Hello. This is my first time posting here, so bare with me. I am from Denmark and I am at my final year of what corresponds to Senior High School. I am currently working on a project about "optical instruments" in physics (I was told that our A level corresponded to your applied physics level). I'ts the biggest project we do the entire year, so I am a little stressed about it. Anyway, sorry for the introduction. My question is regarding the path of light and the forming of a picture in a dobble lense system. Part of my assignment was to build my own spyglass. So the system in question consist of: One objective lense with a focal lenght of 30 cm and an ocular lense with a focal lengt of 5 cm. Both lenses have the same size. I know that, when looking at an object through the spyglass i have to ajust the objective lense in order to get a sharp image. But it is unclear to me, what exactlay happens with the lights path when i ajust the distance between the objective- and ocular lenses. I mean, in order to get a sharp image of an object at different distances i have to just the spyglass, but why is that? 2. Relevant equations The magnification of the spyglass is given by f1/f2 = 30/5 = 6x times. (Not really sure if any equations is needed for me question) 3. The attempt at a solution Not sure. Maybe it have something to do with the fact that, the longer the object is away to smaller the viewing angle gets. Atlest thats the only connection i can find. I guess, what i am basicly asking is: What exactly happens inside the spyglass when I adjust the lenght between the lenses in order to get a sharp image? Sorry for the long post, i hope you can bare with me. Also i appologize now, if this forum is not intendeed for these sort of questions. Feel free to ask anything, I can provide more information if needed. Thank you for taking your time.