Hokupa'a Performance and Use

Status and availability:	Hokupa'a was used at Gemini North from 2000B until 2002A and has now been superceded by Altair.
Operational use:	Hokupa'a feeds its own near-IR camera (QUIRC). The basic requirement for use of Hokupa'a is a suitable wavefront reference source (guide star). The final image quality obtained by the system depends strongly on the characteristics of the guide star. Basic considerations can be found in the Hokupa'a Guide Star Requirements. As the performance is variable (depending on the atmospheric conditions at the time of the observation), a calibration point-spread function may be necessary for the data analysis. Issues to consider can be found in the Point Spread Function calibrations page.
Performance:	The performance achieved by Hokupa'a depends on many factors. Foremost it will depend on the intrinsic seeing at the time of the observation, telescope windshake, the wavelength and airmass of the observation, and the characteristics of the wavefront reference source (the guide star). In addition how these factors combine to affect the performance depends on which performance criteria (e.g. FWHM, Strehl, or 50%EED) you are interested in. A simple image quality calculator (IQC) that combines these characteristics is also available. Actual PSFs obtained as PSF calibration observations can be found in the PSF Library page. The system performance within this parameter space was simulated using a complete AOS simulation package written by Francois Rigaut. See the details on the Hokupa'a system performance for how to estimate the performance on your target based on the guide star brightness, field angle, and zenith angle. Estimates of the photometric accuracy that can be expected via PSF-fitting photometry with model and empirical PSFs are to be added.
Sensitivity:	Based on simulated PSFs, the 5-sigma 1-hr limiting magnitude within a 50% EED aperture at J, H, and K is about 1 microJansky. For more detailed point and extended source values see the Hokupa'a Sensitivity page.
Observing:	Information on the observing process can be found in the introductory Observing page and in the Hokupa'a/QUIRC Observing manual. Current estimates for observing overheads are that each new target will incur an overhead for setup, instrument configuration changes, and detector readout. For details refer to the Hokupa'a Observing overheads page.
Calibration:	In addition to the usual near-infrared calibrations, observations of a Point Spread Function calibration may be required for data processing of adaptive optics images. There are a number of issues to consider in obtaining a useful PSF calibration. Please check out the Hokupa'a Calibration and the Data Reduction pages for information. Information, catalogues and a search engine for photometric standard stars are available.
Data processing and software:	A Hokupa'a/QUIRC package of IRAF scripts for basic image processing has been released as part of the Gemini IRAF package. Data reduction issues specific to Hokupa'a can be found in the Data Reduction page.

Last update 22 February 2002; Phil Puxley
In original form; Mark Chun