Possible Duplicate:
When is it necessary to use a hyphen in writing a compound word?
What is correct, deep-sky object or deep sky object? Does common usage trump grammar?
Or, alternatively, if they are both correct, which one should be preferred?
Possible Duplicate:
When is it necessary to use a hyphen in writing a compound word?
What is correct, deep-sky object or deep sky object? Does common usage trump grammar?
Or, alternatively, if they are both correct, which one should be preferred?
Googling around, I find that the non-hyphenated form is considerably more prevalent. But as for grammar, the hyphenated form is more correct, since deep is modifying sky, not object.
Deep-sky object = [Deep sky] [object]
The non-hyphenated form would be correct if both deep and sky were modifying object:
Deep sky object = [Deep] [sky object] or [Sky object which is also deep]
The best clincher on this I could come up with is that Ngrams, which only analyzes books, has no instances of deep sky object; only of deep-sky object:
Granted, there are not many hits, but it's still a lot compared with zero.
If I had to choose, I would choose the hyphenated form.
The inconclusive discussion is a Wikipedia article about a game by that name where the article was apparently highjacked by astronomers - what would they know?
Both spellings are used in the article. But there doesn't seem to be confusion.
The answer to your question might depend on who you're communicating with: astronomers or grammarians.
But I suspect both parties would say "It doesn't matter"