[Aavso-photometry] average vs. median

[Ben Davies]

What exactly are cosmic rays anyway?   I put a thin lead sheet over my 
ccd and they seem to zip right through it.  So they must not be alpha 
particles.  And I would think that x and gamma rays are too far blueward 
to be detected. What's left?

And whatever they are, are they always going to leave bright, obvious 
tracks, or are many going to go unnoticed on visual inspection?

Ben Davies