Abstract Details
| Name: ANNU JACOB Affiliation: Indian institute of astrophysics Conference ID: ASI2016_801 Title : Optics for Prototype Segmented Mirror Telescope Authors and Co-Authors : Padmakar Parihar, Indian institute of Astrophysics Abstract Type : Poster Abstract Category : Instrumentation and Techniques Abstract : To get acquainted with segmented mirror technology and to develop a small telescope which can also be used for a few dedicated sciences, we have initiated a project to develop a prototype segmented mirror telescope (PSMT), of approximately 1.3m physical diameter. Seven identical hexagonal mirror segments with corner to corner length of 500mm, together constitute the primary mirror of the proposed telescope. Various measures have been undertaken to reduce the overall manufacturing cost of the prototype telescope, the important one being the use of spherical optics rather than aspheroid parabola/hyperbola. Initially we explored multiple methods used in the past to correct the spherical aberration introduced by primary mirror. However, finally we decided to correct spherical aberration by making use of ellipsoidal secondary as well as a combination of refractive optics placed near focal plane. PSMT optics has been designed by considering the primary mirror, both as a monolithic and as a segmented. The design was analyzed and it was verified that both approaches give similar image quality. Keeping several design constraints into consideration, telescope optics has been designed, which promises decent image quality for the narrow as well as wide field. The narrow field design offer image quality matching with the local seeing over an arc-minute field of view, without using any correcting optics. Whereas, wide field design require few small optics to correct remaining aberrations and provide good image quality over the field as large as 10 arc-minutes. Sensitivity and tolerance studies were carried out and the effects of manufacturing error on image quality were analyzed. Since primary mirror is made of segments and is driven by actuators, we also explored the possibility of improving off-axis image quality by providing additional tilt to outer mirror segments. In this work, we present our effort to design PSMT optics, which can be an option for the proposed large telescope. |