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IRAF Tools for ESO imaging survey data

Version : 4
Author(s) : Richard Hook in conjunction with the EIS team
License : ESO
Website :

Disk space required for installation is 1.63 Mb


This version is somewhat specific to the ESO Imaging Survey (EIS) and
the following public surveys and may not be suitable for other data.

When coadding EIS images suitable scripts are usually prepared using
the "parapredriz" task and "drizzle" is not run directly. It is recommended
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 the
pixels. This makes the process faster with a minimal loss of quality.

Drizzling takes the input pixel grid and associates with each pixel a square
region (a drop) whose size can vary between that of the original input
pixel (pixfrac = 1.) down to a point (pixfrac=0). With uniform, equal
weight images pixfrac=1 is equivalent to "shift-and-add".
If the shifts and pixfrac are arranged so only one input pixel is drizzled
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, a value
of pixfrac=1.0 is used.


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