"John Ladasky" wrote in message
om...

... When these planets
pass in front of their parent stars, the light loss is pretty small,
peaking at around 2%. So you need to make really accurate
measurements of the intensity. Twinkling and other atmospheric
variations are a problem. The pixels on a CCD are not perfectly
uniform, either. How sharp is your focus? Is the light of your star
falling exactly on one pixel, or on several?

For this work, wouldn't it be better to use something
with a larger active area, a photodiode for example?
The focus shouldn't matter as long as all the light
falls on the detector.

I guess twinkling is more difficult since it can draw
in light from a wider effective aperture so the post-
processing would need to take care of this.

What if the voltage that
you supply to the CCD varies a bit from time to time? Then,
successive images of the star would not be directly comparable. Have
you saturated any pixels? Is your CCD response linear? Is your
analog to digital conversion 8-bit or 12-bit?

Are the rates low enough to do photon counting from
a photodiode? Counting events should be fairly
resistant to bias voltage variation and the linearity
and quantisation problems would be reduced unless
your bandwidth was low enough to get multiple photons
seen as individual events at a significant rate.

... Then you would need to do
a fair amount of math to tease out the variations as a function of
time.

Presumably the prime part of any processing would be
a Fourier transform and a major problem is the limited
and irregular observing times.

What am I missing?

George