Preliminary estimate of instrumental polarization effects in the LST-3 Large Solar Telescope

This article presents a polarization calculation for the LST-3 large solar telescope. It describes the interaction of the telescope mirrors and includes a calculation of the transmittance of the telescope’s optical system for incident radiation with various polarization states. It estimates the instrumental polarization, cross-talk, and depolarization at Gregorian focus F2 and after tilted mirror M4 of the telescope. The estimate is made using modeling of an aluminum coating on the mirrors for axial and peripheral image points at reference wavelengths in the 400–2000 nm region. The mean Mueller matrices are found at Gregorian focus F2 and after tilted mirror M4. The polarization distortions at the Gregorian focus are insignificant, but they are substantial after tilted flat mirror M4.