CIRSI - Observing Practicalities

Data rates and volumes:

The total read out time for the 4 arrays is around 10seconds. It is intended in the long term that a series of around 10 exposures will be coadded to produce a single image OR if photon rate is sufficiently low longer exposures will be used. Assuming only one image is stored evry 100seconds, the typical data-rate is 8MB every two minutes at 16bits per pixel (0 to 65536).

In a typical 8 hr night the maximum data volume will therefore be 1.92GB. Within IRAF this will double to 3.84GB when the images are stored as floating point reals.

A fully reduced contiguous image produced from 4 interleaved exposures will result in a 4096 x 4096 pixel 64MB image plus ancillary exposure and bad pixel maps.

Observing procedures:

Standard Stars

In an ideal world, there would be UBVRIZJHK photometry of a set of closelt spaced faint standards so that colours terms and extinction could be derived with observations of a single field. Maybe we will set some up. In the mean time there is little overlap between optical and NIR calibration fields. The primary source of NIR standard stars will be:
  • The UKIRT Faint standards [ UKIRT original ] [ local copy ]
  • NICMOS standards
    Information about the NICMOS ground based calibartion program is here
    Photometric data: [ University of Arizona original ] [ local copy ]

    The arrays may have to be windowed down for some of the brighter standards so that so that array does not saturate. The windowed arrays will have a faster read out time then the whole array

    Published by Richard McMahon
    Last modified: Sun Nov 15 09:00:47 1998