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StanCam Cookbook

Last updated October 07 2023
Please refer to the online version for the latest update

Table of Contents

Preparing Observations

Observing scripts

Observing scripts can be generated automatically through the Observing Script Generator or crafted manually. If done through the web, the script will be uploaded and within a few minutes available in ~obs/scripts/proposal-ID, where proposal-ID refers to the proposal ID entered in the web form (e.g. 38-042). If the directory does no exist, it will be created. If you make your observing scripts manually, first make the proposal ID directory (using mkdir) and place them therein.

The scripts are executed from the sequencer window, from the directory where they are placed. Note that if you are saving scripts or files elsewhere in the ~obs account, the directory will be cleaned up after every run and it will not be possible to recover them.

Create a TCS Target Catalogue

A source catalogue can be made well in advance of your observations by using the web interface, NOT Source Catalogue Creation. Note that it is also possible to enter targets on-the-fly and create a catalogue directly on the TCS while observing (See section, Loading Target Catalogue).

Exposure Time Calculator

The Exposure Time Calculator can be used to estimate the required exposure times for ALFOSC, NOTCam, FIES, MOSCA and StanCam (both in imaging and spectroscopy mode, where it is available).

StanCam filters

StanCam filter cassette has nine slots and the nominal time to change filter is 30 seconds. However, when having short integration times with full frame and altering two adjacent filters the time resolution is about 64 seconds, (integrating 2 seconds, reading out the full frame 44 seconds and changing filter 18 seconds).

Note, while SOFIN is mounted the red light from SOFIN makes SDSS z-filter imaging virtually impossible.

StanCam detector, CCD1

The CCD1 is linear (better than 0.2%) up to digital saturation (216ADU) and the typical bias level is about 340ADU.

StanCam read out time

The read out time of the full frame is 43 seconds. The readout time can be reduced either by binning or windowing.

Afternoon Preparations

Overview of everyday afternoon tasks

  • Update the TCS target catalog if necessary, and upload it to the TCS.
  • Find out the TCS access code of the day on TCS status page 1
  • Shutdown the STANCAM Sequencer:
    [obs@tessa]$ shutdownobssys stancam
  • Kill all remaining windows on the lisa display
  • Startup the STANCAM Sequencer
  • In all STANCAM Sequencer windows change the working directory to the one assigned to your program, for instance
    [obs@tessa][STANCAM]$ cd ~obs/scripts/38-025
  • Edit and test your scripts.
  • Take calibration frames.

TCS access code

Any instrument computer which needs access to the TCS, for instance to move the telescope during slit acquisition or dithering, will ask for the current TCS access code at start-up. This code is updated every day (around lunch time). When you are asked to supply the TCS access code, do the following:

  • On the TCS VT510 terminal, make sure that the brightness is turned up
  • On TCS type: Show-Page and then 1 (or type sh-p 1 for short)
  • The TCS access code is shown on the top part of the screen as: AccessCode xxxxxxxxxx

Starting the StanCam observing system

  1. On the Chooser click on the line
    ' Willing to manage'
  2. Log in with username 'obs'. Password is the standard one.
  3. In a terminal window type
    [obs@tessa~]$ startobssys stancam
    A window will pop-up, asking for the TCS access code. Type it and press enter. I you type the wrong code the line will be cleared and you must try again.

    All the STANCAM software will now be started - the BIAS programme, a window showing relevant TCS information and the postprocessing control. You will notice two new things, namely an X-terminal in blue colors with the title "STANCAM Seq" and a log program called the Talker (the lisa-screen should look like this this ).

    Do not close this window.

    The X-terminal (also called "seqterm". Use this command to get another sequencer terminal) is used to type in the sequencer commands. The Talker is used to watch and control the execution of the sequencer commands. Also be aware the IT IS NOT POSSIBLE TO TYPE ANY COMMANDS IN THE BIAS "COMMAND" WINDOW.

    Wait until the UT clock in the first line in the BIAS Status window starts to run.
    The data will be saved in /data/stancam and will have the format STph160001.fits, where 'ST' is the image prefix for STANCAM images, 'ph' is for 2006/August, '16' is for the date 16 in the month and '0001' is a running number.

  4. In an STANCAM SEQUENCER window set the OBSERVER FITS header to hold the name of the actual observer(s):
    [obs@tessa][stancam]$ observer "Your Name"
    This will remove the RED "no-observer-specified" alert in the small "STANCAM Run Selector" window, and will show the new value of the OBSERVER FITS header nicely in GREEN instead.

  5. The automatic StanCam observing log displays a listing of FITS headers for incoming data files. The System Talker lists incoming messages from the Sequencer. These two programs are displayed on the InfoSys monitor, and are automatically reset every afternoon. If you change between instruments you can change the obslog with the command e.g.:
    [obs@marissa][STANCAM]$ stancam.showlog

  6. The default StanCam start-up marks the FIES fibres positions on every image displayed. If you wish not to mark the fibres give a command fibmark no.

