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Fig. 9.


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 217343 taken in 2018 after the re-aluminization of M1 and M3. For science observations the telescope altitude angle is restricted to 30° ≤a ≤ 87°.

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