As the Pixiv caption goes, 'Oyasume, (Goodnight) Satorin'
BTW, anyone have any ideas as to a better translation program than Babelfish? My hirugana is crappy, but even I could make out the proper caption; Babelfish got that all wrong, saying it was "Phosphorous and gold".
You could try WWWJDIC or Google's language translation page, but honestly, when it comes to translating names or nicknames in hiragana, you just have to know what it looks like to begin with. Machine translators will never have the necessary breadth of context recognition to do the job you want here.
As another alternative, if you're using Firefox and know katakana and hiragana, there's the Rikaichan add-on. Like Moonspeaker said though, knowing the name or nickname and probably some basic knowledge of Japanese sentence structure can help.