  7. Use and enjoy the Sequencer.

Loading the TCS Target Catalogue

  • On the TCS, press the catalogue button CAT to view the object catalogue. If you want to erase the current catalogue that is displayed, type erase-catalogue on the TCS.
  • Load a source catalogue by typing read-catalogue on the TCS, where catname is the name of the catalogue. A source catalogue can be created by using the web interface or the objects can be added directly to the current TCS catalogue by pressing the key, Enter Object (2) and then type according to the example below:

    Name RA DEC Epoch ProperMotionRA ProperMotionDec Magnitude

    SN1995N 14:49:28.27 -10:10:15.40 2000.0 0.00 0.00 0.00
    The proper motion should be given in arcseconds/year

  • Add a catalogue of blank fields, if needed, for obtaining twilight flats fields by typing read blanks on the TCS.
  • To select an object, press the catalogue button CAT on the TCS, and then use key number 1 or 7 to move to the next or previous object, or use the Prev/Next buttons to scroll up/down an entire page. The telescope will move to the selected target when pressing the key Preset to selected (4), or if observing on the parallactic angle, pressing the key Preset to par ang (6).

Obtaining calibration frames

For StanCam it is recommended to obtain at least one set of bias frames in the afternoon and even though twilight flats should do a good job, it does not make any harm to take a set of dome flats as well for the broad band filters.
For dome flats, place the "Dome FF Lamp" under the telescope, open the mirror covers, check the ccd-probe position and choose the desired filter. The expected integration times are about 150,30,20,15,15 seconds for BVRI, SDSS z respectively, if the telescope is pointing zenith. Note that the integration times are dependent on the telescope altitude and the location of the lamp.

Start of the night

Overview of things to do at sunset

  • Power-on the telescope and open the dome following the procedure in the Cookbook

  • Once the telescope power is on, switch to StanCam. Run the script
    [obs@tessa]$ tcs.setup-tel-stancam
    in the StanCam Sequencer window. This script sets up the telescope for observing with StanCam.

  • Starting at sunset, run any sky-flat scripts that are needed.

  • When it is dark outside, switch on the two guiding monitors, and activate the guider at the TCS terminal or in a Sequencer window:
    Note that tv-on needs to be issued every time the telescope has been parked at zenith.

Telescope Startup Procedure

Return to the dome at least 30 minutes before twilight and follow the instructions below.

Weather precautions

Humidity Wind Dusty Wind Temperature
> 90% - Close telescope

After 20min < 90% the telescope can be reopened.
12 m/s - Close sideports and lower hatch 10 m/s - Close sideports and lower hatch If the humidity is > 90% and the temperature is
< 0° C close telescope and do not open until all ice has melted on the outside of the dome.
15 m/s - Observe down wind: at least 85 degrees in AZ away from wind 12 m/s - Close telescope
20 m/s - Close telescope

Telescope Control System (TCS)

  1. Turn up the brightness of the TCS screen (on right-hand side, below the screen).
  2. Look at the top-left of the TCS screen. If the item ST isincrementing, then the TCS is running, if not - then the TCS needs rebooting (rebooting the TCS should be done under guidance of a staff member). Type refresh if the screen looks strange.

Telescope power-on and Dome Opening

  1. Check the safety system in the computer room. Reset the system by turning the left key (marked as "First") and then the right key (marked as "Second"), one at a time (See TCS Manual Sect. 10.1 for procedure). If you hear a repeated clanking sound then the system has not reset, check the red lights above the keys to see if a safety stop or other item is set.
  2. Type on the TCS, power-on and confirm with y for yes. Look at the status page number 1 (type sh-p 1). On this page the status of the power units for the telescope motors can be viewed. When the TopUnitPower is on and the telescope is Idle, the telescope is ready to use. The power-on procedure takes about one minute in total.
  3. Dome can be opened about an hour before sunset if you first turn telescope to the hoist position tcs.Building-Hoist-Position or point to a blank field which is away from the sun tcs.goto Blankxx+xx. Upper hatch and lower hatch can be opened normally, but leave north sideport closed west south east. After sunset open north sideport as well
  4. At sunset, if weather conditions are OK, open the upper hatch with the mirror covers closed. Press the key, START/STOP on the TCS and then the key Open Upper Hatch (7). Confirm by typing y for yes. It takes about 3.5 minutes to open the upper hatch.
  5. In the dome (While the upper hatch opens) check that nothing is in the way of the telescope motion (altitude: 6.5° - 90°)
  6. Open the side ports (only if weather conditions are OK and the sun is under the horizon). Type on TCS, open-side-ports-fully. Look at the TCS status page number 3 (type sh-p 3). Status page 31 shows more details, but is delayed in updating. For manual opening procedure of the sideports see Sideport Operation . The side ports can be operated individually and opened before sunset by typing in TCS open-side-ports-fully south or respectively east, west, north based on the sun position.
  7. Open the lower hatch (only if weather conditions are OK). On the TCS, press the keys Start/Stop and Open Lower Hatch (8). Confirm with a y. It takes about two minutes to open the lower hatch. The TCS will not allow opening of the lower hatch before the upper hatch has completed opening. In case you can only open the upper hatch, the maximum zenith distance for unvignetted observing is 55°, and at a zenith distance of about 70° roughly half of the mirror is vignetted.
  8. The mirror covers can be opened at the same time as the lower hatch. On the TCS, press the keys Start/Stop and Open Mirror Covers (9). Confirm with a y. It takes about 50 seconds to open the mirror covers. Please note that the power for hatches and mirror covers is completely independent of the telescope power and the electronics in the control room.

