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Paper: MegaPipe 2.0: 10000 Square Degrees of CFHT MegaCam Imaging
Volume: 523, Astronomical Data Analysis Software and Systems XXVIII
Page: 649
Authors: Gwyn, S. D.
Abstract: MegaPipe, the MegaCam data processing pipeline at the CADC, has been upgraded to version 2.0 and has processed over 10000 square degrees of the sky. MegaPipe has been operating since 2008. It was originally intended to increase the usage of archival MegaCam data by calibrating and stacking the images as they became public. That focus expanded to include processing data from the CFHT Large Programs such as the NGVS, OSSOS, VESTIGE and CFIS, as well as PI data. MegaPipe 2.0 represents several improvements. The advent of GAIA means that the astrometric calibration is considerably more accurate. The public release of Pan-STARRS allows photometric calibration of images even if they were taken under non-photometric conditions, by using the PS1 stars as in-field standards. Together this means that almost every MegaCam image can be astrometrically/photometrically calibrated to sufficient accuracy to allow stacking (30 mas and 0.01 magnitudes respectively). MegaPipe 2.0 also introduces an improvement to the stacking method. MegaPipe previously only stacked images that were centred on more or less the same part of the sky, which limited the number of images that could be stacked. MegaPipe 2.0 instead stacks on a grid of 10000x10000 pixel tiles, each half a degree square, evenly covering the whole sky. The result is that twice as much sky area can be stacked. There are now over 10000 square degrees of imaging in both the ugriz filters as well as the narrow band filters. The data is available for download at:
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