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Refractive error print that page


A refractive error , or refraction error , is an error in the focusing of light by the eye and a frequent reason for reduced visual acuity . Contents 1 Classification 2 Diagnosis 3 Management 4 Epidemiology 5 References 6 See also [ edit ] Classification An

Navigation print that page


Hemisphere by sighting the North Star Polaris with a sextant and sight reduction tables to take out error for height of eye and atmospheric refraction . Generally, the height of Polaris in degrees of arc above the horizon is the latitude of the observer. [ edit ] Longitude Further information

Eyeglass prescription print that page


Background 3 Lens power 4 Spherical lenses and spherical correction 5 Amount of refractive error and degree of blur 6 Cylindrical lenses and cylindrical correction 7 Axis 8 Spherical equivalent refraction (SER) 9 Distant vision and near vision 10 Optical axis and visual axis

Scientific method print that page


Although procedures vary from one field of inquiry to another, identifiable features distinguish scientific inquiry from other methods of obtaining knowledge. Scientific researchers propose hypotheses as explanations of phenomena, and design experimental studies to test these hypotheses via

Coastal management print that page


In some jurisdictions the terms sea defense and coastal protection are used to mean, respectively, defense against flooding and erosion. The term coastal defence is the more traditional term, but coastal management has become more popular as the field has expanded to include techniques

Corrective lens print that page


indices 5.2 Disadvantages of increased indices 6 Optical quality 6.1 Abbe number 6.2 Power error (-D corrections for myopia) 6.3 Lens induced oblique astigmatism (+D corrections for presbyopia) 6.4 Minimizing power error and lens induced astigmatism 6.5 Self refraction

Intercept method print that page


as it is within, say, 50 NM of the actual position (or even 100 NM would not introduce too much error ). Compute the altitude Hc and azimuth Zn with which an observer situated at that assumed position would observe the body. If the actual observed altitude Ho is smaller than the computed

Astigmatism print that page

optical axis. This may be by design (as in the case of a cylindrical lens), or due to manufacturing error in the surfaces of the components or misalignment of the components. In this case, astigmatism is observed even for rays from on-axis object points. This form of astigmatism is extremely

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Lunar distance (navigation) print that page


earth who can see the same two bodies will observe the same angle (after correcting for parallax error ). The navigator then consults a prepared table of lunar distances and the times at which they will occur. [ 1 ] [ 6 ] By comparing the corrected lunar distance with the tabulated values

MISTRAM print that page


A "classic" ranging system used since the 1960s uses radar to time a radio signal's travel to a target (in this case, the rocket) and back. This technique is accurate to approximately 1%. The accuracy of this technique is limited by the need to create a sharp "pulse" of radio so that the start