[pmrid (Peter)]

Here's a bit of a short stack on NGC346 in Ha (6 x 10 minutes only). They have been stacked without any darks of bias frames to see what the raw data is showing. As you can see, there is a serious artifact there. It is composed of a series of bright spots that seem to correspond to the number of subs taken. So the images, whatever they are are marching across the image. Yet the image itself is stable enough. Which I suppose means my guiding was adequate. But if that's so, why are these dots moving?

Peter