I found this image in my album and did a repro. I used the 2k version from
http://i1063.photobucket.com/albums/...s_ngc55_2k.jpg
Most important is that it was done with
102 frames of
20 seconds. Total time of 34 minutes. No guinding. This is fantastic. I believe only because I did.
When I hadn't guiding, I worked very hard to get these and others images. I remember. Good polar alignment and manual correction after each ten frames. And much diplomatic conversation with DSS to accept stack the images with misalignment !
note: it seems that the light pollution here, today, will not permit this capture as it was done.