OK, so I'm on the Black Star quest, which I have done before on a previous character.
I've gone to the shrine, talked to Nelacar and my quest log currently is directing me toward Ilinalta's Deep.

Now I know where Ilinalta's Deep is, and I think in the previous playthrough I had already discovered it prior to activating this quest. But right now it isn't showing on my map (no update) and there isn't a quest marker.
My questiosn are these: Is there an in-game way that I'm supposed to know where to go?
Was my map supposed to update or was I supposed to be directed to someone else for information? (the latter is not likely in Skyrim, I know)

Like I said, as a player I already know where it is, but if I didn't, my character would be wandering the map aimlessly hoping to stumble upon it.
For RP, I'm using clairvoyance, but it feels like something has glitched.

If Nelacar mentioned it, it should appear on your map. I think I bribed him for the information, can't recall right now. Hopefully the quest will continue on as it should once you go there though. Good luck.

Do you have the quest activated? The map marker may not show if you don't. (along with the direction arrow)

It's definitely Ilinalta's Deep. Just head on down there, pop in a holler "halloooo" to get things going.

Mine did something similar. Had already explored it, but once I got the quest it wouldn't let me fast travel there. Other than that it worked just fine.

I did have the quest activated so that clairvoyance would work.
After I "discovered" the location, it showed up on the map along with the quest marker.
Cleared fine, the Star was there and quest updated to the next stage. Must have just been a glitch.
Thanks for the help, all.