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Calibration needs for photometry with wide field imagers

This document outlines critical calibration needs for photometry utilizing wide field imagers, focusing on achieving high accuracy in photometric measurements. Key topics include the significance of simulations, the necessity to match bandpasses, and optimal procedures for data acquisition, processing, and archiving. It proposes strategies for obtaining data, such as dual-dither and jitter techniques, and emphasizes the importance of standardizing measurements to within 1%. Additionally, it discusses effective data handling, from raw observation to final processed images, ensuring reliability in photometric studies of massive stars and stellar rotation.

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Calibration needs for photometry with wide field imagers

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  1. Calibration needs for photometry with wide field imagers Fernando J. Selman • What accuracy? • The importance of simulations • The need to match bandpasses • How should the data be obtained? • How should the data be processed? • How should the data be archived?

  2. Photometric redshifts 5% Stellar rotation: <1% F. Barrientos, PUC Massive stars photometry 1% What accuracy? this depends on the application...

  3. Scatter: dV = 0.034, dB = 0.029, dU = 0.040

  4. Scatter: dV = 0.009, dB = 0.010, dU = 0.014

  5. The need to match bandpasses

  6. simulatedreddening law in the WFI system Fitzpatrick 1999

  7. The WFI system equations

  8. We thus need... - a set of fields at: low airmasses, equator, SCP.-If we can match the bandpasses we need a set of standards, with magnitudes known to within 1%, across the sky, and that is it.- If we can not match band-passes (likely), we need to either: (a) do a full determination of the photometric system: primary and secondary standards, or (b) a set of standard stars with varying luminosity classes, and reddenings, observed in both systems.

  9. How should the data be obtained? Dither Dual-dither Jitter -homogeneity of ctxt map -pixel data from same CCD - e.g. High precision light curves, proper motion of LG dwarfs -complexf ctxt map -couple CCDs - e.g. Precission photometry accros field -designed for precise sky sub. - e.g. Precission photometry of extended features, intergalactic light in clusters. Spacial strategies Spacio-temporal strategies

  10. Processing and archiving • Raw data • Observed images (VISTA?) • Ancillary information • Calibration results • Calibration files time stamped • Reduced images • Single observation • Coadded images • Software • Methods (pipelines) for processing calibration (depends on how data was obtained) • Configuration files • Source lists – catalogues • Extracted source information (how to extract depends on what the user wants to do: e.g. barycenters vs PSF fitting) • Associated among different data objects Modified from Valentijn 2003

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