The word constellation does not appear in the series. However a couple quotes mention fixed stars and set of stars, which from the context certainly refer to constellations.
In another quote a specific star has a name, which is Hesius. Again, from the context, it appears this may be the Gorean name for the North Star.
And finally, not including numerous mentions of the sun as a star, I have listed several quotes which speak of the stars in the context of study of the stars, navigation by the stars, telling time by the stars and just enjoying the stars.
Reference to Constellations
I was more pleased on the second day and made camp in a grassy veldt, dotted with the Ka-la-na trees. The night before, I had ridden over fields of grain, silvery yellow beneath me in the light of the three moons. I kept my course by the luminescent dial of my Gor compass, the needle of which pointed always to the Sardar Mountain Range, home of the Priest-Kings. Sometimes I guided my tarn by the stars, the same fixed stars I had seen from another angle above my head in the mountains of New Hampshire.
Tarnsman of Gor    Book 1    Pages 73 - 74
(emphasis mine)
On the other hand, the High Castes, specifically the Warriors, Builders, Scribes, Initiates, and Physicians, were told the truth in such matters, perhaps because it was thought they would eventually determine it for themselves, from observations such as the shadow of their planet on one or another of Gor's three small moons during eclipses, the phenomenon of sighting the tops of distant objects first, and the fact that certain stars could not be seen from certain geographical positions; if the planet had been flat, precisely the same set of stars would have been observable from every position on its surface.
Tarnsman of Gor    Book 1    Page 41
(emphasis mine)
Most mariners, however, believed that the world was spherical, surmising this from a plenitude of considerations, that one first discerns the masts of approaching ships, that Gor's shadow, round, is occasionally cast on a moon, that not all stars are visible at all latitudes, as would be the case if the world were a plane, and so on.
Swordsmen of Gor    Book 29    Pages 436 - 437
Named Star
"We are not on course," said Tyrtaios. "I was to the helm deck. Half blinded by water I saw briefly, clouds apart in the wind, the star of Hesius. It was at the bow. Four times later, too, on different days, the star of Hesius lay before us. Two helmsmen confirmed this."
Mariners of Gor    Book 30    Pages 130 - 131
(emphasis mine)
Study of the Stars
Even in the earliest, preserved records of war, on both Earth and Gor, it is clear that a sophisticated variety of tactics was already in place, and familiar. There are men who study war with same avidity and attention as others study the materials of the earth and the movements of the stars.
Rebels of Gor    Book 33    Pages 354 - 355
Navigation by the Stars
"My name is Clitus," he said. "I am a fisherman. I can guide ships by the stars. I know the net and trident."
Raiders of Gor    Book 6    Page 85
The men of Torvaldsland sometimes guide their vessels by noting the direction of the waves, breaking against the prow, these correlated with prevailing winds. Sometimes they use the shadows of the gunwales, failing across the thwarts, judging their angles. The sun, too, of course, is used, and, at night, the stars give them suitable compass, even in the open sea.
Marauders of Gor    Book 9    Page 56
There remain, of course, the stars and the winds. Winds are extremely important in direction finding to the red hunter, for at certain seasons they prevail in different directions. Indeed, even in the darkness, the total darkness of an overcast sky in the arctic night, when the winds do not blow, he may often find his way simply by feeling with his mittened hands the alignment of ice crystals on slopes and blocks, which are a residue of the earlier passage of such winds. This is not to say that red hunters cannot become lost. They can. On the other hand an experienced trekker usually has a good idea of his whereabouts. The lay of the land, the winds, the stars, help him with directions, as well as, of course, his own keenly developed sense of orientation, probably selected for in the harsh environment.
Beasts of Gor    Book 12    Page 321
I went back over various things in my mind, the Crooked Tarn, the camp of the Cosians, the trenches, the approach to the wall, my captivity, my escape, the fighting at Ar's Station, the escape from the piers. How complex and desperate had become the world. I felt so small, like a particle adrift on a vast sea, beneath a vast sky, a particle taken here and there, at the mercy of the tides, the currents, the winds, not understanding. But there were compasses and landmarks, as palpable to me as the stars by which I might navigate on Thassa, as solid and undoubted as the great brick structure of the pharos of Port Cos itself. There were the codes, and honor, and steel.
