MACHO Camera System

Chris Stubbs from U. Washington next to the MACHO camera

We have developed an astronomical imaging system that incorporates a total of eight 2048x2048 pixel CCDs into two focal planes, to allow simultaneous imaging in two colors. Each focal plane comprises four ``edge-buttable" detector arrays, on custom Kovar mounts. The clocking and bias voltage levels for each CCD are independently adjustable, but all the CCDs are operated synchronously. The sixteen analog outputs (two per chip) are measured at 16 bits with commercially available correlated double sampling A/D converters. The resulting 74 MBytes of data per frame are transferred over fiber optic links into dual-ported VME memory. The total readout time is just over one minute. We obtain read noise ranging from 6.5 to 10 electrons for the various channels when digitizing at 34 Kpixels/sec, with full well depths (MPP mode) of ~100,000 electrons per 15 micron by 15 micron pixel. This instrument is currently being used in a search for gravitational microlensing from compact objects in our Galactic halo, using the newly refurbished 1.3 m telescope at the Mt. Stromlo Observatory, Australia.