A versatile new high-throughput imager and spectrograph, ACAM, was successfully commissioned on the William Herschel Telescope in June 2009, and is now available for use by the astronomical community.

ACAM was designed entirely by engineers and astronomers at ING, and was built in collaboration with Kevin Dee of Engineering & Project Solutions Ltd.

ACAM first-light image of spiral galaxy Messier 51. This is a composite of images through several different filters, with red colour highlighting regions where new stars are forming. The circular field of view is 8 arcmin across (about one quarter the angular diameter of the moon). Credit: Pablo Rodríguez-Gil, Chris Benn, Andrew Cardwell. [ JPEG ].

ACAM can be used either for imaging (as above) through broad-band or narrow-band filters, or for taking spectra. In spectroscopy mode, the light from the object under study is dispersed by a VPH (volume-phase holographic) grating. For a 0.5-arcsec slit, the on-axis spectroscopic resolution is approximately 900 at a wavelength of 6000Å.

ACAM is mounted permanently at a folded-Cassegrain focus of the telescope, and can be deployed at a few minutes notice. This allows astronomers to switch quickly from the main camera in use for the night, to ACAM, for rapid follow-up of unusual events.

ACAM's exceptional versatility will allow astronomers to carry out a broad range of high-impact science projects which otherwise would not be possible with the WHT, in particular those requiring one or more of: rapid response; narrow-band imaging; wide field of view; low-resolution spectroscopy; or high camera throughput (very litte light is lost in the optics). Example projects include:

• Rapid follow-up of distant supernova explosions and gamma-ray bursts, to investigate the physics of these violent events.
• Studies of large planets outside our solar system, e.g. time-series imaging of the host stars to search for changes in orbital periods hinting at the presence of earth-sized planets.
• Narrow-band imaging of low-redshift galaxies, to discover where in galaxies the formation of new stars takes place.
• Initial spectroscopic investigation of very faint objects discovered serendipitously with other WHT instruments.

ACAM being craned up to the WHT. Credit: Javier Méndez (ING). [ JPEG | TIFF ].

ACAM, now mounted permanently at one of the folded Cassegrain foci of the WHT. Credit: Javier Méndez (ING). [ JPEG | TIFF ].

Some of the ACAM team at the telescope: Domingo Alvarez, Carlos Martin, Renee Pit, Kevin Dee, Diego Cano, Tibor Agocs, Juerg Rey, Sevando Rodriguez, Alan Chopping, Roberto Martinez. Credit: Kevin Dee. [ JPEG ].

The ACAM first-light team: Carlos Martín, Craige Bevil, Tibor Agocs, Kevin Dee, Chris Benn, Andrew Cardwell, Pablo Rodríguez and Don Abrams. Credit: Pablo Rodríguez (ING). [ JPEG | TIFF ].

More information:

• First-light images
• ACAM web pages