SALTICAM Current Status

As of the call for 2012 Semester I proposals, SALTICAM is functioning in the standard modes. Amplifier 4 has been flaky, mostly being completely dead, but this is expected to be fixed soon (certainly before the next semester). Though guiding with SALTICAM is possible, it has several features making it not useful for many applications (see Section 6.6 of the call for proposals). Overall, we suggest limiting SALTICAM exposure times to approximately 120 seconds with open-loop tracking.

All SALTICAM sensitivity calculations for planning observations should be done with the newest version of the SALTICAM Simulator.  For quick reference, some count rates for SALTICAM are given below in Table 4 from the  call for proposals. The numbers are based on recent throughput tests with a burst mirror, as well as Sloan comparison fields, and have been extrapolated for a typical pupil during a track.

The count rates and signal-to-noise ratio numbers can be extrapolated to other exposure times and fainter/brighter targets. We have directly verified count rates up to about 5 minute exposures and these behave as expected. Longer integrations are not practical due to the difficulties with auto-guiding and SALT’s current open-loop tracking performance. Thus, the deepest SALTICAM exposures should ideally be constructed from dithered and co-added ~2 minute exposures. Whether the ideally scaled signal-to-noise ratio is reached depends on e.g. the quality of flat-fields and the stability of the PSF of sources over tens of minutes (c.f. the current lack of active segment alignment). Therefore, we urge the PIs to be conservative in estimates of deep SALTICAM imaging until proper characterisation has been obtained.