Since the previous Conceptual Design Study, several analyses has been performed in the field of the Telescope Structure. Those analyses confirm the convenience to use a Gantry mount instead of the pre-selected Rocking-Chair configuration.
The analyses have been performed attending to Dynamic behaviour, as well as the Image motion due to Gravity and Steady State Wind. Image Motion due to Dynamic Wind, including Flexible Body Correction (FBC), has also been carried out.
In all cases, Gantry exhibits a better behaviour in comparison to Rocking-Chair and, if FBC is applied, all requirements are satisfied.
It has also been considered another variant of Gantry mount, i.e., Yoke model, which had not been indeed considered in the previous stage. Although this concept present a weaker performance in comparison to the ones obtained with Gantry configuration, results are just slightly worse and still enough to meet the requirements.
Conceptually, those models are pretty much the same, except the Azimuth Bearing, which could be replace by a conventional Roller-Bearing with a smaller diameter instead of an R-Guides, allowing to dispose the optic transfer and cable wrap on independent compartments but, submitting the platform to bigger efforts. Both alternatives are the ones being considered for future detailed design.
Similarly, an optimization on the upper part of the telescope tube was carried out showing that current design is the best in terms of dynamic behaviour. Only small improvements were obtained for the spider mode, which is not a worrying mode as it doesn’t affect the image motion.
Nasmyth position was also considered, obtaining better results for the case were the platform was placed in the rear side. However, this option implies an increment in the number of mirrors from 4 to 7 or 8, being discarded in comparison to a third option in which the Nasmyth platform is set inside the pier (8 or 9 mirrors).
Detailed design is being performed for Gantry and Yoke mounts, considering Lateral Nasmyth and the possibility of alternating to a possible future inside Nasmyth.