Oh well, you are taking a freshman art history class. That makes you an expert. Carry on.
Although The Starry Night was painted during the day in Van Gogh's ground-floor studio, it would be inaccurate to state that the picture was painted from memory. The view has been identified as the one from his bedroom window, facing east,[3][14][15][16] a view which Van Gogh painted variations of[3] no fewer than twenty-one times, including The Starry Night.[17] "Through the iron-barred window," he wrote to his brother, Theo, around 23 May 1889, "I can see an enclosed square of wheat . . . above which, in the morning, I watch the sun rise in all its glory."[3]
Van Gogh depicted the view at different times of day and under various weather conditions, including sunrise, moonrise, sunshine-filled days, overcast days, windy days, and one day with rain. The hospital staff did not allow Van Gogh to paint in his bedroom, but he was able to make sketches in ink or charcoal on paper,[18] and eventually he would base newer variations on previous versions. The pictorial element uniting all of these paintings is the diagonal line coming in from the right depicting the low rolling hills of the Alpilles mountains. In fifteen of the twenty-one versions, cypress trees are visible beyond the far wall enclosing the wheat field. Van Gogh telescoped the view in six of these paintings, most notably in Wheat Field with Cypresses and The Starry Night, bringing the trees closer to the picture plane.[19][20]
One of the first paintings of the view was Mountainous Landscape Behind Saint-Rémy, now in Copenhagen, which Van Gogh identified in a letter to his sister Wil from 16 June 1889 as hanging in his studio to dry.[21] Two days later, he wrote to his brother that he had painted "a starry sky."[22] The Starry Night is the only nocturne painting in the series of views from his bedroom window. In early June Vincent wrote to Theo, "This morning I saw the countryside from my window a long time before sunrise with nothing but the morning star, which looked very big."[23] Two scholars working independently of each other have determined that Venus was indeed visible in Provence in the spring of 1889. So the brightest "star" in the painting, just to the viewer's right of the cypress tree, is actually Venus.[21][24]
The moon is stylized, as astronomical records indicate that the moon was waning gibbous at the time Van Gogh painted the picture.[21] Even if the phase of the moon had been a waning crescent at the time, Van Gogh's moon is not astronomically correct. (For other interpretations of the moon, see below.) The one pictorial element that was definitely not visible from Van Gogh's cell is the village,[25] which is based on a sketch made from a hillside above the village of Saint-Rémy.[26]
Of course he painted things more than once. He stayed there for more than a year. He made studies and sketches constantly.
You don't know what you are talking about.