If you have watched Setokai no Ichizen, or GJ-bu, or Setokai Yakuindomo, then you are well prepared for this anime, which for some reason is not listed as ecchi. The Asstronomy (spelt that way on purpose) club does almost nothing with astronomy. Sure they make vague references to it, and there are hints that they all like it, but more than anything, this anime is a source of puns, parodies, references, and slapstick comedy.
The thought process goes something like this: "Plot? what's that? Like this? OH! you mean like this!" pretty much the first half is just enjoyable fun, and what little plot it does have is actually pretty good, if somewhat shoddily delivered.
Nevertheless! do not let this deter you from watching this anime if you are just hoping for some good laughs. If you are a person who values plot and character development, then try something like Medaka box. Otherwise, enjoy!