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"Earthshine blog"

A blog about a system to determine terrestrial albedo by earthshine observations. Feasible thanks to sheer determination.

Brighter-Fatter effect

From flux to AlbedoPosted by Peter Thejll Feb 09, 2014 01:33PM
In an interesting paper by Antilogus, et al subtle effects of electron interactions inside the CCD material itself are discussed, which could be a tool for understanding and perhaps quantifying CCD nonlinearity.

We have tested our own Andor BU987 CCD camera for these effects and see them.

Plots of row- or column-neighbour means vs correlations. Top row: first panel: full set of values of means vs column-correlations - we note the strong non-linearities that set in at about 50.000, and some outliers.
Top row: second panel: for just the range of mean values below the onset of non-linearity a robust regression is performed (red line).
Bottom row: same as top row but now for row-correlations.
We note the general correspondence to results in the 'brighter-fatter' paper: rows are more strongly correlated with their neighbours than are columns - the ratio of slopes is about 2.0.

Can this be used quantitatively to correct for non-linearity in our CCD? The camera linearity was already tested for linearity while in Lund. See Figure 8 in the report.

  • Comments(3)

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Posted by Augustin May 09, 2014 10:37AM

I found you with a 'brighter-fatter' search on Google.



Posted by Peter Thejll May 07, 2014 05:51PM

Hi! Thanks for your comment! We will discuss it and get back to you. How did you find our blog entry?



Posted by augustin May 07, 2014 05:42PM

"Can this be used quantitatively to correct for non-linearity in our CCD?"

I see figure 8 of your Report that you talk about PTC non linearity and not non-linearity of CCD sensitivity.

Yes indeed, pixels spatial correlation is the reason why you see PTC non linearity.
Be careful about what you assume to be a gain measurement. Your method is highly biased.