Guide to observing remotely with ALFOSC

This page contains specific instructions for the NEON summer school 2011.

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 `skype' connection. If not available or nobody is in the control room (e.g., in the daytime) please call the control room (+34-922405660) or 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 terminal on your computer

This is only possible from computers with a previously registered IP number.

You will be prompted for a password which will be supplied by the NOT staff.

Starting the control software

Once logged in to tessa (in the above mentioned terminal) type
startobssys remotealfosc
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 remotealfosc' command will open a total of 8 windows (see picture here):
- 2 `sequencer' terminals (6) and (7)
- A CCD status windows (1)
- The ALFOSC instrument status display (3)
- The ALFOSC instrument control (2)
- the TCS status display (4)
- a `Talker' window which provides status, warning and error message for the observing system (5).
- a small `tech-xterm' window in which the low-level communication messages with the instrument can be seen. This window can be `minimized' (8).
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 tessa.

Starting the postprocessing image display

Open a terminal on your computer

This is only possible from computers with a previously registered IP number.

You will be prompted for a password which will be supplied by the NOT staff.

In the terminal window a line of text similar to this will appear:
setdisplay 'localhost:18.0'

Copy and paste that line into the ALFOSC sequencer terminal

Type in the ALFOSC sequencer terminal
display-start
An empty DS9 window should appear. HAVE PATIENCE. This may take some time.
ALFOSC FITS images will be displayed in the DS9 window automatically after they have been saved.

For best results, choose the 'Scale' option 'zscale' in the DS9 display.
In the second sequencer terminal, type
alfosc.imexam
which will display a graphics window (HAVE PATIENCE) and put the cursor in imexam mode on the image loaded into the DS9 window. As new images gets loaded into the DS9, the imexam task will automatically work on these, so there is no reason to quit the imexam task after every analysis.

Accessing data

The data taken can be retrieved with 'ftp' from the computer ftp.not.iac.es.

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.calibexp	to make a spectroscopic lamp calibration
alfosc.wheels	to set all wheels on the command line
alfosc.imexam	to start an IRAF 'imexamine' session on the displayed image
alfosc.teloffset	to offset the object relative to CCD
alfosc.??????

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/.
For the NEON summer school use the proposal number 43-703.

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 43_703_<catalogue-name>.cat
where <catalogue-name> is the specific name you have given the catalogue.

Start of the night

Note that for this summer school the NOT staff will take twilight flat fields at the start of the night, after which the remote observers are expected to start-up the system and focus the telescope. This will be around UT 21:00-21:15. Moletai local time is UT+3h!

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

At the start of the night the following commands should be executed.

To set-up the telescope for use with ALFOSC type in any sequencer window
tcs.setup-tel-alfosc

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.goto-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.find-object <my-object-name>
tcs.preset-with-parallactic-angle-to-selected
where <my-object-name> is the name of the target in the TCS catalog

Assessing 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.

Focussing the telescope

Very important: Quit any active imexam sessions prior to running this task

Note that no abbreviated commands can be used in the remoteobssys and commands should be used with the proper system prefix and full name. E.g., `foc-pos' should be written as `tcs.focus-position'

Set the focus to the default value for ALFOSC by typing foc-pos 23300 on the TCS. This is also done by the script tcs.setup-tel-alfosc. The value for foc-del (which needs to be set when using a filter) is automatically set to zero when setting foc-pos.

Load the Landolt fields catalogue that can be use for focussing with the command tcs.read-catalogue alphot.cat. The catalogue list can be seen here.

Point the telescope to a focus field.

Setup ALFOSC for focusing with the focus pyramid:
- Take out any filters from the light beam in case you want to measure the foc-pos value.
  Otherwise, for measuring the foc-del value, put in the desired filter.
- Set the aperture wheel to the Open position.
- From the grism menu, choose Focus Pyr.
- To speed up things make a smaller window on the CCD by typing focuswindow in the sequencer window.

Take an exposure (of at least 10 seconds) by typing, e.g., expose 12 in the sequencer window. For the focus fields typical exposure times are 10 seconds without a filter. In case the filter offset has to be measured, 15-30 seconds for broad band filters, and significantly longer exposure times for narrow band filters are required. The focus image will be shown in the DS9 window.

Type focuspyr-auto in a sequencer window. The focus pyramid images will be analyzed automatically, and the calculated telescope focus offset will be displayed in the talker and sequencer windows. If you wish to analyse the focus pyramid image interactively, do the following step:

Type focuspyr in a sequencer window. (This will automatically run focuspyr-auto in the image as well so offsets can be compared). Put the cursor on the upper one of the four images of one focus star in the display. Type a followed by q to measure the focus offset. Repeat this sequence on several stars to get a better estimate of the offset. With the cursor in the DS9 display, type q to escape from the focus measurement mode. The number of steps to move the telescope focus will be shown.

Change telescope focus by typing foc-pos <new-value> on the TCS, or tcs.focus-position <new-value> in the sequencer.

Repeat the focusing procedure at least once until a stable focus has been found.

When finished:
- Move the focus pyramid out of the beam.
- Reset the CCD readout window and binning to the desired size. To obtain full frame window without binning, type resetxy in the sequencer window .

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

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 follow the procedure given here.
To speed-up the procedure we suggest you window the CCD by executing the focuswindow script in the sequencer window at the start.
Very important: Quit any active imexam sessions prior to running the `slitoff' task

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 tessa
shutdownobssys remotealfosc
and wait a little while. You can use the 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 remotealfosc observing system when you are not using it!

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

Last modified: 20-Jul-2011