Set default telescope parameters

  1. This should be done in any sequencer terminal with
    [obs@tessa]$ setup-tel-stancam
    This sets amongst other items, the default telescope focus and rotator angle, and auto-pos-full for fully automatic autoguiding when pointing to an object.


Field Rotator

In an alt-az telescope the field rotator is used to keep the orientation on the sky fixed while tracking. When the field rotator is in automatic mode, which is the default, the TCS command field-rotation value sets the rotator such that value is the angle between the sky and the instrument. The default value of the Field Rotator is different for each instrument and can be found in Table 1. The field-rotation value will be set to the default angle when executing the script setup-tel-stancam

The rotator-position is the physical position of the rotator with respect to the telescope fork, and it has a limit at +- 200 degrees. Its current value is shown on the TCS status display together with the time-to-reach-limit in minutes. Before reaching the limit, the TCS will send a warning and suggest you to turn the rotator 360 degrees at any convenient moment. This can be done manually with the TCS command ro-tu-360 after switching off autoguiding with ag-off. Note that this is possible only in the overlapping ranges [-200,-160] and [160,200]. If the limit is reached, the TCS will eventually, after repeated warnings, perform the full rotation automatically (whether or not an observation is ongoing).

The exposure commands for ALFOSC, FIES, MOSCA and StanCam check whether the rotator limit is reached within the exposure time, if this is larger than 300 seconds. For NOTCam, where typically multiple short exposures are made, this is not the case. If you want to follow the same target continuously for many hours, and you wish to avoid having to turn the rotator, for instance because you want your target on exactly the same pixels all the time (transit light curves), you might consider using a different field-rotation value, based on the time-to-reach-limit value displayed on the TCS UIF.

For the case that right after the telescope pointing the rotator will start off in the overlapping rotator range, the telescope can be told to automatically point using the rotator position that allows for maximum tracking time, with tcs.set-rotator-standard, which is the default behaviour. For details see the TCS documentation. If you have many pointings with relatively short exposures or you keep pointing towards the same region of the sky, you may save some pointing overheads by making the TCS choose the fastest rotator slew to reach either of the overlapping rotator ranges: set the rotator to fast mode using tcs.set-rotator-fast, which is a sticky command. To go back to the default mode, use the command tcs.set-rotator-standard .

Camera Probe

The Camera Probe is used for the standby Camera (StanCam) and for FIES and should be put in park position for all other instruments. Put the Camera Probe in the correct position by typing the TCS command as indicated in Table 1. The correct Camera-Probe position will be set when executing the script setup-tel-stancam

Sky Flats

If you are observing in imaging mode, obtain sky flats in the evening twilight with the filters you are going to use. If you know before hand that you might be requested to perform observations for a Target of Opportunity (ToO), it could be convenient to obtain sky flat fields in the standard filters (U, B, V, R, i) already in the evening. The type of calibration frames needed depend very much on your science goals and the instrument mode you are using. We recommend the documentation on the instrument pages. Please, check the User Guides available for: Stancam

Below is a short guide of how to obtain twilight flat fields for optical imaging.

  • Remember to set tv-off on the TCS before making sky flat fields (adequate for morning flat fields, the TV monitor is often already off in the evening).
  • Choose a proper blank field from the blanks catalogue. A useful blank field target in the eastern sky that is not too low (i.e. RA 1-4 hours more than current ST).
  • point the telescope to the blank field:e.g.
    tcs.goto-object Blank03+31 from the sequencer terminal or
    goto-object Blank03+31 from the TCS.
    • You can also read the full catalogue:
    • Load a catalogue containing empty fields by typing read blanks on the TCS. Access the catalogue by pressing the key CAT and select an empty field with the keys 1, 7, or Prev, Next. Preset the telescope by pressing the key Preset to selected (4).
  • It is recommended to be close to the focus for each filter. Type foc-pos value where value is the default focus for the instrument and can be found in Table 1. Then type foc-del value where value is the focus offset (focus delta) for the filter, see full focus offset table and remember to change the value of the focus delta when you are changing filter.
  • Choose the desired filter
  • Make an exposure by typing expose t in the sequencer window where t is the exposure time in seconds. It is recommended to make a small offset between each image in order to be able to remove stars from the frames. To make an offset, choose the move mode Telescope RA/DEC of the TCS by pressing 5 on the numerical key pad until the right move mode is selected. Then make sure that the offset size is put to a suitable value by typing o-s x y on the TCS, where the value of x and y is in arcseconds (it is recommended to use an offset size of ten times the size of the FWHM of the seeing disk in order to easily filter out the stars). Make the actual offset while the CCD is reading out by pressing down AltFunc together with any of the arrow keys (make the offsets in the same direction). One keystroke corresponds to the value of the offset size. Repeat for next filter.
  • For flat fields aim for a count level in the range 20-30 kADU per pixel, with the useful range being about 10 - 50 kADU per pixel. The limits are based on the signal-to-noise ratio and the risk of having over exposed pixels.


