Improper. -'a' means the sentence is a question to be answered with a yes or a no. nuq means the sentence is a question to be answered with a noun or pronoun in place of the nuq. They are incompatible.
Saying qaS'a' nuq? would be kind of like saying What's up, right? in English.
"What's up?" and "What's going on?" would be said in the same situations and with the same meaning. The grammar is slightly different since "What's up?" is a simple present and "What's going on?" is a present progressive. And though these tense differences in English are not exactly the same as the aspect difference in Klingon, there is quite a bit of overlap and we ask that you match the "-ing" ending in English with the -taH ending in Klingon. So we would be more likely to accept "What's going on?" as a translation for qaStaH nuq?