biology coarse adjustment kn diaphragm education eyepiece fine adjustment knob instrument lens medical microscope object holder objective turret ocular lens optic optical research science viewing above aeroplane airplane blue cloud clouds conditions flight formations high light plane shapes skies sky sun textures travel up above variations various cloud formations weather boulder canada craggy distance distant far height jasper landscape mountain natural nature panorama peak range river rock Rockies Rocky Mountains rough summit valley view architecture blocks buildings city cityscape England english Great Britain landmarks line London London Eye railway shard skyscraper thames tower train urban water wheel boat Gherkin monument transport Walkie Talkie London Bridge rush hour tower blocks