umm ..ermmm .. i'm embarrassed to say it Phil
, i didnt use it astronomically until the warranty was over .. i was still mainly into film for astro work, other than quick twilight snaps, so is my fault to a degree,
here's an example of it, funny but the longer the exposure, the less trouble it is!? in fact you dont even notice it really, but anything up to and around 30 secs is really bad!
here's an example, ive exaggerated it and converted to grayscale to show it clearly