Comparison of VISTA with other Wide Field Imaging Facilities
(compiled 2000, July 01)

Below I tabulate various wide field imaging facilities in the world compared to VISTA. All the major optical imaging cameras with fields of view greater than 0.5deg$^2$ are included. In the optical I include the INT, WHT and Gemini for comparison. Similarily in the IR I include, INT, WHT, Gemini and UKIRT+UFTI. These tables show where VISTA will perform relative the other facilities in 2004 and how VISTA represents a factor of 10+ improvement on current UK capabilites.

In the optical VISTA is a factor of two better than any competitor. In the IR the nearest competitor is VLT-UT4 and the NIRMOS instrument. Note NIRMOS will not function in K. Note that the survey power of VISTA that is quoted is based on the fraction of the focal plane that is covered with IR detectors. Thus in principle we can increase the survey power by a factor of 1.8 if we could fit in 16 detectors rather than the the planned 9. Note also if we decrease the pixel size in VISTA from the nominal 0.30" to 0.25", the grasp of VISTA will drop below the grasp of UKIRT+WFCAM. However, not that that in seeing better than 0.8, VISTA will perform better than WFCAM for unresolved sources.

In the case of the optical the typical pixel size is 0.3" or less and except in the case of SDSS will sample seeing of 0.7" with two pixels or better. However in the IR the range of pixels sizes is large extending up to 2.0" in the case of 2MASS. To make the IR comparison one needs really needs to take the sampling into account in the background limited regime.

Comment on the Shape and Size of the Field of view

When one is camparing the capabilities of the different facilities it is important to realise that the size of the field of view can be be weighted too highly. e.g. if one wants to image a series of disconnected XMM or Chandra fields then a field of view more that 20'x20' gives no further advantage.
  • In the the case of VISTA, this is particularly relevant in the optical but not in the IR.
  • In the case of Sloan one the camera focal plane is deivided into 5 strips, one of each waveband with a gap of 1 CCD between each chip. Therefore to get a contiguous image requires at least two images. In addition in drift scan mode only 1/5 of the 'time' is given to each filter. This has the advantage that you get all 5 bands(ugriz) simultaneously but one cannot obtain longer exposures in a single band.
    Optical Survey Power Comparison
    Telescope Country Aperture Detector "/pixel FOV(deg²) A-Omega Grasp date
    . . . . . . . . .
    VISTA UK 4.0m 20kx20k 0.25 1.39degx1.39deg
    1.92deg²     		24.1 - 2004-Q1
    CFHT-MegaPrime US-Fr-Can 3.6m 18kx18k 0.21 1.05degx1.05deg: 1.10deg² 11.2 . 2001-Q2
    BLT-WFI US-Germany-Italy 8.0m 8kx8k 0.2 0.44degx0.44deg
    0.20deg²     		9.9 - 2003-Q2
    Subaru Japan 8.2m 8kx10k 0.15 0.33degx0.42deg
    0.14deg²     		7.4 . 2000
    SDSS US 2.5m 10kx12k 0.40 1.11degx1.33deg
    1.48deg²     		7.3 . 1999
    MMT-Megacam US 6.5m 18kx18k 0.08 0.40degx0.40deg
    0.16deg²     		5.3 . 2001-Q2
    VST ESO 2.6m 16kx16k 0.21 0.93x0.93deg
    0.87deg²     		4.6 . 2002-Q?
    NOAO-Mosiac US 4.0m 8kx8k 0.26 0.58degx0.58deg
    0.33deg²     		4.2 . 1999
    CFHT-12K US-Fr-Can 3.6m 12kx8k 0.20 0.33deg² 3.4 . 1999
    ESO 2.2m ESO 2.2m 8kx8k 0.24 0.53degx0.53deg
    0.28deg²     		1.1 . 1999
    WHT UK-NL 4.2m 4kx4k 0.25 0.28degx0.28deg
    0.08deg²     		1.1 - 1999
    INT UK-NL 2.5m 6kx4k 0.33 0.55degx0.37deg
    0.20deg²     		1.0 . 1998
    VLT + VIMOS ESO 8.0m 8kx8k ? ? ? . 2000-Q3
    Gemini(N)- GMOS US-UK-Can 8.0m 4kx4k 0.10 0.11degx0.11deg
    0.012deg²     		0.61 . 2001-Q1
    Note:
    1. The grasp column includes an allowance for the seeing. (see below for further details.
    2. Gemini + GMOS is included just as an example
    Comparison of Various Near Infra-Red Survey Facilities
    Telescope Country Aperture Detector "/pixel FOV(deg²) A-Omega(m² deg²) Grasp date
    . . . . . . . . .
    VISTA UK 4.0m 6kx6k 0.30" 0.5degx0.5deg
    0.25deg²     		3.14 - 2004-Q1
    VLT+NIRMOS ESO 8.0m 4kx4k 0.21" 0.23degx0.23deg
    0.054deg²     		2.71 - 2002-Q1
    (JH only)
    UKIRT+WFCAM UK 3.8m 4kx4k 0.40" 0.44degx0.44deg
    0.20²     		2.27 - 2003-Q1
    INT + CIRSI UK 2.5m 2kx2k 0.45" 0.25degx0.25deg
    0.062deg²     		0.31 - 1999
    VLT-ISAAC ESO 8.0m 1kx1k 0.147 2.51'x2.51'
    0.00175deg²     		0.088 . operational mid-1999
    WHT + INGRID UK+NL 4.2m 1kx1k 0.25 4.27'x4.27'
    0.0051deg²     		0.070 - 2000
    NTT-SOFI ESO 3.5m 1kx1k 0.292 4.98'x4.98'
    0.0069deg²     		0.066 . 1998
    Gemini- NIRI f/6 US-UK-Can 8.0m 1kx1k 0.116 1.98'x1.98'
    0.0011deg²     		0.055 - 2000-Q4
    UKIRT+UFTI UK 3.8m 1kx1k 0.05 0.85'x0.85'
    0.00020deg²     		0.0023 - 1999
    2MASS US 1.3m(2 of) 3x256x256 2.0" 0.14degx0.14deg
    0.02deg²     		0.080 - 1998
    Notes:
    1. 2MASS has 3 simultaneous IR channels. This is is included in the Grasp column although there is no requirement for many science programs to have more than 1 band.
    2. SDSS observes 5 bands simultaneously so for programs that require a single band this less efficient.
    3. In the Grasp column, I have included a correction for image quality. In the optical I have assumed a floor for the median seeing of 0.7 and in the IR a median seeing 0.5 for the ground based facilities. Where the 2 times the pixel size exceeds this floor, I have used 2 times the pixel size as the image minimum image size.
    Richard G. McMahon <rgm@ast.cam.ac.uk>
    Last modified: Sun Feb 18 18:19:33 2001