Galileo's Camera

In the last post, I wrote about what is collimation and what sort of an effect a non-collimated telescope has on imaging. Taking it from there, let's see what are the equipment we can use in collimating a telescope. No-Tools: Firstly let's ask the question whether we can collimate a telescope without almost any tool. It is possible for someone with real good patience and a reasonable eye-sight could collimate a telescope that is not seriously misaligned just by star-light (point at a star, keep adjusting up until the slightly out of focus image stops being an ellipse and becomes a disc). However using a collimation cap makes the job much more easier. It is not necessary to collimate the telescope during the night when using this method. It is possible to perform daytime collimation by center-spotting your primary mirror. What is center-spotting? It simply means marking the exact center of the primary mirror. Some of the telescopes come with the center marked from the factor...

For any reflecting telescope, collimation of the optics is one of the most important and regular tasks. Collimation simply refers to aligning the primary mirror and the secondary mirror along with the eye-piece. However, the job it self is not that simple. If a telescope is not collimated, the image it creates would not be in the same plane as the eye or the projection plane (in case of a camera/ccd/projector is used). This could lead to various ring patterns, distortion of the image to appear when viewed. This means that even when you have focused the image properly (or brought the viewing plane up to the focal point), the image is still not clear/smeared. Fortunately, this it self provides an easy way of identifying whether or not a telescope is properly aligned. Ray diagram of an uncollimated Newtonian - Red line depicts the plane where the image is created. The green line depicts the viewing plane. To try to understand what happens in an uncollimated telescope, let's ...