Whenever one under takes light painting under the Milky Way, a variety of things must be taken under consideration. Timing is everything, and you have to wear a variety of hats, including those of a weather man and astronomer, and not just a photographer. The Milky Way migrates across the sky through out the year, and over the course of the evening. Then you have to worry about what the moon is doing, as it can ruin the entire shot if its high in the sky and near its brightest. You also have to keep in mind how the subject of the shot, in this case, Balanced Rock in Arches National Park, is oriented in relation to the Milky Way, and any man-made light pollution sources. In relation to the latter, Moab is still pretty small, so Arches is one of the best places to take shots like these, not withstanding the wonderful geologic landmarks it and southern Utah are world famous for.
National Park Service – Arches NP