[Aavso-photometry] average vs. median

[Michael Newberry]

Arne, I'm sure you remember the really big surprise with the 512x320 RCA 
CCD's we used in astronomy in the 80's. I had forgotten about that until 
this thread.

For those of you unfamiliar with those particular chips, in many ways they 
weren't too bad for their era. But there was one really odd feature: the 
cosmic ray count was very high. Either all users happened to be sitting on a 
"hot" mountaintop, or they were hyper sensitive to cosmic rays, or... 
actually neither. It seems they were replicated onto a radioactive 
substrate! Those images were a good testbed for implementing your favorite 
cosmic ray rejection algorithm.

Michael Newberry


----- Original Message ----- 
From: "arne" <arne at aavso.org>
To: "Ben Davies" <ben at davies.net>
Cc: <aavso-photometry at mira.aavso.org>
Sent: Friday, January 20, 2006 1:53 PM
Subject: Re: [Aavso-photometry] average vs. median


> Ben Davies wrote:
>> 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?
>>
> where are you located, Ben?
> Remember, cosmic rays come from all directions, so you would have
> to totally encase the CCD in order to prevent them.  Even common
> things like concrete and UBK7 glass give off radiation that is
> easily detected by CCD cameras.  An interesting email:
> http://www.ctio.noao.edu/pipermail/ccd-world/2001/000474.html
>
> The amount of deposited energy changes too.  Some are point sources
> and bright, some are nearly parallel to the front surface.
>
> Fun things to study if you were a high-energy physicist.  To me,
> cosmic rays are "vermin."
> Arne
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