Re: Minimum spanning circles and Voronoi diagrams

[Tom Droege <tdroege2@earthlink.net>]

Andrew has demonstrated that weak pixels can make big differences in 
photometry.  Just look at that big dip.  But a weak pixel will also "push" 
the position.  So while the error bars that we compute are determined by 
the psf and the pixel sizes and other stuff, the real errors have 
components due to unknown things like a nearby cosmic ray, a local cloud, a 
weak pixel not in our catalog of such, a spot of condensation on the lens, 
etc..

Tom Droege

At 08:43 PM 2/6/02 -0800, you wrote:
>What is the source of astrometric error bars?  Isn't it
>a function of the size of both the PSF and the pixels?