Stability of the telescope tube since the start of nominal operations. Data are aggregated to one point per visit. The values of the four front and rear quadrants are shown. Top: Arithmetic mean (AM) and median (MD). Bottom: Peak-to-peak variation (P2P) and standard deviation (SD). Since thermal stability requirements on the telescope tube were not stringent (5 K), an accuracy of less than 1 K was deemed satisfactory, and the thermistors have not undergone extensive calibration. Jumps in the curves can be seen when power cycling the instrument as voltage levels change.