Globular Cluster NGC 6934

Technical information - Infrared Image

Instrument: The observations were obtained with the University of Hawaii Adaptive Optics System (Hokupa'a) with the infrared camera QUIRC. Hokupa'a is a 36-element curvature-sensing AO system. The Insitute for Astronomy, University of Hawaii, Adaptive Optics Group has more information about the AO system. The detector in QUIRC is a Rockwell 1024 x 1024 pixel HgCdTe "HAWAII" array sensitive to 2.5 microns. A description of QUIRC is available from the Insitute for Astronomy.

Pixel scale: 0.01974 arcsec per pixel (Detector pixels)

Field of view: 20.4 arcsec x 25.5 arcsec

Information about filters, exposure time and resolution:

Filter: K-band (2.2 µm broad band)
Exposure time: 23 min 35 sec
Resolution (FWHM): 0.09 arcsec

The images were taken as individual exposures with exposure times of 10 seconds or 15 seconds. The limiting magnitude is approximately K=21.3 mag (5sigma detection).

Processing: The images were sky-subtracted using sky images obtained before and after the observations. Then the images were registered and co-added.

The images were then processed with a filtering method that suppresses the PSF halo characteristics of partially compensated AO images. This consists in a simple, linear filtering of the image in the Fourier space, based on an empirical analysis of the properties of AO compensated images. It does not affect the core of the PSF, the airy rings nor possible PSF artifacts. To first order, the resolution is therefore the same as in the unfiltered images.