## Correction to Exercise 1.3 Answer

On p. 185 of *The Deep-sky Imaging Primer*, the answer to question 1.3 should read:

An exposure of 20 minutes at 40 degrees Celsius would produce 20 min x 60 sec x 1.68 e- per second = ~2014 electrons. Dark current would fill 2014 / 25500 = ~8% of the full well capacity. The brightest capturable level would be 25500 – 2014 = 23486. The noise from the dark current is SQRT(2014) = ~45 electrons. The read noise is given in the problem as 10 electrons, thus maximum theoretical dynamic range is 23486 / (45 + 10) = 428, or 53 dB.

For the same exposure at -15C, following a similar set of calculations, the dynamic range would be 25468 / 15.6 = 1629, or 64 dB.

(Note that we are simplifying our calculation of total noise here by not using the proper summing in quadrature method, as that is covered in the following chapter, but this simplification does not have a meaningful impact on the results.)

My apologies for the error.