The most common and most likely answer to this crossword clue is the 7 letter word PALOMAR
P
A
L
O
M
A
R
More clues leading to the result PALOMAR
Buddy explains!

The straight part
We know that "Observatory" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case observatory = palomar.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.