Hokupa'a Data Reduction

The Data Reduction pages are still under development and are intended to highlight the data reduction issues specific to Hokupa'a and QUIRC. Some relevant information can be found at the summary of the US Gemini Project Office workshop on the reduction of Gemini AO data held Feb 26-27, 2001 in Tucson. There are currently three areas of information: Photometry, Astrometry, and example data sets.

Introduction:

When dealing with AO corrected images special attention should be given to the shape and variation of the point spread function. By nature the adaptive optics correction varies with time causing instabilities in the form of the PSF. This effects the shape and amount of energy in the core and extended halo of the PSF. These have a number of effects. First, a significant portion of the point source energy is in the halo of the PSF. This can strongly affect the quality of the photometry from AO images for point and for extended objects. Second, while the core the PSF will be considerably sharper, the ability to detect close objects also depends on the contrast between the fainter objects in the halo of the brighter object. This effect is particularly important when finding objects in crowded fields. Finally, since the AO PSF varies across the field, all of the above must be considered with position in the field.

Photometry:

As mentioned the photometric accuracy depends on knowledge of the shape and variations (with field position and possibly time) of the PSF. We have begun studying the effect of the AO PSF on photometric accuracy for point sources and extended objects. Check out the Hokupa'a Photometry page for information.

Astrometry:

Given the increased resolution of Hokupa'a, the astrometric accuracy is improved. For information check out the Hokupa'a Astrometry page written by Francois Rigaut.

Example data sets:

There are a number of data sets, taken as part of the system verification or engineering, that are available for download. Check out the public and system verification data sets on the Gemini Data page.

Also check out real PSFs on the PSF library page.

Last update 14 March 2001; Mark Chun