Exploring disparities in design methodologies between astronomical instruments used in space and those employed on the ground reveals intricate nuances and distinct operational principles. Design for applications is always based on stiffness, while the ground applications will be based on strength. This study delves into the contrasting design methodologies employed in the development of astronomical instruments for space and ground-based observations. Astronomical research heavily relies on specialized instruments to observe and collect data from celestial bodies. However, the unique environmental conditions and operational requirements of space and ground observatories necessitate distinct design considerations. In this investigation, we analyze the key differentiators between these design approaches. Space-based instruments, launched into the harsh vacuum and radiation of space, demand robustness, compactness, and energy efficiency. In contrast, ground-based instruments face challenges related to atmospheric interference and require adaptive optics systems for compensation. We explore case studies of prominent space and ground-based observatories, such as the recently launched VELC on board ADITYA L1 and the 90 inch (at VBO) Telescope, to highlight specific design strategies and innovations. Additionally, this talk discusses the impact of advancements in technology and materials on the evolution of these instruments. By shedding light on the nuanced design disparities between space and ground astronomical instruments, this study contributes to a deeper understanding of the specialized engineering required for the advancement of observational astronomy. Such insights are crucial for guiding future developments in this field and optimizing the capabilities of these instruments.