Hi Lawrence,
That phrase "large amorphous mass" is very helpful; it makes me reasonably
sure that (as Laurent Zimmermann suggested) you're seeing nebula isophotes.
The fact that you can't right-click on them also suggests that you're
running the "original" Guide 8 software, or at least an older version. I
added the ability to right-click on isophotes shortly after the software
started shipping:
http://www.projectpluto.com/update8b.htm#isophotes
http://www.projectpluto.com/update8b.htm#isophote_contrast
My comment in an earlier post about "if you don't know what something is,
or want to adjust its display, right-click on it", is mostly true. But
there are a heck of a lot of things that weren't adjustable in the original
Guide 8 software. Isophotes were one of them.
-- Bill