Canon darks...

[roundycat]

You will not notice much difference between a master dark made from 20-30 individual darks compared to fifty. It is still the actual signal from the target you want to keep the random noise down. Thermal pixels are easily dealt with and can be more or less completely eradicated with Median or Sigma based rejection combined with dithering. Then you don't need any darks at all but you must subtract Bias if not using Dark subtraction.

Software should not be placing any numbers requirement on the number of darks. The reasoning behind using an odd number probably has its source in mis-understood schoolboy maths. Some think you need an odd number to calculate the Median - not true.

See here Astrophotography for info on noise.

Dennis