Menelvagor or Menelmacar?

[Manwe]

I'm reading The Silmarilion right now an I wander about the Orion stars, in Eä known as Menelmacar, swordman of the sky( or something like that ). However in Lotr somwhere it says Menelvagor. Is it the same, has it changed name or is it just a bad translation?

[Sharkû]

LOTR, appendix E:
"The Quenya combination ht has the sound of cht, as in German echt, acht: e.g. in the name Telumehtar ‘Orion'. [...] Usually called in Sindarin Menelvagor (I, 53), Quenya Menelmacar."