Alignment aberrations of the New Solar Telescope

The New Solar Telescope (NST) is an off-axis Gregorian telescope at Big Bear Solar Observatory (BBSO). This paper presents the expected aberrations due to misalignments of the secondary mirror for a general Gregorian telescope using an optical model of the on-axis "parent" telescope version of NST. The sensitivities of linear astigmatism and constant coma found by perturbing the axisymmetric model are presented and shown to match those predicted by the theory. Then we discuss how the actual aberrations are different due to the off-axis nature of the NST. Finally, we discuss the effect of the misalignments on the pointing of the telescope.

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