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Wide Field Imager (WFI)

AAT Instrument. WFI is a decommissioned facility and is no longer offered or supported at the AAT. The following information is provided for historical completeness.

In Brief: Wide Field Imager (WFI - pronounced "wiffee") is an 8K x 8K CCD mosaic for optical imaging at the AAT prime focus.  It mounts on the upgraded Prime Focus Unit (PFU), which provides a 6 position filter wheel and two-travelling-blade shutter capable of exposures as short as 2 seconds with 1% uniformity.

WFI is not controlled by the AAO's standard observer interface, but by the ANU's CICADA interface. For sky-limited programs, multiple exposures of 5-10 minutes are recommended. Scripting to control multiple exposures with telescope dithering is available. There are significant overheads in guiding (2-3 minutes per exposure), so it is only recommended for programs which are not sky-limited in 5-10 minutes (i.e. U-band imaging).

WFI is a shared instrument which is used on both the AAT and the ANU 40" telescope on Siding Spring. While every effort will be made to interface WFI's controllers to the AAT's computer system, no guarantee can be offered that the instrument will perform as well as the AAT's facility instruments. Observers must have prior experience with WFI, and require permission from both the AAO Director, and from RSAA, before applying to use WFI at the AAT.

Instrument Scientist: No Instrument Scientist at present. Contact Head of Astronomy for information.
WWW Page: Wide Field Imager Prime Focus Upgrade WWW Page
Documentation: WFI Cookbook and WFI Performance (and old AAO CCD Imaging Manual)
Other Info: RSAA WFI Page
S/N Calculator: Direct Imaging Calculator

Fact Sheet:

Detector: Eight 2048x4096 15um square pixel MIT/LL CCDs arranged into a 8192 x 8192 pixel mosaic. WFI suffered a major vacuum failure in June 2004, which was repaired by RSAA. However, it was found that on completion of the repair, two of WFI's 8 CCDs were not working. One CCD has since been fixed, but another remains out of use. The inoperative CCD is No. 7, where the layout of CCDs is:
5 6 7 8
4 3 2 1

(see this link for a detailed layout).

Focal Station: Mounted at prime focus f/3.3 with triplet corrector (doublet only available on special request). 
Image Scale: 0.2295 arcsec/pixel
Filters: U,B,V,R and SDSS g,r,i,z filters are standardly available for all programs. Other (smaller) AAO filters can be used, but will vignette the field and may require the preparation of special filter holders. Observers must request such special filters well in advance, and contact their support astronomer well before their run to organise their preparation.  Observers can use their own filters, but will need to provide a detailed specification once time is allocated, and provide the filters themselves 6 weeks before their run, so that special holders can be manufactured for them. See the AAO Filter Catalogue and the WFI/PFU WWW Page for further information.
Sensitivities: Direct Imaging Calculator