[Aavso-photometry] Cosmic Rays

[Wolfgang Renz]

Hi Ben

If you average/sum combine the differential images, you'll lower
the detectability of the artifacts as they will just appear in a
single image. If you combine 10 images, its just 1/10 of the
difference in the affected original, if you combine 100 images,
its just 1/100.

Using something like a "higest absolute deviant combine"
instead, should lead to much better results. I don't know if
such an algo is implemented anywhere, but it should also
be helpful in finding moving minior planets that are just barely
above the background.

Clear skies
  Wolfgang

-- 
Wolfgang Renz, Karlsruhe, Germany
Rz.BAV = WRe.vsnet = RWG.AAVSO



----- Original Message ----- 
From: "Ben Davies" <ben at davies.net>
To: <aavso-photometry at mira.aavso.org>
Sent: Friday, January 27, 2006 10:07 PM
Subject: Re: [Aavso-photometry] Cosmic Rays


> Here is a method I've come up with to analyze cosmic ray hits in 
> photometric images:
> 
> - Make a median of all images.
> - Subtract this median from each of the images to get a set of images 
> that contain all the artifacts.
> - Average combine (or add, depending)  the artifact set.  Now one image 
> contains the defects and another contains the signal..
> - Blink the averaged image against the median.
> 
> If no artifacts fall on or near the stars you are interested in, the job 
> is done.
> If an artifact does coincide, you just track down the offending image.
> 
> I'm probably just stating the obvious here, but it took me a while to 
> figure it out
> 
> Ben Davies
> http://ben.davies.net/
>  
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