"Impossible!" Luna growled as her hoofstamp echoed through the vast gold-domed cavern of the Royal Observatory. "‘Tis an impossible task, a fool’s errand, and here am I, Princess Fool astride it all. A pox on the entire Astronomers' Guild!" As she sat snarling over a tangle of charts and reports a tiny voice broke the midnight silence behind her.
"Everything okay, Luna?" came the small and trembling words.
Luna's ears perked and she sat bolt upright before snapping her head around. "Twilight Sparkle?" She rose and took a few trotting steps to meet the diminutive unicorn as the barest of grins rose on her muzzle and faded as quickly as it had come. "Yes, all is - ah, indeed, no. I am frustrated, Twilight. Annoyed, in truth."
Twilight shifted on her hooves, the weight of a heavy saddlebag dragging her aside. She glanced out the observatory's open dome, past the great brass telescope that dominated the room and into the star-strewn night. "Still trying to fix the stars?"
Luna nodded as her nostrils flared. "Indeed. Upon my return I found my precious stars scattered 'cross the heavens, my own skies barely familiar. 'Twas but two short years ago, and e'en now the task eludes me." She stalked across the room, Twilight in tow, and settled to her haunches on the observatory's balcony, now open to the evening air. "Verily, I cannot blame my dear sister. She was much occupied with sundry more pressing tasks, and tried her best with unfamiliar stars. With her attentions elsewhere, the state of Equestrian astronomy fell to disrepair. Neither can I blame the Guild, I suppose, for they could not rightly be expected to investigate stars whose movements may change year to year, or night to night, as Celestia's attentions waxed and waned."
"Speaking of which," Twilight muttered as she sat down by Luna and set aside her saddlebag, "where are the Royal astronomers, anyway? The staff said I'd find you here, but on a perfectly clear night like this I expected they'd be fighting over the telescope."
Luna snorted and curled back a lip over grinding teeth. "Gallivanting about Canterlot on account of some holiday or another, it seems." Silence crept over them as Twilight seemed to shrink back a little. Her gaze fell to the floor and with a hoof she traced an idle pattern on the glossy tiles. “I am sorry for my outbursts,” she sighed. “They were not directed at you, I assure you. Many things changed in my absence, Twilight. Much of Equestria now stands unfamiliar to me, even foreign. I thought to find comfort here, at least, among my beloved stars, yet even these seem alien to me.”
She managed a weak smile and turned to Twilight. “Forgive me my grousing, if you will. I am prone to such bouts of melancholy in my old age, or so I am told.”
Twilight gave the larger alicorn a quick nuzzle. “It’s okay, Luna. You may be a Princess but you’re still a pony too. You’re entitled to bad days just like the rest of us. Besides, you’re not old,” she chuckled quietly as she smirked. “You don’t look a day over three thousand.”
Luna raised an eyebrow in mock indignation before grinning widely and giving the young mare a playful nudge with her wing. She shook her head and pointed a hoof at the star-marked saddlebag. "So,” she grinned, “what's this burden you've brought tonight, my Little Spark?"
A soft magenta glow from Twilight's horn opened the saddlebag and lifted from it a heavy tome, thicker than her hoof and plain-bound aside from a pair of stars stamped on its cover. "This is…" she began, her voice mouse-quiet and faltering. "I, um, I brought this for you." She levitated the book toward the alicorn and deposited it feather-gentle at her hooves.
Opening the book in her own indigo magic, Luna sifted through page after page packed with charts, diagrams, and notes in a script both dense and precise. "Star charts?" she asked as she ran a hoof over the reams of data, "and… more, it seems?"
"A chart of stellar drift over the last thousand years," Twilight blurted enthusiastically. She cringed at the too-loud echo in the cavernous Observatory before continuing, now subdued and shaking a little. "I dug up old star charts from the Royal Archives and compared them with observations over the last millennium, cross-referenced with anything I could find: collected letters of past Chief Astronomers, constellations woven into the tapestries lining the Royal Dining Hall, whatever I could get my hooves on. I sorted the list by magnitude and spectral class, starting with the brightest. Using this, you should be able to restore most of your stars to their correct positions relatively quickly." A smile almost dared its way across her face before it was drowned in a warm and growing blush as she looked quickly down and away. "At least, the first eight hundred and fifty or so. That’s as far as I got."
“Remarkable,” Luna said quietly, "and now the impossible seems suddenly less so." She slowly closed the book and eased a caressing hoof across its cover. "Twilight, this book represents hundreds, perhaps thousands of hours' work. All of this you did… just for me?"
Twilight inhaled deeply and bit her lip. Looking up to meet Luna's sparkling, star-filled eyes with her own, she whispered, "Happy Hearts and Hooves Day, Luna."