When you use 憧憬 as an admiration to someone it's more like a secret love to someone who's superior to you. e.g. 我憧憬着我的师兄。 You can also use 憧憬to express the expectation to something just like "盼望" . e.g 我憧憬着那一刻的到来equals to 我盼望着那一刻的到来。In this case, 憧憬 creates a feeling that breezes . 憧憬 is not used quite often in the speaking.

她在热切的盼望那一天的到来。 女人们往往喜欢憧憬完美的爱情。 盼望， expet something to happen; 憧憬，dream of an ideal state.

憧憬的对象可以是一件事或一个人，而盼望的对象只能是一件事。

Actually the two terms refer to the same thing . However 憧憬is more often used in written Chinese, especially in literary works. 盼望is more used in daily verbal communication. We often say 盼望 or 期盼 something blabla...instead of 憧憬 in our daily life. If someone use 憧憬，we will think that the man is well-educated but a little bit pretentious.