An apparatus for determination of an absolute coefficient of thermal expansion in a sample of an ultralow expansion material, comprising: a frame adapted to hold a sample in a fixed position, the frame having a first end and a second end opposite the first end; a first optical sensor supported on the first end of the frame and adapted to detect the position of an end of two opposite ends of a sample held on the frame; and a second optical sensor supported on the second end of the frame and adapted to detect the position of another end of the two opposite ends of the sample held on the frame; and the apparatus being characterized by comprising: a temperature regulator in thermal contact with the frame, the temperature regulator adapted to regulate the temperature of the frame independently of the temperature of the sample held on the frame, wherein the temperature regulator includes an electric heating element in conductive thermal contact with the frame and a temperature sensor for detecting the temperature of the frame, and a controller for operating the electric heating element to regulate the temperature of the frame within a desired temperature range, the temperature regulator comprising a base, wherein the base is provided with the electric heating element and is provided with the temperature sensor, and the frame being disposed directly on top of the base. a frame adapted to hold a sample in a fixed position, the frame having a first end and a second end opposite the first end; a first optical sensor supported on the first end of the frame and adapted to detect the position of an end of two opposite ends of a sample held on the frame; and a second optical sensor supported on the second end of the frame and adapted to detect the position of another end of the two opposite ends of the sample held on the frame; and the apparatus being characterized by comprising: a temperature regulator in thermal contact with the frame, the temperature regulator adapted to regulate the temperature of the frame independently of the temperature of the sample held on the frame, wherein the temperature regulator includes an electric heating element in conductive thermal contact with the frame and a temperature sensor for detecting the temperature of the frame, and a controller for operating the electric heating element to regulate the temperature of the frame within a desired temperature range, the temperature regulator comprising a base, wherein the base is provided with the electric heating element and is provided with the temperature sensor, and the frame being disposed directly on top of the base. a temperature regulator in thermal contact with the frame, the temperature regulator adapted to regulate the temperature of the frame independently of the temperature of the sample held on the frame, wherein the temperature regulator includes an electric heating element in conductive thermal contact with the frame and a temperature sensor for detecting the temperature of the frame, and a controller for operating the electric heating element to regulate the temperature of the frame within a desired temperature range, the temperature regulator comprising a base, wherein the base is provided with the electric heating element and is provided with the temperature sensor, and the frame being disposed directly on top of the base.