By Albert G. Ingalls
Definitive e-book on novice telescope making. comprises plans and thought on a number of kinds. matters coated: Newtonian Telescope reflect Making; Optical checking out; Workshop knowledge; and Observatory constructions.
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Extra info for Amateur Telescope Making
1) Where λ is wavelength, nr the refractive index of the intervening medium and α is the collection semiangle of the lens/aperture and nr sin α is known as the numerical aperture of the lens. 3. Adjacent points in the image would each have a disc associated with them, so one measure of resolution would be how close the points can be brought together, while still being viewed as separate sources. 2 Airy ring, formed by white light travelling through a 1 mm diameter aperture. 3 Intensity distribution across an Airy ring.
These requirements imply that, for most materials to be imaged or analysed at atomic-column resolution, the appropriate thickness will lie in the range up to 50 nm. It would also be helpful if specimens prepared from the bulk could be perfectly flat and parallel-sided with no contamination or surface amorphised layer, while nano-particles could be of regular shape (so that their thickness is calculable from their projected shape and size). Every specimen should resist both ionization damage and displacement damage by the primary beam.
It was realised very early on that the simplest way forward was to acquire images and spectra simultaneously point-by-point, but the electron guns available then were not bright enough to do this in an acceptable time. 9), the source of the electron beam is almost of millimetre dimensions, and must be hugely demagnified if a beam of nanometre dimensions is to be obtained. 10), where the source of the current is of atomic dimensions. But such guns, based on electron tunneling, require upgrading the vacuum system of DEVELOPMENT OF STEM 41 microscopes to ultra-high-vacuum (UHV) standards, technically very difficult and costly.
Amateur Telescope Making by Albert G. Ingalls