What's with the "HDC" designators?
Occasionally you'll see stars from PTI referred to as "HDCxxxxxx" (eg. HDC189733) rather than the right name (eg. HD189733). This traces its roots back to a obscure software bug at PTI that didn't allow target identifiers to start with anything other than 3 alphabetic characters - so the "C" was added to "HD". Sorry.

Other 3-letter prefixes for PTI targets:
IRC - IRC+xxxxxx targets
IRM - IRC-xxxxxx targets
HIP - Hipparcos targets