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:

• UFTI 0.09 – gf20070725_10_mos.sdf — [GIF]
• UIST 0.06 – gu20070725_20_mos.sdf — [GIF]
• UIST 0.12 – gu20070725_14_mos.sdf — [GIF]

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

Depth and Image Quality Comparison (K-band only)

Camera	Pixel arcsec)	FWHM (arcsec)	ZP (mags)	Throughput	Background counts (per arcsec)	Mag error on 17th mag star in 150sec
UFTI	0.09	0.55	22.3	34%	30,860	0.44
UIST 0.06	0.06	0.68	21.8	23%	16,940	0.45
UIST 0.12	0.12	0.66	21.7	21%	15,350	0.50

• 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.