Why the DAstronom– thing?
Well, my name is Deno. That’s from the Greek name Κονσταντινος (Konstantinos), which is Anglicized as Konstantinos, Kostas, Denos, or Gus (yes, Gus). The trailing ‘s’ is oftentimes dropped as well, which is how Konstantinos becomes Konstantine, or how Denos becomes Deno.
The Astronom– part is more straightforward. The preceding D is from Deno, and together they make DAstronomer/DAstronomy.