Hello! New kid on the block! I've got a question. If one were to build a really large reflecting telescope with say a square km primary mirror. What size would the secondary mirror have to be and what should the distance between them be? Also a related question. I was just reading that to aquire some of the lastest quasar images the Hubble had to stay aimed at a specific target for 13 hrs. Why don't thermal variations caused by the relative solar position during that long an exposure defocus the image? Thanx for your time!
Both depend on the f-ratio of the primary. The optics are actively kept at the same temperature. - Warren
F-ratio. is that the curvature of the mirror? If so is there an optimal curvature? Does that curvature relate to any other factors, ie, freq of light used for imaging/
I'd advise you to learn basic geometric optics before embarking on the construction of a square-kilometer mirror. The f-ratio of a mirror is the ratio of its focal length to its aperture. The lower the f-ratio, the more strongly curved the mirror. - Warren