It is recommended to have the telescope autoguide on an optical source close to your target object. The TCS is automatically selecting a star from the HST guide star catalogue. The guide probe is then automatically placed at the correct position to auto-guide on this star.

  1. After obtaining sky flats, switch on the two Guide TV monitors above the TCS monitor. When it is dark outside, type tv-on on the TCS to power on the TV guide camera. Alternatively, use in any Sequencer window
    The TCS command tv-off switches the TV camera off.
  2. On the TCS, type auto-pos-full to choose the fully automatic guiding mode. Note that this is the default guiding mode as set in tcs.setup-tel-<inst>. In this mode, a guide star will be automatically found, centered on the screen and autoguiding will be switched on (ag-on).
    If the guiding does not start automatically but you see a guide star on the TV monitor, type auto-pos-retry.

  3. The TV filter can be adjusted to the intensity of the guide star by typing tv-filt name on the TCS, where the options for name is Open, Closed, Grey, Red, Yellow or Blue. Choose an appropriate TV filter based on the brightness of the guiding object and keep an eye on the guide monitors during your observations so you can change TV filter after weather conditions and brightness of the guide stars.
  4. The autoguider TV focus is also set by the script tcs.setup-tel-<inst>. The TV focus is depending on instrument and can be adjusted by typing tv-foc value on the TCS, where the value for default focus is found in Table 1.
    If you wish the TV-focus to follow the telescope focus type au-t-f (Automatic-TV-Focus, default setting) on the TCS, else to restrict to only manual TV-focus settings type ma-t-f (Manual-TV-Focus).
    In automatic mode, after every pointing of the telescope the TV-focus will be set to a default value that takes the telescope-focus position into account. If that value is not adequate, you can recalibrate the TV-focus on the spot: after adjusting the tv-focus type calibrate-tv-focus in the TCS interface.
    Note, do not change the TV-focus while integrating or while placing an object on a slit. For example, the position of a star on ALFOSC CCD can move up to 1 second of arc by adjusting the TV focus by 25 units.
  5. If you want to choose a new guide star, type get-guide-star 2 (or 3,4,5, etc.) to get a new guide star from the guide server at the current pointing, followed by auto-pos-retry.
  6. On the TCS, the signal strength from the autoguider is shown as a number. A guiding value between 1 and 23 is useful. Put in a filter if the signal is above 24, otherwise the TV filter will be set to grey automatically. If the signal is close to 1 the autoguiding is not reliable (e.g. clouds and/or bad seeing). Set tv-filt open and check for clouds.
  7. Make sure that the smaller box, the sky box is placed outside the star box. If needed, move the sky box by selecting the function Sky Box with Change move mode (5) and move the box with the keystroke combination, Alt Function + arrow keys.

    Always turn-off autoguiding (ag-off) before moving the telescope.

Hints for manual guiding and tweaking of telescope pointing

If guiding mode is set to auto-pos-off, the guiding has to be activated manually. Furthermore, in case that the pointing is not optimal, some manual tweaking may be required.

For manual choosing of a guide star, start with preseting to target. Find a guide star on the screen and move the star box to the star by pressing the key change move mode (5) on the TCS several times until the option Star Box is shown. Move the box by using the keystroke combination Alt Funtion + arrow keys. Alternatively, choose the move mode Guide Probe to move the star into the box, or use the command move-g. To set the step size of the Guide Probe, type probe-step-size x y on the TCS, where x and y are in arcseconds.

In case the telescope pointing is not optimal, in particular if the guide star ends up outside the screen, a pointing correction can be made with the move mode called Telescope: press the key change move mode (5) on the TCS several times until the option Telescope is shown, and move the star by using the keystroke combination Alt Funtion + arrow keys. The step size of the Telescope is set with the command offset-size on the TCS UIF.

Alternatively, if no guide star can be found on the screen, use get-guide-star 2 (or 3,4,5, etc.) to get a new guide star from the guide server at the current pointing.

If still no guide-star is seen on the guide TV, the Aladin@NOT tool allows to identify suitable guide stars:
in "Guide probe" view, use the pointer to read off (GP_X, GP_Y) coordinates of a suitable guide star inside the red-lined GP area, and then use the TCS UIF to move the guide-probe to those coordinates with commands x GP_X and y GP_Y.

When the star is placed in the starbox, type ag-on on the TCS to switch on autoguiding. To switch off the autoguiding, type ag-off.

Guiding on moving targets

If you are observing moving targets, view the page Tracking of Moving Targets, in the Appendix.

Focusing the Telescope

Focusing the Telescope with STANCAM

The telescope focus depends on temperature and zenith distance. These relations have been measured to a high accuracy and the corresponding corrections are applied in real time by the TCS (note that you will not see these corrections in the focus value displayed on the TCS since this value is kept constant to avoid confusing the observer).

Focusing StanCam - step by step

  1. run script stancam.focus
    This script will find a proper focus field, takes and analyses the data and set the new StanCam telescope focus value.

