Re: Everett and Howell Paper

[Chris Albertson <chrisalbertson90278@yahoo.com>]

I think the E&H's longer focal length helps.  Even if
both groups have three pixel wide PSFs, TASS's three
pixels see just over 500 square arcseconds of sky while
E&G's three pixels see less then 2 square arcseconds of
sky.  Even if the sky is as dark as 20mag/square arcsecond
this has to make a difference


>      - is it hardware, specifically full-well capacity or
>           effective PSF size?  Again, I think "no".
>           Both groups use CCD chips with relatively shallow
>           full well capacities.  The Everett and Howell paper
>           implies that they ignored pixels with more than 70,000
>           electrons (though they don't state it directly).
>           The Mark IV has a similar gain (3 electrons/DN),
>           and its full-well capacity is about 80,000 electrons.
> 
>           We put all the light from a star into a relatively
>           sharp PSF, with a Full-Width-at-Half-Max of about 3 pixels;
>           one of the reasons is that our pixels are so big, about 7.5
>           arcsec on a side.  E&H use a much smaller pixel scale
>           (0.43 arcsec/pixel), but focus the light into a FWHM
>           of 1.4 arcsec, which works out to about 3 pixels.


   Chris Albertson             
   Redondo Beach, California
   home:   310-376-1029   chrisalbertson90278@yahoo.com
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   office: 310-336-5189   Christopher.J.Albertson@aero.org