Grouting

grout is a routine specifically designed for tiles coming from VISTA. The program is used to removed the effects of the time variation of the point spread function and any variation in the magnitude zero-point in the 96 images that typically make up a VISTA tile. The user specifies an input catalogue (incatalogue) which should originate from running imcore on a VISTA tile. The provenance information in the header of the catalogue will give a list of the files that were used to create the tile. Even if this catalogue came from a tile that was made with nebulised pawprints, grout only requires access to the pawprint confidence maps and catalogues. If these are not in the current working directory, the you can specify where they are with the command line switch --srcpath. The input catalogue is copied to an output FITS file specified as outcatalogue and the fluxes for the first seven apertures as well as the peak fluxes will be modified by the analysis. All the rest of the information will remain the same. grout will attempt to work out an MJD for each object based on the average MJD for each stack and an weighted mean MJD for each point in the output tile. A  keyword called MJD_DAY will be added to the catalogue table extension. This will be the integer part of the MJD from the first contributing stack. The first unused column in the catalogue (usually called 'Blank##') will be renamed MJDoff. It will contain the number of minutes to be added to MJD_DAY in order to get the MJD of a given object. Hence for the ith object: MJD_i = MJD_DAY + MJDoff_i /1440.0. A map of the distribution of mean MJD offset (in minutes) can be generated if an output filename is specified with the optional switch --mjdmap.