Instrumentation Status for the AAT

General Information

The most detailed information on all AAT instrumentation can be found on the AAO Current Instrument Pages.

Queries can be directed to the relevant instrument scientists. These are:

Status of Common-User Instruments

AAOmega + 2dF Multi-Object Spectroscopy

NEW: During 2014, both the red and blue CCDs of AAOmega were upgraded.  In the blue, this has increased the throughput by an order of ~5%, but more importantly, the blue chip is cosmetically much cleaner with only 0.04% of the pixels flagged as bad (compared to 0.8% for the old blue CCD). In the red, the new CCD provides a significant increase in throughput as well as extend the throughput out to ~10,000A. 

AAOmega is a dual-beam, bench-mounted spectrograph for the 2dF top end. Science Verification results with 2dF can be found in the February 2006 AAO Newsletter, and more information can be found in the AAOmega general pages.

Applicants can expect that configuring a single field of 392 science fibres and 8 guide fibres will take around 45min (including overheads) depending on the complexity of the field configuration and the number of fibre moves required.

An alternate dichroic, procured by the WiggleZ team and the AAO, is available to all AAOmega users. This dichroic shifts the transition wavelength between the blue and red cameras from 5700 Å to 6700 Å, and allows full wavelength coverage with the 385R grating right out to ~10,000 Å.

All 2dF MOS applications must pay particular attention to the quality of their astrometry, and should give details about this in their proposal.

AAOmega users considering the use of Nod & Shuffle techniques should discuss their needs with Sarah Brough prior to submitting their proposal, to ensure that the extra workload for the user, and significant exposure time overheads involved, are commensurate with the improvement in data quality.

In order to allow sufficient time for run preparation, all configuration (.fld) files must be forwarded to your Support Astronomer before the scheduled observing run. 

Further details about the capabilities of AAOmega are available from this website.

AAOmega + KOALA Integral Field Unit

The AAO has replaced SPIRAL with the new KOALA IFU feed for AAOmega as of Semester 14A, following commissioning in Semester 13B. Information on KOALA performance can be found in the February 2013 AAO newsletter. 

KOALA (Kilo-fibre Optical AAT Lenslet Array) is a 1000 element fibre feed to AAOmega, a dual-beam, bench-mounted spectrograph. KOALA has a selectable field of view of 24"x18" or 43"x32", depending on the desired spatial resolution (0.7" or 1.25"), an increase in throughput over SPIRAL at all wavelengths, particularly at the extreme blue, and simplified field rotation. An updated exposure time calculator for KOALA will be available shortly. Questions about expected performance should be directed to the KOALA instrument scientist, Andy Green ( 


HERMES is a four-channel, bench-mounted high-resolution spectrograph for use with the 2dF top end. The wavelength ranges of the four channels are fixed at 4715-4900 Å, 5649-5873 Å, 6478-6737 Å and 7585-7887 Å. The spectral resolution is nominally R~28,000, which can be raised to R~45,000 with the use of a slitmask in the spectrograph with ~50% light loss.

All 2dF MOS applications must pay particular attention to the quality of their astrometry, and should give details about this in their proposal. Recent improved mapping of distortions introduced by the gripper gantry have improved the reliability of fibre positioning down to 0.3 arcsec or better. HERMES+2dF field plates have 8 guide fibres and 392 science fibres.

In order to allow sufficient time for run preparation, all configuration (.fld) files must be forwarded to your Support Astronomer no later than one month before the scheduled observing run. Failure to do so may result in forfeiting the allocated time.


IRIS2 is an infrared imager and spectrograph which can be used for either imaging or moderate resolution spectroscopy in the wavelength range from 1.0 to 2.4 microns. The detector is a HgCdTe array of 1024 x 1024 pixel format. IRIS2 is normally used with the f/8 secondary mirror, giving a pixel scale of 0.45"/pixel and a field of view of 7.7' x 7.7'. Broad-band (J, H, Ks and K) and a range of narrow-band filters are available. Both long-slit, and multi-object (using multi-slit masks) spectroscopy (MOS) in the J, H, andK-bands at R~2400 can be carried out. All standard imaging, and point-source spectroscopy data are pipeline-processed by the ORAC-DR system.

IRIS2 MOS makes multi-object observations over the IRIS2 field available for a maximum of three masks per installation of IRIS2 on the telescope. In practice, this translates to a maximum of three masks per lunation, making it optimally suited to deep observations of multiple targets. In the event of multiple proposals exceeding this maximum limit, the usual procedure of preferring proposals with higher grades will be followed. Note that separate masks are needed to observe the same field in H, as in J or K. Prospective IRIS2 MOS applicants should contact Chris Lidman to discuss their requirements prior to submitting a proposal.

Information on the capabilities of IRIS2, including the information required for S/N calculations for imaging and spectroscopy, is provided on the IRIS2 Web pages, or contact Chris Lidman with any queries.


UCLES is a cross-dispersed échelle spectrograph located at the coudé focus, offering a resolution of 40,000-120,000 depending on the slit width and CCD binning. The 79 l/mm grating gives slightly less wavelength coverage than the 31.6 l/mm grating, but offers a longer slit for extended objects, or better sky subtraction on fainter targets. Switching between the two gratings is trivial. The EEV2 2K x 4K CCD should be the detector of choice for most UCLES programs when working blueward of H-alpha (6563 Å). At longer wavelengths, the significant fringing of the EEV2 could be a problem (see the EEV2 Web page), and the MITLL3 detector has better red quantum efficiency in any case (though binning is not possible with the MITLL3).

Both UCLES itself, and the attached CCD detector, are controlled by an integrated Linux/VME-based GUI, which allows automated observing sequences and independent telescope control, among other things. Information on this interface is available in the ODC Users Guide in the UCLES Cookbook. Prospective UCLES users should contact the instrument scientist, Gayandhi De Silva, for more information.

CYCLOPS2: UCLES (with the 79 l/mm echelle only) can be used with the CYCLOPS2 cassegrain fibre-feed to observe single objects. It provides 50% improved resolution over a typical 1" wide slit, along with about 50% higher photon collecting power in typical AAT seeing. Previous issues with instrumental flexure have now been resolved (as of Feb 2011), and flat-fielding and arc calibration strategies are well understood. The UCLES instrument page carries more detailed information on the use of CYCLOPS2.

Visitor Instruments

Proposals for the use of visitor instruments on the AAT are welcome. However. all applicants seeking to use a visitor instrument must first obtain the permission of the Director (director -@-, even if that instrument has been used previously.