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WFC Related Information


  1. INT-WFC system responses
  2. INT-WFC - SDSS photometric transformations
  3. INT-WFC - Bad Pixel Maps
  4. INT-WFC CCD3 Vignetted Corner
  5. TELFOCUS in the WFC Headers
  6. Acknowledgements

1. INT-WFC system responses

The system responses of the INT-WFC were modeled recently by Bell, Naylor et al. (2012), being published in the paper "Pre-main-sequence isochrones - I. The Pleiades benchmark" (2012MNRAS.424.3178B).

The model includes the cumulative effects of the transmission of the Earth’s atmosphere, the reflectivity of the telescope mirror, the transmission of the prime focus corrector optics, the quantum efficiency of the detector and the filter transmission.

The table data also available at the authors website (filters u, g, z, i and r).

2. INT-WFC - SDSS photometric transformations

The same paper of Bell, Naylor et al. (2012) (2012MNRAS.424.3178B) gives magnitude and colour differences between the standard Sloan Digital Sky Survey (SDSS) and the natural INT-WFC photometric systems. The study include the standard SDSS system responses and the calculated INT-WFC responses, folding atmospheric models through both.

Data table available also at this author website. See also their related Pleiades page.

3. INT-WFC Bad Pixel Maps

Like any older or newer camera, WFC is not perfect. The following bad pixel maps were obtained by dividing two dome flats taken in 2014 at high and low signal, then running the IRAF badpix task. They could be used to correct each CCD of the WFC bad pixels:

  • WFC Bad Pixel Maps (sigma 10 - fainter)
  • WFC Bad Pixel Maps (sigma 5 - stronger, recommended)

    4. INT-WFC CCD3 Vignetted Corner

    It is known that a very small corner of the upper-left CCD3 is vignetted. The following mask holds 1 for good pixels and 0 for bad pixels and could be used in IRAF to disregard the vignetted corner.

  • WFC CCD3 corner mask (.pl file)

    5. TELFOCUS in the WFC Headers

    For some unknown reason probably associated with some feature of the old TCS or ICS software, the value of TELFOCUS seems to be changing as recorder in the WFC headers (up to about 0.1 mm) for the same filter. We tested this apparent problem in 2017 (FR 22542) and we concluded that the actual focus mecanism performs as expected (remaining steady within 0.01mm).

    5. Acknowledgements

    Thanks are due to Dr. Tim Naylor and his former PhD student Cameron Bell (Exeter Univ, UK) for providing the INT-WFC system responses and SDSS photometric transformations.

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    Contact:  (WFC Instrument Specialist)
    Last modified: 29 December 2023