    In case you want to change the "Telescope focus step size" use the switch "-s" e.g.

    stancam.focus -s 75
    Scroll this page to find the documentation of the focus-command

    Instructions how to take and analyse the data manually

Start Observing

When the telescope is focused it is time to start the observations. Visit the individual pages for instrument specific information: Stancam

Overview: observing an object at night

  • Point the telescope using the TCS terminal, or use the tcs.append-object and tcs.goto-object commands in a Sequencer window.
  • Make sure the telescope is autoguiding (auto-pos-full or ag-on)
  • Choose the desired filter e.g.
    [obs@tessa]$ ccd-filter 4
    or ccd-filter 4 when using the TCS terminal
  • Adjust the telescope focus, if needed
  • Make sure the CCD setup is correct (windowing, binning)
  • Start integrating e.g.
    [obs@tessa]$expose 120
    or use a script, see the StanCam sequencer commands.
  • Use DS9 and Analysis scripts for examine the image.
    Note the "teloffset" x and y-coordinates are as in the "postprocessing" ds9-display.
  • Switch-off autoguiding with
    or from the TCS terminal ag-off before pointing the telescope to the next object

End of the night

Overview of things to do at the end of the night

Closing Down Procedure

Closing the telescope

  1. When observations finish and the sky is brightening turn the guide TV off by typing tv-off on the TCS, i.e. before potentially taking morning skyflats.
  2. Put the telescope to zenith by typing zenith or pressing the key Start/Stop and then Zenith (0). This will park the guide probe and it also sets rot-man. Wait for Rotator -90°.
  3. Park the building by pressing the key Start/Stop and then the key 4, Park Building. This process can take up to 8 minutes. Building will stop at Az ≈ 119°, Alt ≈ 90°.
  4. Close the mirror covers with the TCS command c-m-c or by pressing key 3, Close Mirror Covers (if you are in the Start/Stop menu). This takes 42 seconds.
  5. Close the lower hatch by typing c-l-h or pressing key 2, Close Lower Hatch. This takes about 3 minutes.
  6. Close the upper hatch by typing c-u-h or pressing key 1, Close Upper Hatch. This takes about 5 minutes. If timeout occurs or hatch does not move, see TCS Manual p. 43.
    NB: When the upper hatch has closed the dome cooling will start and the staircase cooling will stop.
  7. Close the side ports by typing on the TCS UIF close-side-ports. Check that all sideports did close by checking status in TCS page 3, type sh-p 3. If a sideport does not close, go to the dome and flip the black knob from remote to local and press the green button to move the sideport in question. For more details, see Sideport Operation.
  8. Power down the telescope. After all of the above have been completed, type power-off on the TCS, then type sh-p 1 to display the telescope power units. Wait until all the telescope power displays show "off".
  9. Run the calibration script (if you observe with ALFOSC or NOTCam), i.e. alfosc-calibs ALxxxx or notcam-calibs NCxxxx, where xxxx refer to the file prefix for the night.
  10. Turn down the TCS screen brightness. Use the knob on the right-hand side of the TCS monitor, near the power switch. Never turn the TCS monitor off.
  11. Turn off monitors. Turn off the two autoguider monitors and dome TV camera monitor.
  12. Turn on the control room webcam and the dome webcams. Make sure that the webcams in the control room as well as in the dome are turned on before you leave.
  13. Have a look in the dome at hatches and telescope, to check for any faults that might have occurred.
  14. Complete the WWW report forms. Fill in and submit Internet NOT End-of-Night Report. Be sure to include any faults that occurred and submit a fault report, so we can attend to problems promptly. If it is the last night of the observing run, also fill in and submit Internet NOT End-of-Run Report.
  15. Lockup the dome. Lock the outer dome door when you leave the building.
  16. Clean up the kitchen/lounge area in the service building and switch off all lights when you leave.
  17. Lockup the outer door in the service building before leaving for the Residencia.

Stopping the StanCam observing system

  1. In a terminal window type
    shutdownobssys stancam
  2. Wait for all the control programs to close.
  3. Occationally, it can happen that the Talker (the log) or the SEQ Xterm does not close. Then please close them manually.
  4. To exit the STANCAM Obs Log, press escape in the frame of the STANCAM Obs Log window.

Data saving and retrieval

Instructions on how to retrieve data from ALFOSC, NOTCam, StanCam, MOSCA and FIES are found in Data Download instructions.

Only principal investigators have direct access to their data on the data server. The principal investigators can grant access to their data by generating and distributing a shared link. Details on how to do so can be found in the instructions.

General information on NOT FITS-headers can be found here.

Accessing raw and reduced data at night

The computer called florence is setup for you to make a quicklook analysis of the incoming data, e.g. by starting up DS9 and IRAF:

   > cd newiraf 
   > ds9
   > xgterm -sb -fn 9x15 -sl 400 -cr red -title IRAF -e ecl & 

For the different instruments we have on-line reduction programs running, that deposit the reduced products on a disk accessible on florence.

The raw and reduced data files can be found on florence under directories

Copying data products from florence over the wifi in the NOT control room to your own mobile computer is no longer feasible. Use the Data Download tool.

