|
Just to clarify my last post....
To be correct, fixed pattern noise is the wrong term. I simply used it as it best described what the noise "looks" like.
In Alex's case we are getting shot noise, (which reduces with exposure time) on top of less than perfect calibration data. When you stack images that are drifting in a uniform direction the end result is a herringbone pattern in the stacked data.
This pattern disappears with nil drift plus applying a random dither to the guide star tracking.
|