Dome systems denominated as “Clamshells” have been extensively used for the deployment of small telescopes. They are characterized by small price and fast deployment time. Recently, several efforts have been spent for the design of larger clamshell domes, with the aim of adapting them to observatories hosting 4m class telescopes. This poses new design challenges, since astronomical observatories of that size are characterized by the need of several subsystems at the service of the telescope, whose characteristics barely fit with the design of existing clamshells. In this paper we present the development of newly designed clamshell dome systems, whose characteristics make them completely compliant to the requirements of high-end, conventional dome system products, in terms of sealing, HVAC conditioning, wind-protection, and service cranes. We also present and discuss the results of the manufacturing and integration of the first two systems realized by EIE following such design approach, and we present possible applications to large telescopes.
Clamshells are perfect small-sized domes able to satisfy many specific needs of possible telescope array applications. After in-depth studies conducted by the EIE Research and Development (R&D) department, this paper provides an overview of how it is possible to design scaling Clamshells of different diameters capable of guaranteeing excellent protection of the equipment inside, excellent resistance to wind and possible earthquakes, flexibility in the possibility of implementing additional accessories, and easy maintenance. In particular, the paper will deal with Clamshell’s structure, motion system, access, lightning protection system, heating, ventilation and air conditioning system, corrosion protection system, and deicing system.
Proper thermal behavior of a telescope mainly means three things: 1) avoid thermal-induced deflections, 2) avoid high solid-to-air temperature differences that cause seeing, and 3) maintain the temperature of the electronics and of the optical instruments within their operative range. To evaluate the ability of the telescope to fulfil the thermal aims in the design phase, at least two types of thermal models are used: finite element models, and dynamic block models. EIE developed a complete procedure to integrate the two types of thermal models, based on the concept of thermal modal analysis.
High vibrations levels are detrimental to telescope pointing performance. Unfortunately, the true (final) vibration level on the telescope structure can be measured only when the machine is commissioned, i.e. much after the design phase is over. In this context, to reduce engineering risk, it can be useful to assess telescope vibrations very early - also in the preliminary design phase - in order, if needed, to adopt suitable countermeasures (e.g.: vibration damping, structure stiffening, or vibration isolation). This is particularly important in giant telescopes, since their natural frequencies are typically low enough to fall next to many vibration sources (wind, pumps, bogies, electric fans, vortex shedding). EIE developed an integrated procedure to assess the vibration level at the telescope hosted units - mirrors and instruments. The procedure: (i) identifies the relevant vibration sources, (ii) evaluates the vibration level for each source at the generation point, (iii) transfers the vibration from the generation point to the hosted units, and (iv) combines statistically the vibration sources to get the final vibration level. This paper presents EIE integrated procedure for the vibration assessment, and it discusses the most relevant vibration sources to be taken into account in giant telescopes.
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