these problems almost always boil down to star detection -
problem 1: the subs have very high noise, such as from an uncooled DSLR. the star detector is confused by the hot pixels and detects them as stars.
problem 2: the FL is really long and the stars present in the image are very soft (meaning they do not have strong peaks)
problem 3: the FL is really long and the tracking/guiding is bad, so the stars are soft and not particularly star-like.
the solution to 1 is to experiment with changing the noise scales and hot pixel compensation in the star detection tab of the StarAlignment process
the solution to 2 is to experiment with the peak sensitivity slider in the star detection tab of the SA process
sometimes problem 3 can not be solved and the only solution is to capture better subs. but #2 does sometimes apply.
a good way to figure out what's going on is to use SA in "detected stars" mode, which will generate an image which shows all the things that SA thinks are stars. you can then see if there are very few stars, or if there are a whole bunch of bogus stars.
rob