Archival requests

To obtain NOT data from our archive, first compile a list of file names of the calibration and science data to be retrieved, using our FITS archive. Note that this archive does not show the data obtained in the latest twelve months, due to the propriatary period.
Then please contact staff and send the list of file names to be retrieved, such that we can locate the data in our archive and make them available through FTP.

Compensation for override observations

If your program was interrupted by a Target-of-Opportunity or another override observing program, you are entitled to payback time. Such compensation for time lost during your allocated observing run (whether in visitor or service mode), is claimed back through the submission of Observing Blocks (OBs) using our OB Generator. The observations will be executed accordingly in service mode by staff during Nordice Service nights, and you will be informed by email when observations are made and where to retrieve the data.

Using the OB generator to claim payback time

Access the Observing Block Generator and login to your account, or if you are a new user, please register. When you are logged in, add your proposal for which you claim compensation time. There are help buttons at every level of the OB generator, and you can also get support and give feedback through If you have questions about how to define OBs and/or Observing Sequences, please contact

For your OBs to be carried out as compensation for time lost to overrides, please make sure to select OB Group type "Payback".


If you have ...

  • ... cannot reset the safety system:
  • ... no light on the CCD -- check:
    • Dome open, mirror cover open
    • Lower hatch not obstructing at low altitude
    • Guide probe out of light path
    • Camera probe in correct position
    • FASU shutter open (if using ALFOSC)
    • Correct filter in instrument
    • Correct telescope focus
    • If it is cloudy
    • Check all the above again. If there still is a problem, then phone duty staff.
    • If MOSCA or StanCam image has a count level of 0, this can actually mean saturation and you should reduce the amount of light falling on the detector.
    • StanCam shutter controller has power (if using StanCam)
  • ... wrong field on CCD -- check:
    • Coordinates of field
    • Epoch of coordinates
    • No typos in entering coordinates in TCS
    • Field rotation is correct
  • ... no guide star on guide probe screen -- check:
    • Dome open, mirror cover open
    • Guide probe in correct position
    • Field and rotator angle
    • TV switched on
    • TV filter open
    • TV focus correct
    • Try typing in the X and Y values of another Guide Star fromthe The 10 brightest currently available Guide Stars
    • If it is cloudy
  • ... lost tracking/guiding:
    • How close to the zenith are you? (Good guiding and tracking is guaranteed only 5 degrees or more from zenith).
  • ... changing tv filter does not work:
    • at TCS type in the command 'Initialize-TV-Filter'.
  • ... ctrl x', 'ctrl g', 'ctrl t' and 'ctrl v' commands on the TCS give incorrect functionality, e.g. telescope offset rather than star box movement.
    • wrong function key menu on the TCS keyboard press keypad key 5.
  • ... "building crash":
  • ... other TCS problems
    • Press the keypad key labelled Log and then keypad 2 to see the latest entries in the TCS log.
  • ... acquisition: slitoff/fiboff unresponsive
    • Using the mouse to set the contrast while image is loading?
      Using the mouse to set the contrast while this process takes place can cause DS9 to crash. Best procedure is to wait tuning the contrast level until the image has been fully loaded into DS9, and zoom / contrast levels set.
      A DS9 crash while in 'imexam' while leave the postprocessing system in a non-workable state.
      Rather than shutting down the whole observing system to recover, it is in most cases sufficient to run the sequencer command 'killimexam'.
      See also next item.
  • ... ds9 shutting down while doing acquisition
    • Using the mouse to set the contrast while image is loading?
      Using the mouse to set the contrast while this process takes place can cause DS9 to crash. Best procedure is to wait tuning the contrast level until the image has been fully loaded into DS9, and zoom / contrast levels set.
      A DS9 crash while in 'imexam' while leave the postprocessing system in a non-workable state. Rather than shutting down the whole observing system to recover, it is in most cases sufficient to run the sequencer command 'killimexam'.
  • ... "sequencer/obssys" does not respond or behaves badly:
    • Standard procedure in such circumstances is to restart the observing system using 'shutdownobssys' (from a terminal window) followed by 'startobssys'.
  • ... lisa frozen, not responding, e.g. can not log out using the foot icon
    • if you have a working terminal, try "$ killall panel", wait until the panel restarts and then logout as usual
    • if there's no terminal available, you can use florence to ssh as obs into the observing computer you've been using, and type the killall command.
    • if you have no terminal available, etc. press the "Ctrl" and "Alt" keys and then press "Backspace". That will kill the X server and force a logout

If you encounter a fault or a problem with the instrument, the computers or the telescopeduring the night, then fill in a Fault Report.


