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Fig. 8.

image

Analytical (aluminum), measured (including error bars), and fitted instrumental polarization (IP) of the telescope and M4 as a function of telescope altitude angle in the Y-, J-, H-, and Ks-band from the measurements of HD 176425 taken in 2016 before the re-aluminization of M1 and M3. For science observations the telescope altitude angle is restricted to 30° ≤a ≤ 87°.

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