Text Size:
Smaller Text Normal Text Larger Text


Follow us on Twitter

Guide to observing remotely with NOTCam

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


  • 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).


  • There are various things that can/should be done in preparation for the observations (see NOTCam Cookbook, first section). For each target:
  • At this time one should also consider what kind of calibration is needed for the data, specifically if apart from day-time calibration, night time calibrations are needed.

  • 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 acquire a target (for NOTCam imaging typically 3 minutes). It is also 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
  • Log in to the computer at the telescope using the following command

       ssh -X

  • 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 marissa (in the above mentioned terminal) type

       startobssys remotenotcam

    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 NOTCam observing session running this command will fail. Contact the telescope to resolve this.

    The `startobssys remotenotcam' command will open a total of 8 windows (see picture here):

    • 2 `sequencer' terminals (6) and (7)
    • A detector status windows (1)
    • The NOTCam instrument status display (3)
    • The NOTCam 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 marissa.

Starting the postprocessing image display

  • Open a terminal on your computer
  • Log in to the computer at the telescope using the following command

       ssh -X

  • 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:

       notcam.setdisplay 'localhost:18.0'

  • Copy and paste that line into the NOTCAM sequencer terminal
  • Type in the NOTCAM sequencer terminal


    An empty DS9 window should appear. HAVE PATIENCE. This may take some time.
    NOTCAM 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


    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.

Observing with NOTCam

  • Target and calibration observations can be made with NOTCam through commands in the NOTCam sequencer window. Go to your working directory by typing cd ~obs/scripts/45-701, where 45-701 is the project number given for the actual school. If you made pointing scripts they will be located here.
  • Observing with NOTCam and use of the sequencer system is described in detail in the NOTCam CookBook.
    The lists of NOTCam Sequencer commands and NOTCam Sequencer scripts are given for reference, overview and description.
    Note that the prefixes ''notcam.'' and ''tcs.'' are needed inside scripts but not on the command line in the NOTCam sequencer window.

    For more details regarding NOTCam in general, as well as data reduction using the quick-look IRAF pacakge, we refer to the NOTCam User's Guide.

  • Note 1: If the detector has been idle for a while or saturation has occured it is a good idea to ''clean'' it using the command notcam.clear, or alternatively run the script notcam.clean3 which makes 3 clear commands and one notcam.dark 0 to display the result of the cleaning.

    Note 2: If you need to interrupt an integration, use Ctrl-C on the command line, but note that it will only interrupt the script, not the ongoing exposure. You will have to wait until the current exposure finishes. This is particular for NOTCam, which does not have a functioning abort command.

Accessing data

  • The data taken can be retrieved with 'ftp' from the computer
  • Read more instructions about it in here


  • 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 Alternatively, you can make pointing scripts for each target.
  • After generating the catalogue you need to read it in to the observing system. To do this, type in any sequencer window /catalogue/43-702_<catalogue-name>.cat

    where <catalogue-name> is the specific name you have given the catalogue (and 43-702 refers to the proposal ID, in this case for this summer school).

Start of the night

  • Around/before sunset the local staff will power-on the telescope, open the hatches and side ports (depending on the weather conditions), load the catalogue (if not already loaded before) for the remote observation in to the TCS, and startup a program that will monitor the instruments during remote observing.

    In the case of this summer school, local staff will take afternoon calibrations and evening twilight flats as requested by the observers. They will also focus the telescope. Then the telescope will be handed over for remote observing. Note that Stockholm local time is UT + 2h.

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

Setup telescope

  • To set-up the telescope for use with NOTCam, type at the start of the night in any sequencer window


  • NB! This is not needed for this summer school, since the telescope will already be setup for NOTCam and focusing has already been made. Re-running this script will set the focus back to the default value rather than the actual focus value found for tonight.

  • and set the guide star positioning to fully automatic:

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, 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.

Moving the telescope to a target

  • Select the target that you want to observe. You may also enter an object directly through the sequencer window:

       tcs.enter-object <my-object-name> <hh> <mm> <ss.s> <dd> <mm> <ss.s> <epoch> <pm-ra> <pm-dec> <mag>
       Example: tcs.enter-object AS26 13 41 45.4 28 29 50.0 2000.0 0.0 0.0 11.4

  • Switch off autoguiding before moving to a new target:

  • For safety reasons, always contact the NOT staff at the telescope before moving to make sure it is safe to move.
    To move the telescope to the object, type in any sequencer window the command <my-object-name>

    where <my-object-name> is the name of the target in the TCS catalog.

  • If you dither more than 60'' from initial pointing or if you use beam-switching, then you need to acquire your guide star in a specific guide area using the "get-guide-star (g-g-s)" command. When the telescope has arrived at your target, proceed as follows:

       tcs.tcs-command "g-g-s 1 NOTCAM-Re"     or
       tcs.tcs-command "g-g-s 1 NOTCAM-S-posX"     or
       tcs.tcs-command "g-g-s 1 NOTCAM-N-negX"     or
       tcs.tcs-command "g-g-s 1 NOTCAM-E-negY"     or
       tcs.tcs-command "g-g-s 1 NOTCAM-W-posY"     or
       tcs.tcs-command "g-g-s 1 NOTCAM-Be-NS"     or
       tcs.tcs-command "g-g-s 1 NOTCAM-Be-EW"

    Make sure you are autoguiding with a proper signal and that your specific guide area selection is used before continuing. This can be seen on the TCS status display.

    If your maximum dither is 60'' or less the default guide area (NOTCAM-De) is fine.

NOTCam focusing for imaging mode

    For the Stockholm 2012 school the focus for the WF camera and K-band filter will be already found and set by local staff in the beginning of each night.