Renegades of Gor    Book 23    Pages 414 - 415
"There are no paths here, no trails," he said.
"None," said I, "which appear on your maps."
"It is a labyrinth," he said, wearily.
"There are the sun and stars, the winds, the flow of the current," I said.
Vagabonds of Gor    Book 24    Page 280
Our course, as I determined from the stars, would continue to take us south of Cos, and north of Tyros. Beyond these island ubarates would be some small, farther islands. It was not clear what might lie beyond those tiny islands.
Swordsmen of Gor    Book 29    Page 595
"But I was alone," she said, "a woman, ill-clad, half crippled, and hungry, unfamiliar with the stars, without guidance, only vaguely aware of where Brundisium might be, or how far away she might be."
Mariners of Gor    Book 30    Page 61
As I suppose I have made clear, I am not by caste of the Mariners. It is one thing to draw an oar, and do one thing or another about a ship, even to be of its fighting complement, and quite another to read the weather, and water, and the stars, to plot courses, to keep a steady helm in a hard sea, to manage lines and rigging, and such.
Mariners of Gor    Book 30    Pages 189 - 190
"Did Pausanias seem to you a skilled navigator, one who might read charts, lay out courses, determine positions by the stars?"
Conspirators of Gor    Book 31    Page 429
I did know that a small unevenness in one's pace, a tiny difference in the stride of one foot as opposed to the other, common in almost anyone, save perhaps those trained in a measured stride, such as warriors, might result in one's eventually describing a vast circle, but I did not think I had covered so many Pasangs as to make that plausible. Too, what of the time of day, and the sun? And certain stars? Could one not gather one's directions from such things? How incomprehensible it all was.
Smugglers of Gor    Book 32    Page 430
Telling Time by the Stars
Although it was late, according to the chamber chronometer, fixed in the lid of one of the chests, I prepared to leave the room. Unfortunately there was no natural light in the room and so one could not judge the time by the sun or the stars and moons of Gor. I missed them. Since I had awakened, the energy bulbs had continued to burn at a constant and undiminished rate.
Priest-Kings of Gor    Book 3    Page 48
It had served as a clock. Factors such as impatience can occasionally distort one's subjective estimations of the length of various temporal intervals. These confusions and distortions, of course, are eliminated, at least to a large extent, by having recourse to various stages in some presumably continuous, objective process. Is this not the sort of thing which is involved in the ringed candles, in the tiny stream of water in the clepsydra, in the falling sand in the Ahn glass, in the alternation of day and night, and in the calendar of the stars? I stirred up the fire again, so that I might better see what I was doing. By now Cuwignaka and Hci should be in place.
Blood Brothers of Gor    Book 18    Pages 386 - 387
Chronometers exist on Gor, but they are rare and valuable. Marcus and I did not have any, of intent, at the time, among our belongings. They would not have seemed to fit in well with our guise as auxiliary guardsmen. In many cities, of course, including Ar, time tends to be kept publicly. Official clocks are adjusted, of course, according to the announcements of scribes, in virtue of various astronomical measurements, having to do with the movements of the sun and stars. The calendar, and adjustments in it, are also the results of their researches, promulgated by civil authorities. The average Gorean has a variety of simple devices at his disposal for making the passage of time. Typical among them are marked, or calibrated, candles, sundials, sand glasses, clepsydras and oil clocks.
Magicians of Gor    Book 25    Page 358
Enjoying the Stars
The night came with infinite slowness, but at last the blinding sun was gone and I welcomed the chill, windy darkness. The water lapped against the side of the frame, the stars sparkled above in frosty detachment. Once, to my horror, a scaled body crested under the frame, its glistening hide rubbing my body as it snapped its tail and suddenly darted beneath the water. It apparently was not carnivorous. Oddly enough, I cried out to the stars in joy, still clinging to life, unwilling to lament the fact that my miseries must now be prolonged.
Tarnsman of Gor    Book 1    Pages 139 - 140
For some reason Parp now seemed visibly uneasy. The sky above the dome was now gray and darkening. The Gorean night above, often black and beautiful with stars, now seemed to be approaching with swift stealth.
