|
Chris nothing much is gained by increasing the number of exposures
it's all about signal to noise ratio more signal is collected by taking longer subs
There are different sources of noise in digital images. Dark current noise
increases with time, and is the same for one image or a stack of equal exposure.
Readout noise occurs with every image however, and for short exposures is a significant part of the total noise. The advantage of long exposures is that the readout noise becomes insignificant.
There is an advantage to using shorter exposures in order to
minimize tracking problems however most imagers find a compromise position, using guiding with subexposure times ranging from between 5 and 30 minutes, and then stacking as many as required, usually for total exposures of one to several hours.
With a digital camera, your options are much more limited. In most cases, you will simply collect a great many images at the longest possible exposure. Noise will be large compared to what you would have with a cooled, long exposure camera, but that doesn't mean you can't get quite nice results.
cheers
|