SAAO - South African Astronomical Observatory

The Alan Cousins Telescope - Automatic Photometric Telescope

The ACT was commissioned in mid-2000 and has been running for over two years now with good results. We are continuing with upgrades to the system, but it is now available for use by the South African astronomical community and applications for telescope time are encouraged.

The name of the telescope honours the life and work of Dr A.W.J.Cousins. We feel that this is particularly appropriate, given Alan's long interest in accurate photometry and his particular interest in this telescope.

Application for data

There is no "formal" application form or procedure but we would ask that you submit the following when requesting time:

  • A concise and SHORT "justification" of the science.

  • A list of target stars - with accurate co-ordinates (and epoch !) - indicating which (if any) local comparison stars should be attached to which target stars. Also, indicate which filters are required (currently only UBVRI are available) and the integration times. The latter can be left to us to choose, if you wish - in some cases we might have to do this (see below).

  • If a project is accepted, then we would appreciate finding charts from some sensible source - the standard output from the Digitised Sky Survey is very good (see, for example, the links page of the SAAO web site or In fact, we would much prefer to have .fits files from Ledas, as we are in the process of trying to produce "template" fields from these files rather than at the telescope.


Please try to keep the following in mind:

  • Because we can't easily assess data quality by looking at the incoming data as it arrives, all data are acquired in a "symmetric" sequence (eg VBURIIRUBV + UBVRI_sky). There are a limited number (10) of filter programmes available (typically UBV or UBVRI with different integration times) so you might not get exactly what you ask for, though we will try.

  • The current bright limit of the system is about 7th magnitude - but remember that a very red star at 7 mag will overload the system at R and/or I, for example. We're not sure what the faint limit is - certainly the system will find and measure a star at 12 mag - probably quite a bit fainter than that, though we haven't done exhaustive tests.

  • This is currently (and for the forseeable future) a photomultiplier system. It's worse than such a system would be with a human operator because it uses a fixed (scanning) method of centering the star in the aperture. Crowded fields therefore can be a problem; a target star with a "companion" closer than about 30 or 40 arcseconds is unlikely to work.

  • With the current method of operation, and serving three separate institutes, the ACT is best used for stars which require observations at a rate of once per night - for example, variables with periods of a few days or longer; variables for which the data can be easily phased, and so on. It is not (at present) suitable for "high speed" observations, for example, though during the "commissioning" phase, we have set the system to observe one star essentially all night (in a Comp, Var, Var, Check, Var, Var, ... type of mode) and that worked well. Special arrangements would have to be made for such proposals.

    During 2002, we have tried obtaining data from the (non-science-quality) CCD which is used for acquisition/target identification and, although data analysis is at an early stage, it seems likely that the system can achieve about 10% accuracy, which might be useful for some forms of work (currently the system has observed CVs to detect "outburst" phases, for example) . At present, we do not have a data "pipeline" for such CCD frames, and flat-fields are a problem, but if people want to submit requests for such data, we will try to accommodate them.

  • If you submit a large list of targets, and the proposal is accepted, please expect that these will be done over a period of time and not all at once - or that only a sample will be done - so, listing the priorities of your targets would be helpful . Again, the speed at which data can be obtained will depend on demand for time.

  • At present we are reducing all photometry via the same sort of "pipeline" that we use for the data from the 0.5m telescope. We are providing "users" with fully reduced data in a form (HJD + photometry) for targets (plus comparisons, if observed). If this is not acceptable (eg you wish to reduce your own data) you should discuss this with Dave Kilkenny.

Examples of programmes which have been or are currently being run include:

  • Part of a multi-site campaign on the Helium star HD160641 (Kilkenny et al)
  • Rotation periods of roAp stars (Martinez/Handler)
  • Long term monitoring of RCB stars (Crause/Kilkenny)
  • Light curves of UMa stars (Cunow/Smits)
  • Long-term monitoring of Extreme Helium and HdC stars (Kilkenny)