NavList:

 I always sort of assumed that star to star relationships were basically constant throughout the year. The change in SHA I see comparing pages in the Almanacs suggests to me the relationship to other stars changes slightly based on their sky position relative to each other. 

I knew stars march through the sky approx. 4 minutes earlier each day, but it hadn’t dawned on me they change physical distance relationship to each other significantly (ok, measurably if not a lot).  I had always been led to believe (perhaps in oversimplified navigation explanations),  that stars are so far away the changes in relative position are negligible. I would say almost but not quite, as  there is a yearly positional difference worthy of note. I happen to be lookng at Fomalhaut.

I assume this is because we are hurtling through space on our wet cosmic ball far enough to actually produce the displacment. If so, is that the sole cause or am I missing somehting else? 

MC