Pixel Value and Exposure

[Mr Giovanni Di Giovanni]

Good morning everyone
I would like to use my nikonD3000 camera, (very simple camera) for photometry of the sky at sunset and sunrise. I have performed several preliminary tests to establish some properties of the ccd sensor. An annoying and unexpected problem has arisen: The pixel values of the same subject (e.g. white sheet of paper illuminated evenly by constant light) are not proportional to the shutter speed. In some well-known manual (which I will not quote) on ccd astronomy, proportionality between PV and exposure is mentioned. Attached is a graph obtained. The system’s response is similar to a process fundamentally akin to charging a capacitor. I do not intend to purchase a new camera. For photometric purposes what to do? Thank you.

Attachments:

1. 

   graficoPVEsposizione.bmp
   

2. 

   graficoPVEsposizione-1.bmp
   

[Author]

Posts