Observing with VATT

Getting started

  1. Either
    1. use the PEPSI 4K monitor in the LBT control room,
    2. connect to it from VATT
      • using ‘vattarchive’ server
      • login as ‘vattobserver’, passwd is at control room
      • type in terminal vncviewer -via ajarvinen@ssh.lbto.org -shared
      • passwd is the standard pepsi passwd
    3. observe remotely
      • take VNC connection by typing in terminal vncviewer -via ajarvinen@ssh.lbto.org -shared
      • environment status can be seen at
      • passwd is given on need to know basis
  2. The program should be kept running all the time. If it is not running, click Activities in the left upper corner. You should get a menu having PEPSI logo. Click on that logo to open the program. Or use a terminal to open it (if not, open a new terminal)
      • if on pepsib, then type ‘alpha
      • cd data/pepsi/current
      • type ‘pepsi’


Guiding and observing

  1. Now you should have ‘PEPSI Control Interface’ open.
    • Click on VATT check button to connect and open ‘VATT control interface
    • Check that VATT radio button is selected
  2. Two more windows should appear
  3. Click ‘Blocks’ button on ‘PEPSI Control Interface
  4. When you
    1. already have an observing block, a window opens
        1. select the target you want to observe and send it to VATT
        2. check that ‘VATT control interface’ has the same target as you chose
        3. check that ‘PEPSI Control Interface’ changed according to selected target
        4. if you need to change pre-defined exposure times, click ‘Edit fields
        5. a new window pops up and you can make the changes
          • note that values in ‘PEPSI Control Interface’ do not change unless you send the target information again (see A.)
          • you can also change values in ‘PEPSI Control Interface’ directly, but then the visibility plot does not change and block will not remember the changes made in future
    2. don’t have any targets or you want to change targets
      1. click ‘add another object’ in ‘Observing programmes’ window
      2. a new window having targets pops up
      3. choose the target and send it to the observing block
      4. continue as in 4-a.
  5. after the telescope operator gives the permission, click ‘PRESET
    • Offset buttons offsets the telescope in small steps so that the image of the direct-reflected image of the target moves on the guider CCD according to the directions of the buttons.
    • Offset step size specifies the offsets in arcsec. The default value is 5 arcsec.
    • Alternatively, one can click the target with the right button of the mouse
  6. Click ‘Guider’ to open guiding window to keep the target on the pinhole, check that ‘Pause’ is unchecked
    • At this point you may re-focus with the help of the telescope operator and possible change ‘exposure time‘ or ‘gain‘ in the ‘Guiding Camera‘ window.  During summer 2018 the focus is around -1760.
    • Normally, the gain value should be 0.4. If the star keeps jumping out of the guiding box, try to change the gain value. At southern sky gain 0.8 is sometimes needed.
    • Adjust exposure time, number of exposures, and binning according to brightness of the target. Exposure time is given in microseconds, max 0.5s. Max binning is 4.
  7. You may also want to check the hot spot, that is how well the target is centered to the fiber. If you see target spilling over asymmetrically, correct hot spot coordinates.
  8. When you are happy with the plots in ‘VATT Guider‘ window, start guiding by ‘Start
    • In the morning, make sure that you ‘Pause‘ guiding
  9. Start observations by clicking ‘Start’ in ‘PEPSI Control Interface


Viewing obtained spectra

It is good to take a look at the spectra in order to see if you should change exposure times etc.

  1. Select the spectrum you want to look at from ‘FITS Image Browser‘ with Enter
  2. The active window has a cyan frame. Select the area you want to look at closer by drawing a red box with, for example, a mouse
  3. To see a spectrum from selected area
    1. Press ‘Enter‘, or
    2. Click ‘Sigma‘ icon on top of the viewer
  4. Now you have a spectrum plot where you can see the UDUs
      • Select again an area with mouse from highest values to lowest
  5. Click ‘Sun’ icon on top of the spectrum viewer
  6. You get a pop-up window there the S/N estimate is given, save that information into fits list by clicking ‘Save


Calibration frames

After the observing night is over, it is time to take the calibration

In the ‘PEPSI Control Interface’ window:

  1. Click CHAIN button to get a pop-up window
  2. Check that for wanted fiber(s) ThAr, FPE, and Traces are chosen
  3. Click START button on Control Interface window
  4. When calibration frames are ready, click CHAIN again to stop



  • When VATT computers have to be rebooted, the connection to them is lost and PEPSI software has to be closed and restarted.
    • Close it by clicking x in ‘PEPSI Control Interface
    • Start opening as described in the beginning of the instructions.
  • Sometimes the software program freezes or even crashes. If that
    happens, find the following terminal

and type Ctrl+c