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Optical Camera with ELectronmultiplying OutpuT

OCELOT is an Andor iXon+888 EMCDD camera mainly mounted on the RCC telescope. For the operating instructions, see the article Usage of OCELOT on the RCC. It can also be mounted on the 50 cm Cassegrain telescope. Furthermore, it is vital to consult the article Ocelot.



To use the EMCCD we first need to stop the spectrograph: acectrl --stop. This ensures that the mirror within the telescope tube directs the light in the EMCCD instead of the spectrograph.



  • Sensor: e2V CCD201-20
  • Sensor size: 1024*1024
  • Pixel size: 13 μm * 13 μm
  • Image area: 13.3 mm * 13.3 mm
  • Active area pixel well depth: 80 000 electron (typ.)
  • Gain regeister pixel well depth: 730 000 electron (typ.)
  • Max readout rate: 10 MHz
  • Frame rates (full frame): 8.9 frames per sec
  • Read noise (10 MHz): 1 to 47 electron
  • Peak quantum efficiency (575 nm, typ.): 92.5%
  • Cooling: thermoelectric + liquid, -90°C

Optical parameters

On the 1 m RCC telescope:

  • Field of view: 3.36 arcmin x 3.36 arcmin
  • Resolution: 0.2 arcsec per pixel

On the 50 cm Cassegrain telescope:

  • Field of view: 6.88 arcmin x 6.88 arcmin
  • Resolution: 0.4 arcsec per pixel

CCD characteristics

Readout Preamp gain EM gain Effective gain (ADU/electrons)
16bit/1Mhz 5.1 10 6.58 +/- 0.06
16bit/1Mhz 5.1 20 13.40 +/- 0.10
16bit/1Mhz 5.1 40 27.67 +/- 0.39

Note: the usual definition for a gain value is in the units of electrons/ADU (e.g. as it is used in the widely accepted GAIN keyword in FITS files), hence it is the reciprocal of the above values. For instance, the argument --gain of the fiphot tasks of FITSH also expects gain values in electrons/ADU units. However, in the case of a detector electronmultiplying output, the units of ADU/electrons are more closery related to the EMCCD hardware characteristics: the gain in ADU/electrons is quite proportional to the set value of EM gain.


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