Re: [TASS] Flat fielding

[Herbert R Johnson <hjohnson@PLUTO.NJCC.COM>]

On         Thu, 9 Sep 1999 00:22:17 GMT, Andrew Bennett <andrew.bennett@NS.SYMPATICO.CA> wrote:
*>In TN0019 (960903) Michael Richmond wrote:
*>> I made a flatfield vector for each segment by
*>>calculating the median value of pixels in each
*>>column. I then divided each image by this 1-D
*>>vector. After looking at some of the reduced
*>>images, it appears that I'll need to find a
*>>better way of calculating the flatfield vector;
*>>this method can be screwed up by bright stars and
*>>changing sky brightness.

This is from Richmond's 1996 Tech Note, which is on flat fielding
methods, and his own observing methods. But his observational data is
not in the current Mark III database or in the TenXcat catalog.

*>To which Herb Johnson in TN0057 (Aug 19 1999) added
*>>[The image should be a twilight image of a
*>>high and relatively uniform illumination]

This quote from TN0057 is comments added to a software description of the
"flat" program, said description from the JHU/APL TASS Web page
by Nick Besler at:

http://www.jhuapl.edu/APLastronomy/softwareover.html

...as noted in my TN. My comment was intended to describe a "flat image"
file as different from the data image file. It was not intended
to be a definition of TASS Mark III flat fielding methods, for those you
will have to ask the participants. I do not believe there is a standard
method for flat fielding. I'll modify my Tech Note to be more generic.

The double quote marks are for emphasis, they are not a quotation.

Herb JOhnson

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