Crystal Lake Observatory Tracks Pulsating Stars

Crystal Lake Observatory, located in Cambridge, New Zealand, is an astronomy research station, equipped with impressive telescope and camera equipment to capture distant astronomical data. They are conducting a photometric study of RRab-type variable stars. This is a subtype of RR Lyrae stars that pulsate in brightness with remarkable regularity. By precisely measuring their light output over time, the observatory produces detailed light curves that reveal patterns in the stars’ pulsation periods and amplitudes. These stars typically brighten and dim in cycles lasting less than a day, and their highly predictable behavior makes them valuable tools in astrophysics—particularly for studying stellar evolution and measuring cosmic distances. Long-term monitoring helps detect subtle changes in these cycles, contributing to our understanding of aging stars and the dynamics of our galaxy. 

An observatory’s line of sight to its target stars can become partially or fully obstructed, which in turn affects brightness measurements. One common obstruction is cloud cover at night, which can lower brightness measurements by varying amounts depending on the clouds. While cloud cover may seem hard to quantify or even identify, especially at night, clouds increase long-wave radiation readings on earth’s surface below. Long-wave radiation (in combination with temperature and humidity) data can be used to filter out obstructions that would decrease the light measured from the RRab stars. To account for such variable cloud conditions, this observatory uses an Apogee SL-510-SS Upward-Looking Pyrgeometer sensor to measure long-wave radiation. An Automatic Partial Cloud Amount Detection Algorithm processes the data provided by this sensor alongside temperature and humidity data to quantify cloud cover during hours of darkness.