Want to know if the telescope is properly equilibrated to outdoor temperatures? Use the star test. An uncooled scope will have "currents" of hot air coursing through the tube. These often show up as "plumes," one of which is visible in the intra- and extrafocal images in Figure 5a to 5c. Not sure if the plume is due to improper cooldown or some weird optical aberration? Move the scope so the tube's rotation changes (this is easy with an equatorially mounted scope). The plume should not move.
Was this article helpful?