    The default NOTCam focus is the focus for the WF camera and the Ks band and currently has the value 22410. The actual focus value may change by up to 100 units and should be determined every night. Any offsets from this value required for different filters and/or cameras will be taken care of automatically by the notcam.setup-ima script. If you wish to determine the focus, or re-check it because the seeing has improved, or because you are changing to the HR camera, then do as follows:

  • Setup the instrument for focusing (puts in the focus pyramid and sets filter to Ks) and selects the camera lens (WF or HR), corresponding internal focus and whether to use the small mask in the aperture wheel or not:

       notcam.setup-focpyr camera
        Example: notcam.setup-focpyr WF

  • Use your target or go to a standard star. Take an exposure of at least 15 s.

       notcam.expose 15

  • Move the telescope about 15'' in any direction to be able to subtract sky.

       notcam.teloffset 0 15

  • Set sky subtraction to use this first image. Then take another exposure.

       notcam.setskysub image-name
       notcam.expose 15

  • Determine the offset from the best focus, manually or automatically, or both.


    The value that comes out is the offset from the actual focus position. You must add this number to the current focus value to get the new focus value.

  • Set the new telescope focus value,

       tcs.focus-position new-focus-value

    and iterate at least once. Remember to take out the focus pyramid. This is done automatically if you run the setup-ima script as explained in the next point.

NOTCam imaging

  • Already while the telescope is moving, you can make sure you have the correct camera and filter setup for NOTCam. If you can not simply click on the instrument display (because of a slow connection), you may run the setup script:

       notcam.setup-ima cam filter
       Example: notcam.setup-ima WF 207

    where cam and filter are the camera and filter selections. The choices for cam are WF or HR. The internal focus and the mask in the aperture wheel is set accordingly. To specify filter you must use the NOTCam filter ID number (201-237). J = 201, H = 203, Ks = 207, Y = 236.
    NB! Since Feb-2010 this script corrects internally the filter and camera focus offsets by applying the tcs.focus-delta values listed in the focus offset table. Make sure that the focus-position value is always for WF camera and Ks band.

  • Take a test exposure to check positioning of target, measure seeing and peak values, background level etc. in order to fine-tune exposure times.

       notcam.expose t
       notcam.frames t N

    where t is the exposure time in seconds for the reset-read-read mode (expose), while for the ramp-sampling mode (frames) the parameters t and N are the time (in seconds) between each of the N non-destructive readouts (giving a total exposure time of t*N).

  • In order to see your target you may have to subtract the background. To do this move the target for instance 10 arc seconds and take another image.

       notcam.teloffset x y

    where x and y indicate the direction by which the target moves on the array, the amount being in arc seconds.

  • Set the display mode to use the N'th previous image for sky subtraction:

       notcam.setskysub N

    where N normally is 1 to use the previous image. Take another image with the same exposure mode and time as above. Note that it is usually useful to have the skysub set to previous image during normal NOTCam observing, but you can toggle it off at any time by typing: notcam.setskysub no in one of the sequencer terminals.

  • Check your seeing and peak values (to avoid exceeding the linear range at about 25000 adu for targets, and avoid saturation at about 54000 adu for any object) using the imexam task which should always be active from the 2nd sequencer window. Alternatively, use imexamin in IRAF on your downloaded image locally.

    Note that there is some postprocessing information available as SExtractor results for each image. If you set notcam.overlay yes this info, such as seeing (in arc seconds) and sky background level (in ADUs) is overlaid on the displayed image. NB! Note that the background level is the level on the potentially sky-subtracted image! Saturated stars (and hot pixels) are marked with red circles.
    Note that the SExtractor parameters such as background level and seeing values may not work well on NOTCam images and can not be fully trusted.

  • When you are satisfied with the location of your target on the array and have checked peak values to fine-tune exposure parameters in your script myscript, you may start your script by typing:


    in the sequencer window. Note that it must be executable. An alternative way of observing is to use the already existing NOTCam sequencer scripts, such as for instance:

       notcam.5point rmode t N obj step skew Ncycles
       Example: notcam.5point exp 10 1 AS26 15 0 2
       Note that if rmode=exp then the script will ignore the value of N. No skewed grid in the above example. The dither is repeated twice.

       notcam.9point rmode t N obj step skew Ncycles
       Example: notcam.9point frame 10 7 GRB 10 3 1
       Here the 3x3 grid with a dither step size of 10'' will be skewed by 3''. Exposure time is 70s per dither position. No repetition of cycle.

       notcam.beamswitch rmode t N obj dir beam step skew
       Example: notcam.beamswitch frame 5 10 nebula W-posY 240 10 3
       Beamswitch offset = 240'' to the west. Both ON and OFF positions mapped in a 3x3 grid with a dither step size of 10'' skewed by 3''. Note that the notion "W" (west) refers to the telescope movement and is valid only for the default rotator position (field-r -90), while "posY" refers to the direction the star(!) moves on the array and is always valid.

    where rmode is the exposure mode (exp, mexp or frame), t and N being the exposure mode parameters, obj being the object name, step being the dither step size (in arc seconds), skew being the additional offset to provide a skewed dither grid (in arc seconds), Ncycles the number of times to repeat the dither pattern (default = 1), dir being the direction on the sky to move out for beamswitch mode (S-posX,N-negX,E-negY,W-posY), and beam being the beamswitch offset size (in arc seconds). Make sure you use the corresponding guide area.

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

    For the Turku school, 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 marissa

       shutdownobssys remotenotcam

    and wait a little while.

    Note that you can operate both the instrument and the telescope from the remote observing system. To avoid any problem always shut down the remotenotcam observing system when you are not using it!

  • As the final step, fill out the EON report, now with all details.
Back to top Last modified: 17-Oct-2013