[Aavso-photometry] Cosmic Rays

[Michael Newberry]

You say cosmic rays at "half a dozen electrons". That's a little tight. What 
is your noise level?

Michael

----- Original Message ----- 
From: "Ben Davies" <ben at davies.net>
To: <aavso-photometry at mira.aavso.org>
Sent: Friday, January 27, 2006 5:39 PM
Subject: Re: [Aavso-photometry] Cosmic Rays


> Hi Michael,
>
> I measure cosmic ray levels from as low as half a dozen electrons all the 
> way up to saturation.  Sometimes the hits are big and bright and fade to 
> low levels.  Sometimes they are very low level from start to finish - no 
> more than a couple hundred electrons in the brightest pixel.
>
> You would prefer not to have any of these falling inside the outer 
> annulus, so I guess 'nearby' is as good a term as any.
>
> Ben
>
>>
>>
>> Can you please explain exactly what your goal is? Are you trying to avoid 
>> measuring a star in an image if there is a cosmic ray nearby?
>>
>> Michael Newberry
>>
>> ----- Original Message ----- From: "Ben Davies" <ben at davies.net>
>> To: <aavso-photometry at mira.aavso.org>
>> Sent: Friday, January 27, 2006 2:07 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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