I'm back from a long hiatus! Full-steam ahead on the SED Machine project.
The SED Machine camera ensures that the spectrograph is properly focused. Based on the range of temperatures at Palomar, we expect to only use a range of about 300 micron to maintain focus.
Instead of using a dovetail system pushed by a lead-screw we use a pair of flexures from Riverhawk systems. The flexures are preloaded by a pair spring plungers (basically screws with springs to apply a load) against Newport actuator. Today in the lab I measured the final spring constant of the assembled system. The photograph below shows the testing setup: a simple scale gauge pulling on the camera barrel holder.
I love Hooke's law! The applied load as a function of displacement is shown below. The spring constant of the SED Machine camera is determined to be about 1.21 mil / pound force. Note that a mil is defined as inch/1000 or 25.4 microns. Recall that 4 mil is about the same distance as the diameter of a human hair!