SAAO - South African Astronomical Observatory

SHOC: Sutherland High-speed Optical Camera

Introduction

Two approximately identical instruments named SHOC (Sutherland High-speed Optical Camera) have recently been commissioned for use on the SAAO 1.9-m, 1.0-m, and 0.75-m telescopes.  SHOC 1 and 2 are high-speed, visible-wavelength systems, mounted at Cassegrain focus and using the existing filter wheels employed by the SAAO CCDs.   The SHOC cameras allowed the UCT CCD camera's world to end in 2012.

The SHOC design is based on POETS (Portable Occultation, Eclipse, and Transit Systems; developed by a collaboration between groups at the Massachusetts Institute of Technology (MIT) and Williams College) and the IRTF MORIS (MIT Optical Rapid Imaging System).

Technical Specification

The SHOC instruments employ Andor iXon 888 EM CCD cameras, which have an electron multiplying (EM) capability.  They are 2048x1024 13 μm pixel detectors, operated in frame-transfer mode (imaging area 1024x1024 pixels).  The following characteristics apply:

Telescope

Field of View (arcmin)

Platescale ("/pix)

1.9-m

1.3 x 1.3

0.08

1.9-m + focal reducer

2.8 x 2.8

0.16

1.0-m

2.9 x 2.9

0.17

0.75-m

3.7 x 3.7

0.22

Operating at the lowest readout speed (lowest read noise) with appropriate binning for Sutherland's median seeing, a minimum cycle time of ~0.5 seconds is typical.  With further binning, windowing and higher readout speed, the cycle time can be decreased to 0.05 seconds.

Current status & availability

Due to high demand, we have released these instruments in the commissioning phase to observers wanting to take advantage of the high-speed facility, while accepting that certain aspects are still in progress. 

Users should be aware that dedicated instrument control software is still under development.  SHOC is currently operated using the proprietary software supplied with the cameras, which has not been designed specifically for astronomy.  In particular, users should note the following:

  • Acquisition software and filter wheel control are not integrated at this stage, i.e. the instrument is ideal for high-speed photometry in one filter at a time; repeated cycling through a series of filters is not recommended as each filter change would have to be performed and recorded manually.
  • Although SHOC achieves highly accurate timing by GPS-triggering of exposures, start times are not yet recorded in the FITS headers and must be recorded manually for later addition to the headers.
  • GPS triggering is not currently available on SHOC 2, although the computer and GPS times can still be synchronised.
  • Telescope (e.g. RA, dec) and filter information are not recorded in the FITS headers.
  • Use of EM mode is strictly prohibited due to the risk of permanent damage to the CCD.

Future software will incorporate safeguards to protect the detector in EM mode.  In the meantime, observing in EM mode must not be attempted.

Observers are invited to apply for time using SHOC on the 1.9-m, 1.0-m and 0.75-m telescopes. Those new to SHOC must request assistance for the first night of their run; students must be accompanied by their supervisor.

Further information

Further information can be found on the SHOC commissioning website.  A user manual is available here.