Tables for Instrument Settings

instrument field-rot i-p-a camera probe foc-pos tv-foc orientation c-w-h
ALFOSC +90 0 (horizontal slits)±90 (vertical slits) c-p-p 26630 510 North ↑ East ← Horizontal slits: E-W (P.A. = ±90) 0.75
FIES 0 N/A c-p-s 26880 510 North ↓ East ← N/A
NOTCam -90 -90 c-p-p 26750 500 North → East ↑ 0.95
MOSCA -90 N/A c-p-p 27160 450 North ↑ East ← 0.55
StanCam 0 N/A c-p-c 26330 500 North ↑ East ← N/A
SOFIN 0 -90 c-p-p 26950 510 N/A 0.9
TurPol 0 N/A c-p-p 29450 650 North ↑ East → 0.12

Table 1a shows the values of the: field rotation(field-r), instrument-parallactic-angle (i-p-a), ccd probe, focusposition (foc-pos), TV focus (tv-foc), field orientation andcounter weight height (c-w-h) for the different instruments. On the TCS, type thecommand followed by the value, for instance field-r -90. The default focus value stated for NOTCam is for the K band in imaging mode using the WF camera (internal camera focus of 5650).

From To foc-delta
ALFOSC no filter StanCam R-filter (#10) -260
MOSCA R-filter (#106) StanCam R-filter (#10) -155
NOTCam Ks-filter (WF) StanCam R-filter (#10) -380

Table 1b shows the default focus offsets between the instruments.

Commonly Used Instrument Commands

Command Comments
CNTR-C kill ongoing command or script
abort kill ongoing exposure

object text Sets the value of the FITS keyword OBJECT to text
autosave_on Turns on autosave. For off, type autosave_off
rempath link Sets the remote saving path to specified link
remsave_on Turns on remote saving. For off, type remsave_off
bin n Sets the binning factor in both X and Y directions to n
xbeg n Sets the X beginning to n (use ybeg for y).
xsize n Sets the X size to n (use ysize for y).
expose t Makes an exposure of t seconds. To abort the exposure press Ctrl-C and type abort in the sequencer window.
mexpose t n Makes n exposures of t seconds
dark t Makes an dark exposure of t seconds
mdark t n Makes n dark exposure of t seconds
teloffset n m Offsets the telescope in the CCD X,Y direction by the amount n in the X direction and m in the Y direction. n and m are given in arcseconds.
resetxy Resets the CCD to unbinned full-size readout
For more commands, view the Sequencer Reference Manual.

Commonly Used TCS Commands

Command Comments
ag-on Turns autoguiding on
ag-off Turns autoguiding off
auto-positioning-full Turns the guide star auto positioning to full-automatic
auto-positioning-retry Try again to bring the guide star in the guide box
Moves the camera probe to ccd position (for StanCam)
camera-probe-park Moves the camera probe to park position (for ALFOSC)
Moves the camera probe to split position (for FIES)
field-rotation fieldangle Sets the field rotation to fieldangle
focus-position n Moves the telescope to focus position n
focus-delta n Applies a focus offset to the current telescope focus
get-guide-star 2 Find another guide star
instrument-parallactic-angle n Defines the parallactic angle for following presets
read-catalogue Reads the catalogue
tv-on Turns on the guide TV
tv-filter name Selects the guide TV filter where name can be either closed, grey, open, red, yellow or blue
tv-foc pos Changes the guide TV focus to position pos

append-object string appends an object to the TCS catalog
goto-object Object moves telescope to "Object"
find-object selects an object in the TCS catalog
preset-with-parallactic-angle-to-selected moves telescope to the selected object, with parallactic angle
For more commands, view the TCS SEQUENCER Command Reference.

Tracking of Moving Targets

At the NOT there are two main modes of tracking a moving object (planet, comet, asteroid, satellite): 1) differential tracking with auto-guiding and 2) differential tracking without auto-guiding. Which of these to use, depends in practice on the target speed and how long the observations take. We have been working with speeds as high as 700"/hour with auto-guiding.

Since September 2019 the OB generator allows for non-sidereal tracking.

The differential rates are given in the FITS headers in the keywords DTRCK_RA and DTRCK_DE.

Differential tracking with auto-guiding

In this mode, the telescope tracking is set to the differential rates, and in addition, the auto-guider is used with the star-box set in motion with the same rates. This works for as long as the box stays within the auto-guider TV-screen (approximately 70" field). When the limit is reached, auto-guiding is no longer working. It is possible to reposition the star-box and guide probe without affecting the telescope tracking, but there is a limit to how many times this can be done before reaching the limit of the available guide probe area. This depends on the RA/DEC rates, the field-rotator angle, and the initial location of the guide star inside the guide probe area. If this happens, you have to repoint to the target again.

If your target moves less than 70" over the execution time of your observations, you can relax. If it moves more, you need to keep an eye on the star-box and manually re-position it as described under step 3 below. Both the telescope tracking rate and the box-motion rate are given in RA/DEC coordinates, i.e. dDEC/dt and dRA/dt (in arcsec per hour), and the cos(DEC) correction is taken care of internally by the TCS. (In other words, if your RA-rate is given as dRA*cos(DEC), you have to divide by cos(DEC) before entering its value.)

  1. From ephemeris get the target's position and coordinate motion for the time of observation. Coordinate motion is the RA and DEC rates (dRA/dt and dDEC/dt) in arcseconds per hour. We recommend to use the sequencer script:

    tcs.asteph -n TARGET

    where TARGET must be the official JPL Horizons name and surrounded by escape double quotes if it contains a space. The script looks up JPL Horizon and finds position and rates for this moment at the location of the NOT (Z23), converts from dRA/dt*cos(DEC) to dRA/dt, as required by our TCS, and lists the sequencer commands you need to point to target and start differential tracking AND differential auto-guiding.

