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Applying for time


More about ACAM

For ING staff

Chris Benn
ACAM Instrument Specialist

ACAM - auxiliary-port camera


ACAM (Auxiliary-port CAMera) is mounted permanently at a folded-Cassegrain focus of the 4.2-m William Herschel Telescope. It can be used for high-throughput broad-band imaging, narrow-band imaging and low-resolution spectroscopy.

The field of view in imaging mode is 8 arcmin (0.25 arcsec/pixel). The Sloan u g r i z broad-band filters are usually present in the filter wheels, but almost any of ING's filters can be mounted in ACAM.

Low-resolution spectroscopy over ~ 3500 - 9400 A is provided by a VPH disperser. For 1.0- and 0.5-arcsec slits, the on-axis spectroscopic resolutions at 6000 A are R ~ 450 and 900 respectively. At 7000 A, the throughput of ACAM is a factor ~ 1.5 times higher than that of ISIS.

ACAM, like its predecessor (the aux-port camera), is available whenever a prime-focus instrument is not in use, so is well-suited to observing override programmes and targets of opportunity.


2019 November: The shutter and filter-wheel problems noted below were addressed during the recent standdown, and further problems are not expected. In addition, the feedback to the observer about wheel movements has been improved - if the wheel for some reason does not arrive at the correct position, an error message will be displayed at the instrument-control interface.

2019 February (updated August 2019): During the last year, there have been occasional (~ once a month) problems with the positioning of two mechanisms: (a) filter wheel 2 and (b) the CCD shutter. It's expected that these problems will be addressed when ACAM comes off the telescope for servicing in autumn 2019.

Regarding (a) filter wheel 2, we recommend that observers about to embark on long science exposures, after movement of wheel 2, first take a short (few-sec) test exposure.

Regarding (b) the shutter, we recommend that observers keep an eye on the counts being obtained from targets of known apparent magnitude, and warn the telescope operator if they appear unusually low (the operator can then check from engineering control the true status of the shutter).

2015 July: Script autoflat available to take sky flats through specified series of filters.

2014 April: Dither scripts multdither and mcol now available.

2013 December: 27-arcsec slit now available (useful for minimising differential losses between target and comparison star).

2012 October: Quick-look spectroscopic extraction available.

2011 May: Sloan u, z (and new g, r, i) filters now available.

2011 February: Sloan u filter (ING filter #700) delivered (z and new g r i still to come).

2011 January: Transmitted wavefront errors measured for most filters.

2010 November: GG395 and GG495 order-sorting filters now available, for use with the VPH disperser.

2010 October: Target-acquisisition tool commissioned, for use with spectroscopy mode.

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Contact:  (ACAM Instrument Specialist)
Last modified: 21 November 2014