IRAF Tools for ESO imaging survey data
Version : 4
Author(s) : Richard Hook in conjunction with the EIS team
License : ESO
Website : http://iraf.noao.edu
Disk space required for installation is 1.63 Mb
This version is somewhat specific to the ESO Imaging Survey (EIS)
the following public surveys and may not be suitable for other
When coadding EIS images suitable scripts are usually prepared
the "parapredriz" task and "drizzle" is not run directly. It is
that this route be followed.
Note that later versions have been optimised for maximum speed by
using a constant kernel - a square on the output grid, aligned with
pixels. This makes the process faster with a minimal loss of
Drizzling takes the input pixel grid and associates with each pixel
region (a drop) whose size can vary between that of the original
pixel (pixfrac = 1.) down to a point (pixfrac=0). With uniform,
weight images pixfrac=1 is equivalent to "shift-and-add".
If the shifts and pixfrac are arranged so only one input pixel is
onto an output
pixel, the method is equivalent to interlacing. For EIS, where the
data is well-sampled in all but the most exceptionally good seeing,
of pixfrac=1.0 is used.