This is a scan of an A3 piece (297 x 420 mm) I drew a while back. Open it in a new tab to see the full detail. It too Many Hours (TM). (Around 25 I think?)
Used a variety of technical pens (like Copic multiliners), a refillable technical pen with white ink for the stars (an Aristo MK1 pen), and Prismacolor Premiere pencils for the gemstones.