UIST: Engineering: UIST/UFTI Comparison – July 2007

UIST: Engineering: UIST/UFTI Comparison – July 2007

Observations of the same FS standard, FS146, were secured on 2007-07-25, with UFTI (0.09″ plate scale), UIST 0.12″ and UIST 0.06″. The same exposure time, number of coadds and jitter pattern (10sec x 3 coadds x 5pt jitter) were used in each case. The same K98 filter was used. Data were reduced with the same 5-point jitter pattern recipe.

The mosaics are available here:

The telescope was focused before each 5-point jitter pattern (see log below).

Depth and Image Quality Comparison (K-band only)

ThroughputBackground counts
(per arcsec)
Mag error on 17th mag
star in 150sec
  • FWHM derived from gaussian fits to same four stars in each reduced mosaic.
  • Z.P. calculated with same 5″ aperture, centred on FS146.
  • Throughput calculated from the zeropoint: ZP = 2.5 log[P*thruput/gain], where P is the photons/second from zeroth mag star, corrected for atmosphere, filter and effective 3.5m diameter of UKIRT (P = 1.35e10 photons/sec at K). Gain for UIST and UFTI are 6.0 and 5.5, respectively.
  • Background counts: counts on sky per arcsecond (equivalent to throughput provided sky brightness doesn’t change).
  • 17.0 mag star errors:Faintish source near center of each mosaic – errors given by GAIA Aperture-photometry tool in 2.5 arcsec aperture.

Qualitative comparison

The images below show a comparison of the UIST 0.12″ camera and UFTI of the same region (50″ NNE of FS146; not covered by the UIST-0.06″ camera data).

FS146 as seen by UIST 0.06, 0.12 and UFTI. The central black contour outlines the FWHM.