Guide to observing remotely with ALFOSC - using VNC

This page only describes things that are special for the remote observing procedure. All things related to observing with ALFOSC are documented on the main ALFOSC web pages.

Communication

In case of any doubts or questions, please contact the control room directly using the zoom connection. If it's not available, Control Room's phone is +34-922405660 or 661.
If there's no one in the Control Room, contact the Service Building (+34-922405663).

Preparations

There are various things that can/should be done in preparation for the observations. For each target:

the required exposure time can be estimated here

the visibility during the night should be check, e.g., here

and finding charts can be prepared here (ING DSS) or here (Aladin)

Make sure that the telescope staff knows the needed instrument setup and calibrations.

With all this information it is now possible to draw up an observing plan, defining the order in which you want to observe your target with approximate time-line for the observations. For this you should take in to account the time it takes to position a target, for instance onto a slit (see http://www.not.iac.es/observing/tools/overheads.html). It also is good to define priorities for the different targets. Together with the time-line this will make it easier to decide what to do in case the observations do not proceed as fast as expected, or if the weather changes. It also is good to have some back-up targets in case the observations proceed faster than expected, or if, e.g., some of the main targets can not be observed due to strong wind from the wrong direction.

Logging in

Open a VNC client on your computer. We're using VNC4 (based on RealVNC) for the server, so the recommended client is "xvnc4viewer" (that's the package if you need to install it on Linux). Any viewer will work, though.
Open a remote desktop on lisa.not.iac.es, port 5913. On Linux this could be done like this:
```
      $ vncviewer lisa.not.iac.es:5913
```
NB1: access to lisa is only possible from computers with a previously registered IP number.

If you are prompted for a user and password which will be supplied by the NOT staff.

It may be that the support at the telescope asks you to switch your VNC viewer to "non interactive" or "view only" mode. Your client may support switching this off (typically, push F8 and look for some option that let's you disable the mouse/keyboard input). If that's not the case, simply close the window and open it again like this:

      $ vncviewer -viewonly lisa.not.iac.es:5913

That way you may be able to follow what the other side is doing, without accidentally interfering.

NB: In the documentation it may ask you to use -ViewOnly (capitalized). In principle, the capitalization shouldn't matter.

Starting the control software

Once logged in to selena, open a terminal type if there's not one, and type
startobssys vncalfosc
then type the TCS access-code when prompted. The TCS access-code changes every day at noon UT. For this reason the observing system needs to be restarted every day and the TCS access-code should be obtained in advance from the NOT staff on La Palma (see above for contact information).
In case there is already a ALFOSC observing session running this command will fail. Contact the telescope to resolve this.
The `startobssys vncalfosc' command will open a number of program windows. Refer to ALFOSC's Cookbook for an example.
The command takes some time to startup and depending on the connection it will take some time for all windows to appear.
To operate the system, commands can be typed in the two sequencer terminals.
To close a sequencer terminal type 'exit' at its prompt. You can always get another sequencer terminal, using the command 'seqterm'. This is possible from any sequencer terminal window as well as any other terminal window logged in on selena.

Accessing data

Read more instructions about it in here

Observing with ALFOSC

Target and/or (daytime) calibration observation can now been made with ALFOSC through commands in the ALFOSC sequencer windows.

Observing with ALFOSC and use of the sequencer system is described in detail on the ALFOSC web pages

Some often-used commands:

alfosc.expose	to make an exposure
alfosc.dark	to make a dark/bias
alfosc.bin	set CCD binning
alfosc.xbeg	set CCD window
alfosc.ybeg	set CCD window
alfosc.xsize	set CCD window
alfosc.ysize	set CCD window
alfosc.resetxy	to reset CCD parameters
alfosc.object	to set the OBJECT header
alfosc.imexam	to start an IRAF 'imexamine' session on the displayed image
alfosc.teloffset	to offset the object relative to CCD

Documentation of ALFOSC/telescope Sequencer commands and scripts

Target catalogue

To be able to point the telescope to your targets you need to prepare a catalogue with the coordinates. Instruction and a web form to enter the target coordinates can be found at http://www.not.iac.es/observing/forms/catalog/.

After generating the catalogue you need to read it in to the observing system. To do this, type in any sequencer window
tcs.read-catalogue 52_702_<catalogue-name>.cat
where <catalogue-name> is the specific name you have given the catalogue.

