SofI Overview

SOFI is the infrared spectrograph and imaging camera on the NTT. The optical layout can be viewed in Figure 1 and Figure 2.

The instrument is equiped with a Hawaii HgCdTe 1024x1024 array with sqared 18.5 micron pixels, sensitive to light within 0.9-2.5 micron range. The peak quantum efficiency is 65 %, the gain is about 5.4 e/ADU, and the read-out-noise is about 2.1 ADU. The array is linear to less than 1.5 % for signal below 10000 ADU.

The instrument offers the following observing modes:

  • imaging with plate scales of 0.144, 0.273 and 0.288 arc-seconds/pixel using broad and narrow band filters in the wavelength range 0.9 to 2.5 microns. Click here to check the image quality in the different configurations.
    Only the large field mode with the plate scale of 0.288 arc-seconds/pixel is offered as of Period 80.
  • low resolution (R=600) and medium resolution (R=1200-1500), 0.93-2.54 micron spectroscopy with fixed width slits of 0.6, 1 and 2 arc seconds.
  • 0.9-2.5 micron imaging polarimetry (postscript).
  • High time-resolution imaging in burst and fast photometry mode with integration times of the order of a few tens of milliseconds via hardware windowing of the detector array.

CCD Characteristics

Array FormatHawaii HgCdTe 1024x1024
Pixel Size18.5 µ
Q.E. 65%
Gain ~ 5.4 e/ADU
RON  ~ 2.1 ADU 
Bad Pixels About 1000
Non-Linearity  < 1.5% over 0 to 10000 ADU 
Dark Current  < 0.1 e/s 

Brief Overview

See also a brief overview of SOFI's history.

Publication Metrics

SofI Publication Metrics (Last modiefied 2012-05-13)

Last modiefied: 2012-05-13, V.D. Ivanov

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