Priest-Kings of Gor    Book 3    Page 31
About two hundred yards above the camp, toward the Sardar, whose crags could be seen looming in the background against the black, star-shattered night was a strange figure, outlined against one of the white, rushing moons of Gor.
Priest-Kings of Gor    Book 3    Page 310
We looked about, at the cylinders and lights and bridges. It was a fresh, cool summer evening. The stars over the city were clear and bright, the coursing moons white with splendor against the black space of the Gorean night.
Assassin of Gor    Book 5    Page 172
Beyond the fire, in the distance, like an irregular margin, a torn, soft, dark edge hiding the bright stars of Gor, I could see the lofty, still blackness of the borders of the northern forests. Far off, I heard the scream of a hunting sleen. I shivered.
Captive of Gor    Book 7    Page 113
After some hundred yards I came to the edge of a clearing. It was some twenty-five to thirty yards in diameter, ringed by the lofty trunks of Tur trees. The floor of the clearing was lovely grass, thick and some inches in height, soft, and beautiful. I looked up. Bright in the dark, star-strewn Gorean sky, large, dominating, seemingly close enough to touch, loomed the three moons of Gor.
Captive of Gor    Book 7    Page 131
It was a hot night. The stars were very bright in the black Gorean sky. The three moons were beautiful. The men lay on their blankets in the sand, under the awnings stretched from the Tesephone.
Hunters of Gor    Book 8    Page 100
I lay in the center of a clearing. I could see lofty Tur trees surrounding the clearing. We were deep in the forest, somewhere within one of the stands of the mighty Tur trees. I could see them, on all sides, at the edges of the clearing, rising beautifully a hundred, two hundred feet toward the blackness of the Gorean night, the brightness of the stars, and then, almost at the top, exploding into a broad canopying of interlaced branches. I could see the stars overhead. But through the leafed branches of the trees I could catch only glimpses of them. There was grass in the clearing. I could feel it beneath my back. I saw, to one side of the clearing, a short, stout slave post, with two rings. No slave was bound to it.
Hunters of Gor    Book 8    Page 127
I looked up, at the narrow apertures in the wall to my right. Through them I could see certain of the stars of Gor, in the tarn-black sky.
Marauders of Gor    Book 9    Page 1
I lay in the arms of Clitus Vitellius, my master, under the bright stars of Gor, under the white moons and the black sky, on the rough wood, in the midst of that great, lonely sea. I heard the water lap at the wreckage on which we lay. He had freed me of the ring, that my hands, under his directives, might pleasure him.
Slave Girl of Gor    Book 11    Page 373
I was looking forward to the return to Port Kar. It is beautiful to fly alone by night over the wide fields, beneath the three moons in the black, star-studded sky. One may then be alone with one's thoughts, and the moons, and the wind. It is beautiful, too, to so fly, with a girl one has desired, bound over one's saddle, tied to the saddle rings, commanded to silence, her white belly arched, exposed to the moons.
Beasts of Gor    Book 12    Page 99
I then lay back on my blankets, on the grass. I put my hands under the back of my head, on the folded saddle blanket beneath my head. The kaiila saddle and the kaiila quirt lay to one side. I looked up at the stars, and the three moons of Gor. It is difficult to convey the majesty of a Gorean night in the Barrens, because of the vastness of the sky and the depth of the blackness, and the contrasting brightness of the stars. The large extents of wilderness on the surface of Gor and the absence of large-scale artificial illuminations, of course, permit starlit nights, almost anywhere, to manifest themselves with a splendor that would be almost breath-taking to one accustomed to the drab, half-gray, polluted, semi-illuminated, dim, nocturnal atmospheres of Earth. In the Barrens, however, and in places such as the Tahari, probably because of the relative levelness of the terrain, horizon to horizon, these effects seem even more accentuated, even more stupendous, more spectacular, more unbelievable and astounding.
Savages of Gor    Book 17    Page 168
Outside the tent I stopped, and lifted my head, and looked up, into the night, to the stars.
They are very bright in the Gorean night.
Many on Earth, I supposed, had never seen stars so.
Swordsmen of Gor    Book 29    Page 428
