الفهرس | Only 14 pages are availabe for public view |
Abstract Research Objective The aim of this thesis is to develop an automatic focus system for KAO. The automatic focus system nds the best focus by moving the CCD imaging system and measures the image focus level by using a focus measure operator. The focus measure operator is used to determine the focus levels of a sequence of images. The images are acquired at a varying distance between a camera lens and a scene object. The proper focus measure operator is chosen based on a performance comparison of several measures applied to observed astronomical images. 1.4.1 Refracting Telescope A Refracting telescope is an optical telescope that uses a lens as its objective to form an image. It got its name from the fact that its image is formed by bending of light (refraction). A refractor can be a combination of a convex lens and a concave lens or a combination of two convex lenses [4]. One of the main defects of the Refracting telescope is the aberration eects. That is because the light of dierent wavelengths passing through a lens is bent or `refracted’ unequally due to the dierence in refractive index for dierent light wavelengths. Another defect of refracting telescope is the size limitation due to large diculties in constructing large lenses. So, in the most research purposes, the Refracting telescope |