A word on 2024 known problems (and solutions)

• The optical diffusion problem that was detected in Sept 2024 (mostly affecting the He D3 observations) has been identified and corrected (November 2024).
• The data acquisition issue in polarimetric modes was tracked down to a bad sync between the analyzer rotation and the camera exposure. This has been solved at the cost of slowing down the acquisition loop (roughly a factor 2 slower). This issue has been affecting all the September 2024 runs.

1. MTR2 in spectroscopy mode In this mode we propose up to 4 (old) EMCCD Andor iXon camera (512×512) and up to 2 (new) Andor Zyla (2kx2k) cameras. Both 6 cameras can be setup and used at the same time (with their respective specs), in accordance with the SP2 output physical limitations.
2. MTR2 in spectropolarimetry mode: In this mode, 3 cameras (hence 3 wavelengths) at most are available, from the above list. It is possible to combine polarimetric and non-polarimetric cameras. Our polarimetric analysis scheme is based on a full-Stokes analyzer located at the F1 prime focus. For any solar polarization state to measure, the output of the analyzer is made of dual superimposed complementary linear polarizations. Thanks to our “polarization friendly” new optical scheme, this output travels through the telescope and arrives unperturbed on the spectrograph cameras. Just in front of the camera, a Wollaston splitter separates the beam into complementary Stokes components to form the spectral focal plane. Regarding the available analysis software:
   • A Stokes map quick-look is now available.
   • Thanks to V. Bommier, a basic magnetic field inversion software package (running locally in IDL) is available.
3. Broadband imaging context camera: this is running concurrently with the spectrograph. Current setup is for 656 nm (red), but this can be changed optionally to G-band or other.
4. Adaptive optics is available and tested over sunspots and granulation with good results oversignificantly long periods of time (seeing dependent).
   • A slowed-down (100Hz) version of the same system can be used to stabilize Mercury.
   • At the moment it is not possible to use the AO over the solar limb (or for neighboring prominences).

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