    It is highly recommended to test tcs.asteph in the afternoon. See example below (in green). Type tcs.asteph to get a listing of input parameters, note that all optional parameters must be given before the "-n TARGET".
  2.         Usage: tcs.asteph [ -t asteroid|comet|planet ] [ -m ima|para|along-slit|optimal-ll|optimal-lr ] [ -r full|half ]  -n TARGET   
           -t default type is "asteroid"
              option "planet" selects for instance the Jovian satellite Europa instead of the asteroid Europa
              option "comet" 
           -m default mode is "ima" using the default field rotation for imaging 
              option "para" for spectroscopy orients the slit along the parallactic angle
              option "along-slit" orients the slit along the tracking direction of the target
              option "optimal-ll" orients the field to  maximize the number of guide-probe repositions
              option "optimal-lr" 180 degrees rotatated to above, both recommended for fast targets or long observations
           -r default tracking rate is "full"         
              option "half" gives the half-rates of the differential tracking (sometimes requested)
           -n \"target name\" is mandatory (if it contains a space, use escape double quotes)
    The two modes "optimal-ll" and "optimal-lr" are intended for very fast objects or very long observations.


    [obs@selena ~][11:28][ALFOSC]$ tcs.asteph -n \"C/2019 Q4\"
    * For instance: tcs.asteph -n \"2019 K2\"
    cd /home/postprocess/telescope/v3; source /home/postprocess/.virtualenvs/27/bin/activate; bash -n "C/2019 Q4"
    Running tcs.asteph...
    Your input target is                        -  C/2019 Q4
    Your observatory is Nordic Optical Telescope, La Palma.
    Retrieving data from JPL Horizons...
    Data retrieved successfully from JPL Horizons.
    The object being searched for is  Borisov_C-2019_Q4
    Prefix for file names will be  2022-May-27.Borisov_C-2019_Q4
    Today is  2022-05-27
    Your computer says time is  11:28  UTC.
    These tasks should be given to the TCS:
    tcs.append-object Borisov_C-2019_Q4 17 41 17.92 -58 15 21.8 2000.0 0.0 0.0 25.612 Borisov_C-2019_Q4
    tcs.reposition-guide-probe -12.5412 -0.46244
  3. Cut and paste the three first sequencer commands listed by tcs.asteph (or point to your target in the normal way), wait until guiding, and then cut and paste the fourth command or run it as:

    tcs.reposition-guide-probe RA-rate DEC-rate

    This is a script which will 1) stop auto-guiding and box motion (if it was set in motion), 2) move the star box to an optimal position on the TV screen, 3) set the telescope tracking rates to RA-rate and DEC-rate, 4) start the box motion to the same rates, 5) move the guide probe to put the star in the box, and 6) start differential auto-guiding.
  4. If this is a relatively fast target, i.e. moving more than 70" during the time your observations take, you will have to keep an eye on the star box. When it reaches the other edge of the TV screen, it will stop guiding. The TCS will send warning beeps when there is 120, 90 and 60 seconds left. Make sure you take action before guiding stops by re-running the command:

    tcs.reposition-guide-probe RA-rate DEC-rate

    in another sequencer window. You can do this while exposing, although it is optimal during readout, in between exposures. This repositions the box and the guide probe and continues differential autoguiding without affecting the telescope tracking.
  5. There is a limit to how many times you can reposition the guide probe due to the limited guide probe area. If this happens, you have to start again from point 1.

The telescope resets to the sidereal tracking rates at every new telescope preset/pointing so nothing is needed at the end of the observation.

However, for your information, you may stop the differential guiding by (or in short on the TCS UIF b-m-sto). This does not reset the telescope tracking rates, and if you wish to stop the differential tracking, going back to normal tracking rates, then on the TCS UIF type set-rate 0 0.

Tracking without auto-guiding. Rapidly Moving Targets

For more rapidly moving targets, use the set-rate command on the TCS to continuously move the telescope from a pre-calculated change in position. RA-rate and DEC-rate as above. In this mode auto-guiding is not used.

We are also upgrading the possibilities for very fast tracking (without autoguiding), and the software speed limit has been increased from 17"/s to more than 5000"/s. Observations were made of fast satellites where the RA/DEC rates were updated every second.

  1. Preset to your object.
  2. Set the rate of change by set-rate RA-rate DEC-rate (rate in arcsec per hour). The maximum differential rate is 20000000 arcsec/hour (≈ 5500 arcsec/s).
  3. Make the exposure.
  4. Reset by typing set-rate 0 0 on the TCS.

For Experts Only

If the target has an unknown or rapidly changing motion, you might want to adjust the rate of change in RA and DEC while tracking. Use the set-rate command on the TCS and use command recall with the up/down keys and edit the set-rate.

  1. Preset to object.
  2. Guess the starting set-rate RA-rate DEC-rate values.
  3. Do as described above with command recall.
  4. Do set-rate 0 0 or just preset to another object.

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