[Aavso-photometry] Sources of accuracy and precision in photometric measurements

[Radu Corlan]

> >Arne wrote:
> >
> >The AAVSO has been considering doing some tests.  The problem is that
> >every vendor is sure that their algorithm is correct, and if you
> >don't get the right answer, then (a) you aren't using the latest version
> >of the software, (b) the software was not designed for that specific
> >case (such as trailed asteroids), or (c) you aren't using the
> >software correctly.  These are valid points, of course, but published
> >tests are always going to result in vigorous discussions.
> >
> >The easiest first step is to supply a set of images that everyone can
> >use to test their software.  That is what I am working on right now.
> >Arne

I've had some test images online for a while -- see 

http://astro.corlan.net/gcx/test-images.html

They are specifically designed to test for "instrumental" errors rather 
than be an all-encompassing performance test. By comparing results, one 
can detect even very small errors - for example, using truncation rather 
than rounding to 16 bits will generate an error that is well above 
either the "noise floor" of both the test images themselves and the 
reasonably well written aperture photometry code.

One should be able to get essentially perfect results in the sparse 
field case, and reasonable results in the quite difficult (for aperture 
work) crowded field case. 

Radu



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-- 
Radu Corlan      

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