The stars are very important to Tyson.
To quote from a thread with flight-of-the-thieving-magpie:
For Tyson and his Synesthesia, star charts were the same as any other maps, though he’d needed to learn how the map changed orientation throughout the year. [x]
The Delaney family manor was outside of the city, but still close enough to Cambridge to be affected by its light pollution. It had been a mixed bag when looking up at the night sky. When looking towards the city, some stars were still visible but even the highest ones were dulled. When looking out towards the hills, however, Tyson had a clearer view. “Myb-brother, Jethro, used to sneak me outside at night t-to go swimming in the creak.” …“It was amazing, h-how much clearer the stars were back t-there. I kept ignoring his attempts to teach m-me how to swim to watch the stars instead. H-He found a book about constellations for me when we g-got back home. Of course, as it was father’s l-library Jethro took it from, it was almost t-too old to read from, but…” Tyson let out a soft chuckle. “I fell in love with t-the tales. It was a collection of Roman and G-Greek fables about the stars. Finally there w-were maps that other people cared about like I d-did. Only they weren’t just lines on a page, but f-flickering above instead. Almost tangible.” [x]
“Whatever tales they hold, however, s-stars are denoted by maps and maps will always b-be mathematics. Pure and miles from s-simple.” The corners of his mouth twitched into a fond smile, his gaze slipping from Jim to the space between them, as he continued, “Mathematics permeates everything. Where it n-not for mathematics those stories would mean nothing more to me than fairy tales do. Maths is the life blood of the universe, the secret to every glimmer of light above and to the void between. It is as beautiful as the stars themselves. A hidden code, a hidden language, throughout everything in existence.” [x]
To Tyson, the stars are beautiful maps that he can share with other people. That people can appreciate on, if not the same, a similar level to Tyson. It’s something Tyson can share with the Moriarty Mirrors and know that they understand each other perfectly, can see that childlike wonder in their eyes and know - whatever his doubts - he made the right choice to become their Pup.
He loves every legend, story, & fable about the stars. He loves the connection they give him to people, be it on an aesthetic, literary, mathematical, scientific, or spiritual level. Even though Tyson doesn’t believe in Astrology, he is always respectful of other people’s beliefs and any love of the stars is appreciated in Tyson’s eyes.
The stars have always been a constant comfort in his life. Untainted by the abuse of his father, Jethro running away from home, the lows and highs of his time in the army, The Colonel’s abuse, his time on the run, or his time with the Moriarty Mirrors. The stars are always there, sometimes in a different place or invisible to the naked eye but always there.
In Tyson’s Synesthesia, the stars are always bright, positive colours. By and large, constellations will all be seen in the same colour, but there are a few exceptions, when a star within a constellation is important on its own: golden Sirius in red-violet Canis Major and bright green Arcturus in pastel pink Boötes, for example.