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Instrumentation Status for the AAT

General Information

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

Queries can be directed to the relevant instrument scientists. These are (usernames in brackets - all email should be sent to user -@- aao.gov.au):

Instrument News for Semester 09A applicants


Status of Common-User Instruments


AAOmega + 2dF Multi-Object Spectroscopy

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 the reduced data are also available.

The throughput of both the red and blue cameras of AAOmega has recently been re-determined, and the AAOmega MOS S/N calculator updated to reflect this. All applicants should re-determine their exposure times accordingly.

Depending on the complexity of the field configuration and the number of fibre moves required, applicants can expect up to 7.5 seconds to position a single fibre, and that each field will require a minimum of 1hr15min, including overheads.

An alternate dichroic, procured by the WiggleZ team and the AAO, is now 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 ~9500 Å. The dichroic change occurs over +/-200 Å. The 5700 Å dichroic is of exceptional quality, with a smooth monotonic changeover, while the 6700 Å is smooth, but not monotonic. Additionally, there are two 20% troughs in the reflected beam at 4815 and 4905 Å. The optics are in a slowly converging beam and so these features are not removed by a simple flat field observation. A local averaging option in the 2dfdr software alleviates the problem somewhat. Applicants considering using the 6700 Å dichroic should contact Rob Sharp before applying, and then indicate their choice in their proposal and Instrument Request Form.

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" or better. AAOmega+2dF field plates have 8 guide fibres and 392 science fibres. Mean sky fibre subtraction has achieved residuals as low as 1%, so observers considering the use of Nod & Shuffle or Cross-Beam Switching techniques should discuss their needs with Rob Sharp prior to submitting their proposal, to ensure that the extra workload for the user, and significant exposure time overheads (factors of between sqrt(2) and 4, depending on N+S mode) 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 no later than one month before the scheduled observing run. Failure to do so may result in forfeiting the allocated time.

Further details about the capabilities of AAOmega in 2dF MOS mode are available, as well as a list of available gratings.

UK applicants please note: As with previous STFC policy, Travel and Subsistence (T&S) will not normally be awarded for AAOmega 2dF MOS time allocated by AATAC to UK-based PIs. Observations for UK-based applicants (i.e., those normally supported by STFC) will be conducted by the 2dF/AAOmega Fellow or other AAO staff. However, where the number of UK nights to be carried out by the 2dF/AAOmega Fellow in a semester is too large, or a compelling case can be made that real-time interaction with the applicant at the telescope would strongly benefit the efficiency or success of the program, the Deputy Chair of AATAC may recommend T&S support where appropriate. UK-based applicants who wish to be considered for such support should indicate this in Section 5 of the AATAC application form, and must justify their request in the technical case of the proposal. Requests for T&S after the schedule is released will not be considered. T&S for AAOmega/2dF is still expected to be the exception rather than the norm, and the final decision on whether such support can be offered rests with the Chair of PATT.

AAOmega + SPIRAL Integral Field Unit

AAOmega is a dual-beam, bench-mounted spectrograph which can also be used with the SPIRAL IFU at the Auxiliary Cassegrain focus. The SPIRAL Integral Field Unit (IFU) is a 512 element fibre feed to AAOmega, and permits 3D spectroscopy over a field-of-view of 22.4 x 11.2 arcsec at a spatial sampling of 0.7 arcsec. Science Verification results can be found in the August 2006 AAO Newsletter.

The throughput of both the red and blue cameras of AAOmega has recently been re-determined, and the AAOmega IFU S/N calculator updated to reflect this. All applicants should re-determine their exposure times accordingly. Users should note the U band sensitivity is comparatively poor due to components used in the construction of the SPIRAL IFU.

An alternate dichroic, procured by the WiggleZ team and the AAO, is now 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 ~9500 Å. The dichroic change occurs over +/-200 Å. The 5700 Å dichroic is of exceptional quality, with a smooth monotonic changeover, while the 6700 Å is smooth, but not monotonic. Additionally, there are two 20% troughs in the reflected beam at 4815 and 4905 Å. The optics are in a slowly converging beam and so these features are not removed by a simple flat field observation. A local averaging option in the 2dfdr software alleviates the problem somewhat. Applicants considering using the 6700 Å dichroic should contact Rob Sharp before applying, and then indicate their choice in their proposal and Instrument Request Form.

Further details about the capabilities of AAOmega in SPIRAL IFU modes are available, as well as a list of available gratings.

IRIS2

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, and K-bands at R~2400 can be carried out. All standard imaging, and point-source spectroscopy data are pipeline-processed by the ORAC-DR system.

Due to current difficulties in reliably positioning the coldstop wheel, potential applicants with programs which require the use of the Z, He I, Fe II, Pa-beta, Jcont, or Hcont filters should contact Paul Dobbie prior to submitting their proposal.

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 Paul Dobbie 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 Paul Dobbie with any queries.

UCLES

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 now controlled by an integrated Linux/VME-based GUI. Besides enhanced reliability, this new control system offers users the ability to implement sequences for configuring the spectrograph, and taking exposures. Observers can also slew the telescope themselves, from their own target lists or by querying on-line databses. Information on this new interface is available in the ODC Users Guide in the UCLES Cookbook. Prospective UCLES users should contact the instrument scientist, Stephen Marsden, for more information.

UHRF

The UHRF is a separate échelle spectrograph located in the same coudé room as UCLES. It offers ultra high resolution over very small spectral regions, using an image slicer in place of the slit. UHRF is generally used with the EEV2 detector, at 3E5, 6E5, and 1E6 resolving power. The MITLL3 CCD cannot be binned, so is less suited to UHRF except when fringing of the EEV2 detector in the red may limit the S/N achievable (contact Stephen Marsden for further information). Note that it is also possible to observe at 100,000 resolution directly through a 0.6 arcsec slit at 3E5, with a 4-5x gain in throughput over the use of the image slicer, depending on the seeing. Because UHRF's image slicer comes after the 1.5" square entrance aperture, UHRF throughput is rather more seeing-dependent than UCLES.

Both UHRF itself, and the attached CCD detector, are now controlled by an integrated Linux/VME-based GUI. Besides enhanced reliability, this new control system offers users the ability to implement sequences for configuring the spectrograph, and taking exposures. Observers can also slew the telescope themselves, from their own target lists or by querying on-line databases. Information on this new interface is available in the ODC Users Guide in the UHRF Cookbook. Prospective UHRF users should contact the instrument scientist, Stephen Marsden, for more information.

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 -@- aao.gov.au), even if that instrument has been used previously.
Note that with effect from Semester 08A, WFI is no longer available as either a common user or as a visitor instrument on the AAT.

Return to AATAC Applications page
Heath Jones, aatac -@- aao.gov.au