Septentrional

Meaning: Cotgrave:

Northerlie, of or in the North.

Usefulness: 1 (OK, it might not be that useful, but it's a ten dollar word you can bandy about, and it sounds good: septentrional. I'm proposing it as the antonym for Antipodean; anyone north of the equator is a septentrionan.)

Logofascination: 1 (From the Latin for seven plough-oxen, referring to Ursa Major or Minor - the OED has Major, so I'm going with that.  Either way, it's because those stars can help you find North... if you're in the Northern hemisphere, of course. The Southern Cross is the southern equivalent; it can be used to find south if you're ever below the equator.)

In the wild:  Digging about in Trove, (don't blame me if you get lost in there) I found a rather lovely piece from 1911 on the British Navy coming to Cromarty, and how much Sir Thomas would've appreciated it. As if his writing on the subject were not enough to mark him one of the logofascinated, our anonymous Englishman's casual use of a word like septentrional in his second-last paragraph is a dead giveaway.

Trepidation

Meaning: Cotgrave: Trembling, terrour, feare.

Usefulness: 1 (As a friend pointed out recently, particularly useful as a description of how one feels while awaiting the arrival of a hangover; dread and trembling indeed.)

Logofascination: 1 (From shaking or trembling in PIE to alarmed or scared in Latin, through various shifts through both meanings in English, and with a diversion into the astronomical, the history of this word oscillates between the shaking and the scared. I sense it has swung toward scared of late, and possibly out into foreboding, but given its history, this may not last.)

Heliacal

Meaning: rising and setting with the sun - when applied to stars, those that rise just before or set just after the sun, since if they rise or set at exactly the same time you wouldn't be able to see the star.

Usefulness: 1 (Stars move through this cycle, which has allowed people to do various clever and useful things by tracking them.)

Logofascination: 2 (Heliacal means relating to the sun, and as etymonline points out, a heliacal year can also be a canicular year, thanks to our friend Sirius, the dog star.)

Acronycal

Meaning: happening at sunset; an astronomical term referring to stars which rise at sunset.

Usefulness: 1 (Mainly in poetic senses, although it could also be used to describe one's martini, depending on how early or late sunset is.)

Logofascination: 1 (Besides my being mildly infatuated with star-words at the moment, it's worth pointing out that the slightly odd-looking spelling is due to its etymological parentage. It's not from chronos, as in time, but from acro- and nycti-, or night-rising. Its opposite - rising at dawn - is cosmical.)

Quadrantids

Meaning: it's a meteor shower which occurs in January, and is named after an obsolete constellation (do constellations get severance pay?), Quadrans Muralis. The Quadrantids now live in the Boötes constellation, but have kept their original name. Boötids certainly doesn't have the same ring to it.

Usefulness: 3 (you wouldn't get to say it much; useful if around astronomers, in need of a particularly difficult trivia question, or looking for a name for an alien species in your latest SF work)

Logofascination: 1 (it just sounds lovely)