(meteorobs) Cosmic rays on CCDs

Gural, Peter S. PETER.S.GURAL at saic.com
Tue Aug 23 12:35:29 EDT 2011


Cosmic rays can generate various length streaks across today's sensitive
CCDs. The length varies according to the incident angle of the cosmic
ray relative to the normal of the focal plane. That is if the cosmic ray
hit perpendicular to the CCD face, then the pixels lit up would be a
short segment or even a single pixel. While if the cosmic ray came in at
a shallow grazing angle to the focal plane, then a long linear streak
would be seen. They tend to be jagged, the same way that a line drawn on
a pixilated grid makes a stair-step sort of appearance (loosely
speaking). They also only tend to last a single frame, thus making it
possible to distinguish between meteors by the latter's persistent
movement across several frames. Cosmic ray tracks also do NOT show the
point spread function (smearing of light across several pixels due to
the optics) that stars or meteors produce.

A few years ago I ran a detection algorithm on a cover closed, dark
enshrouded PC164 camera, and found about 2 cosmic rays per night.
Today's Watec 902H2 Ultimate is more sensitive and may have more hits
per night but I have not tested this.

 

Cheers... Pete Gural

 

 

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