9.3 Computing Exposure Times
To derive the exposure time to achieve a given signal-to-noise ratio, or to derive the signal-to-noise ratio in a given exposure time, there are four principal ingredients:
- Expected counts C from your source over some area.
- The area (in pixels) over which those counts are received (Npix).
- Sky background (Bsky) in counts/pixel/second.
- The detector background, or dark, (Bdet) in counts/second/pixel and the read noise (R) in counts of the CCD.
- Section 9.4 provides the information for determining the sky-plus-detector background.
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