Dumb question

[Chris Lloyd <cl@astro1.bnsc.rl.ac.uk>]

Forgive me if this is a dumb question, but I suppose the aperture used for
the photometry is large enough to encompass the whole image at the centre
and edges of the field. I was prompted to ask by the comments in a recent
posting about the shape of the images at the edge of the field. Having
looked at TN70 I can see where the figure of 7 pixels comes from but
depending on how the aperture is centred it may be possible to lose the
faint extremities. I wondered if any experiments had been done to compare
photometry across the field using different aperture sizes. If not then
perhaps DS24 is where to do it.

Apologies for any dumbness...

Chris