what is the difference between 観察 and 観測


According to JDIC, both mean "observation". Judging from the Kanji used, I'm
guessing the difference is 観測 has a nuance of observing something and
measuring some aspect of it or taking data, whereas 観察 is just to observe and
monitor what's happening.




You guess is right. And 観測 can also mean prediction based on the data observed
(e.g. 希望的観測).

Some details can be found is the explanation of the two word:
[観察](http://dictionary.goo.ne.jp/leaf/je2/14519/m0u/%E8%A6%B3%E5%AF%9F/)
[観測](http://dictionary.goo.ne.jp/leaf/je2/14840/m0u/%E8%A6%B3%E6%B8%AC/)

