One of the senior members at the Orchid Board--Mauro--had this to say about growing Aspasia Lunata,
"The trick with this kind of Oncidiinae is to keep the root tips healthy avoiding any kind of injury, especially those caused by the fertilizer salts (assuming you use chemical fertilizers). Also, it is a good idea to adjust the pH of the fertilizing solution to the acidic side, something around 6. I give my Aspasias and Miltonias the same treatment I give my Draculas when the subject is chemical fertilization: I fertilize, wait 20min, half an hour more or less, then I water thoroughly to wash any residual salt away. By doing this you keep the media always free of salts and prevent the root tips from burning (by the chemicals)."
It was news to me so I'm passing it along here.
Here's the link to Orchid Board
Aspasia lunata var. albina - Orchid Board - Most Complete Orchid Forum on the web !