Start of the night

Note that for this school the NOT staff will take twilight flat fields and focus the telescope at the start of the night, after which the remote observers are expected to start-up the system and and start observing. This will be around UT 19:50. Remember that the local time in Stockholm UT+2h (summer time).

Around sunset the local staff will power-on the telescope, open the hatches and side ports (depending on the weather conditions).

At this time also the `skype' connection should be tested, which requires somebody to be present at both ends of the connection.

Setup the telescope

To set-up the telescope at the start of the night, and after every switch from another instrument (e.g. from FIES), the following commands should be executed in any sequencer window
tcs.setup-tel-alfosc

The above command sets the telescope focus to the default value, so you may want to set it to the value found in the beginning of the night (ask control room if you don't know):
tcs.focus-position 23xxx

Spectroscopy: Define the parallactic angle

At every switch from horizontal to vertical slit (and vice-versa) one of the following commands should be executed.

For spectroscopy with horizontal slits, define the parallactic angle with
tcs.instrument-parallactic-angle 0

For spectroscopy with vertical slits, define the parallactic angle with
tcs.instrument-parallactic-angle 90

Moving the telescope to a target

Select the target that you want to observe

Switch off autoguiding:
tcs.ag-off

For safety reasons, always contact the NOT staff at the telescope before moving to make sure it is safe to move

IMAGING: To move the telescope to the object, type in the sequencer window the command
tcs.guide-object <my-object-name>
where <my-object-name> is the name of the target in the TCS catalog

SPECTROSCOPY: First make sure that the parallactic angle is defined correctly (see above).
To move the telescope to the object, type in any sequencer window the commands
tcs.guide-object-with-parallactic <my-object-name>
where <my-object-name> is the name of the target in the TCS catalog

Access to the data log

You can keep an eye of recorded images during the night (an 'obslog') by producing an End-of-Night report already at the start of the night and reload the content when needed:

Access the EON report form http://www.not.iac.es/observing/forms/eon/, providing the proposal number and date as requested.

Do not fill in any information at this stage, just submit the EON form.

Follow the URL displayed to view the online EON report. The online report includes an up-to-date listing of all images taken that night.

Refresh the page as often as required to update the image listing. The full URL of the page is unique and the only way of accessing the report. Do not loose it.

Assessing the data with the postprocessing system

Spectroscopic data will automatically be reduced by the quickspec postprocessing script which will show the reduced spectrum in a dedicated graphics window.
This script can also be run from the the ALFOSC sequencer terminal with
alfosc.quickspec

Furthermore, any frame that is saved to disk will be displayed in the postprocessing display. If the imexam task is active on the 2nd sequencer window, you can obtain obtain plots, statistics, etc. using the imexam facilities immediately. Alternatively, use imexamin in IRAF on your downloaded image locally.
For the focussing and slit-acquisition procedures described below the postprocessing display will allow you to interactively point at your targets (stars/galaxies/etc.) during the procedure.

Imaging: Filter focus offsets

When inserting an imaging filter or spectroscopic order-blocking filter in the beam, the telescope focus might need a correction.
Follow the procedure described on this page.

Spectroscopy: Setting the slit angle (to get 2 objects on the slit)

See for a description and/or follow the procedure described on this ALFOSC page.
Very important: Quit any active imexam sessions prior to running the SLITROT task

Imaging: Setting North-is-up

If the field rotation is changed, e.g., to orient a slit along 2 object (see here), the following command should be executed.

To set North-is-up on the CCD, set the rotator angle with
tcs.field-rotation 90

Spectroscopy: Centering the target on a slit

To position a star on the slit use the acquisition script
alfosc.acquisition [-c] [-q] <slit-specifier> <exptime>

Note: the slit specifier should be a unique string. A list of optical items can be found here.

Example:
alfosc.acquisition Slit_1.0 10

Web camera view of the NOT control room

A web page that will show an web camera image of the NOT control room is provided. It is updated every 3 seconds. The NOT staff will control where it points. The page is accessed here.

The page is password protected. The username and password can be obtained from the NOT staff.

Shutting down

Each student group is expected to shutdown the observing system at the end of their session.

To shut down the instrument software, type in a terminal window logged in on selena
shutdownobssys vncalfosc
and wait a little while. You can type this in the same terminal window you used for starting the software.
Note that you can operate both the instrument and the telescope from the remote observing system. To avoid any problem always shut down the vncalfosc observing system when you are not using it!

Log out from the desktop session

As the final step, fill out the EON report, now with all details.

Last modified: April 19 2023