Table of Contents
The SONG spectrograph
The spectrographs among all sites are effectively the same, and have been designed by Paolo Spano.
Optical Design
The basic optical design of the SONG spectrograph is pictured here. The light from the telescope gets collimated on an off-axis parabolic (OAP) mirror (CM1) before reaching the diffraction grating. After recollimation at the second OAP (CM2) it gets further dispersed by a prism before forming an image that falls on the detector. The overall design is extremely compact.
Echelle grating
The grating is manufactured by MKS | Newport Richardson. The item number is 53A33ZD06-174E, with serial # MR263-2-3-1. Some of the commercial information can be found online here.
Grooves/mm: 31.6
Coating: AgMF2
Curvature: plano
Blaze angle: 76 deg.
Ruled area: 96 mm
Blank size: 100x340x50 mm
The efficiency curves from Richardson Gratings testing are here.
The Zygot measurements are here.
Detector
We have chosen to use the QHY600 Pro detector with the liquid cooling option.