs.utils.simulation.SimCamera

modules:
    camera:
        class: pyobs.modules.camera.DummyCamera
        comm:
            class: pyobs.comm.xmpp.XmppComm
            jid: camera@localhost
            password: pyobs
        vfs:
            class: pyobs.vfs.VirtualFileSystem
            roots:
                cache:
                    class: pyobs.vfs.LocalFile
                    root: .

    telescope:
        class: pyobs.modules.telescope.DummyTelescope
        comm:
            class: pyobs.comm.xmpp.XmppComm
            jid: telescope@localhost
            password: pyobs

As you can see, this configuration contains exact copies of the previously separate configurations for camera and telescope, but now as entries in the modules dictionary.

If you look at the constructors for DummyCamera and DummyTelescope, you will see that they both accept a SimWorld object called world. And this is exactly what we provide in the shared dictionary. As you can see, we can also add parameters for the simulation like the time.

If you start this multi-module via pyobs telcam.yaml, you will again see two modules in the GUI, but now you will get a simulated star field according to the position of the telescope.