We feature "FOCAS First Light" in this March issue of Subaru This Month.

FOCAS (Faint Object Camera And Spectrograph) is an instrument installed at the Cassegrain focus of the Subaru Telescope. FOCAS is about 2 meters wide and weighs about 2 tons. FOCAS detects visible light coming from celestial objects in one of two modes: "imaging" and "spectroscopic". It can quickly switch between the two modes via computer control.

Four foci of the Subaru Telescope

After transportation from Japan, FOCAS was attached to the simulator in the Simulator Lab at the Hilo facility and underwent a careful examination. When we confirmed that all systems were working normally, FOCAS was loaded onto a truck and taken to the 4200-meter summit of Mauna Kea. Upon its arrival, the truck was backed up the last slope to the Subaru Telescope enclosure.

FOCAS attached to the simulator

During the transportation work to the summit

The truck loading FOCAS and the Subaru Dome

FOCAS passed a final inspection and was mounted at the telescope's Cassegrain focus on February 1.

FOCAS attached to the Cassegrain focus of the Subaru Telescope

FOCAS waiting for observation

On the night of February 2, light coming from a star was gathered by the Subaru Telescope and led into FOCAS, marking the instrument's moment of "First Light". This was followed by 5 nights of successful test observations.

There are plans to use FOCAS to continue observing the "Subaru Deep Field" (SDF), which was first observed with CISCO. FOCAS would be used to obtain spectra of the faint galaxies. The observations would allow us to estimate the physical parameters (like temperature and density) for the objects in the SDF. We will be reporting the results from FOCAS on the Subaru Telescope website.