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Home > Astronomy > Telescope Operator Notes > Working with PAUCAM


The PAU (Physics of the Accelerating Universe) project succesfully saw first light at the prime focus of the WHT on June 3rd 2015. PAUCam is an advanced imager comprising a mosaic of 18 state-of-the-art, fully-depleted, red-sensitive Hamamatsu CCDs, and a field of view with a diameter of about one degree (or about 11 times the sky area covered by the WHT's current prime-focus imager), of which 40 arcminutes are unvignetted. PAUCam was designed and built by a consortium of Spanish institutions (IFAE, ICE-CSIC/IEEC and PIC from Barcelona; CIEMAT and IFT-UAM/CSIC from Madrid).

PAUCam was built to carry out the PAU Survey, designed to study the existence and properties of dark energy using galaxy Redshift Space Distortions and Weak Lensing Magnification as cosmological probes. For this purpose, PAUCam will image up to 2 square degrees per night in 40 narrow-band and 5 broad-band filters to iAB~23, providing low-resolution (R~50) photometric spectra for around 30,000 galaxies, 5000 stars and 1000 quasars per night.


  • Zeroset AZ, ALT and ROT
  • USER> FOCUS 82.30 (Apr 2016)
Check that the telescope is at zenith and the petals closed and move the Nasmyth flat to the stow position by pressing the CASS button. On the TCS it will show that the optical configuration is "Prime (Nasmyth flat stowed)".

Filling the cryostat:

The cryostat will be filled by the PAUCAM team (only the first night PAUCAM is mounted). It is at prime focus so it is necesary to park the telescope at 10 degrees elevation (or use AP2).

From the TCS:

  • USER>DOME 298
This is important to prevent water dripping from the edges of the shutter onto the camera electronics in wet conditions.
  • USER>AZ 298
  • USER>EL 10

Rotator centre and Calibrate procedure:

As of Apr 2016, this has never been done (not needed since the pointing is good and it has a large FOV).


PAUCAM autoguiding was comissioned in April 2016 although with 100s exposures they find the tracking adequate so it won't be used for the PAU Survey.

The Autoguider to TCS selection switch should be in position PAUCAM (position no. 9). When autoguiding is used the PAUCAM system will send autoguiding packets to the TCS. This should be visible on the encoders page. There is no need to find a guide star as it is self-guided. There is no need to start the guiding either unless they want to do some corrections in their scripts.

To start guiding:

  • USER> AUTO ON 50 50


The OSA should remind PAUCAM observers that they should check the instrument (at AP2) and make sure Cryotiger-lines are sufficiently dry before going on sky. In the morning after observing, keep the camera at zenith (this way the CASS instrument may be fillled) with the prime rotator at Rot Mount 0.

Orientation: To get North pointing up on the detectors (the observer will do this, Apr 2016):


Movement of target using XY HANDSET keys: It will move as shown in the keyboard, but check next time it's mounted since they still have to define the global X and Y coordinates for their detector (each detector of the array has different X and Y orientations) and their display is arbitrary rotating 180 degrees. However, this will be hardly used because the PAUCAM system will normally go to different pointings between exposures (Apr 2016, ins_ad_xy2mount(16)=0.26843163 has been included with GSEXAM but Frank still has to set it to the instrument PAUCAM and update the documentation)

Dome Flats: The observers need the telescope in dome position in the afternoon. Their system will control the dome flat lamps and will take the exposures. They might ask us to open and close the petals (or do it themselves pushing the console buttons. Now included in their system as well, May 2017).

Acquisition: The observers will usually do the GOCAT (actually GOTO), often taking short exposures with a small offset inbetween.

It is important to be sure that the rotator doesn`t reach the limit switch because the MOUNT PA range is only 357 degrees in total (limits: -163.37,193.63). Hitting the limit you can't simply unwrap, you have to wait a certain time until you get past the 3 'forbidden' degrees, which may take a while, depending where the object is on the sky, therefore watch carefully what the limits are each time they move to a new field.

To check if a rotator limit will be hit, see the AF2 rotator limits section
Data Handling

The data are handled by the PAUCAM team and do not appear in ING logs.

See also

PAUCAM instructions (last updated: 20160328).

In case any more TCS adjustments are needed (GSEXAM), please follow the links below:

PAUCAM guiding commissioning instructions for TCS users-OSAs (BSCW link, password protected).

PAUCAM commissioning instructions for TCS users-OSAs (BSCW link, password protected).

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Contact:  (Observing Support Assistant)
Last modified: 13 November 2017