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Looking at the Sky
Published in José Guillermo Sánchez León, ® Beyond Mathematics, 2017
The apparent magnitude gives how bright an astronomical object appears to an observer on regardless of its intrinsic brightness (http://scienceworld.wolfram.com/astronomy/ApparentMagnitude.html).
Entanglement-enabled interferometry using telescopic arrays
Published in Journal of Modern Optics, 2020
Siddhartha Santra, Brian T. Kirby, Vladimir S. Malinovsky, Michael Brodsky
With telescopes of larger aperture the flux of photons is higher. This would require correspondingly higher entanglement generation rates to utilize the larger number of photons received per unit time. With currently available technology the quantum-enhanced interferometric scheme is best suited for measurements of weak astronomical sources if large aperture telescopes are available. For example, if telescopes with diameter 1 m are used then sources with 100 times lesser photon flux on earth than Vega would require the same entanglement generation rate of . In terms of the apparent magnitude system used in astronomy (apparent magnitude of an object in astronomy is defined as where is the flux of photons from the object on earth in the spectral band around x and is the flux on earth from Vega in the same band. Thus weaker sources have a higher apparent magnitude), currently the quantum-enhanced scheme is best suited for the study of weak sources of apparent magnitude 5 or higher for telescopes of diameter 1 m.
Observability and sensitivity analysis of lightcurve measurement models for use in space situational awareness
Published in Inverse Problems in Science and Engineering, 2019
To calculate the apparent magnitude of light received from the object, the fraction of visible sunlight impinging on the object is calculated in combination with the total BRDF. This is a result of sunlight reflecting from the object's facets in the direction of the line-of-sight to the observer. The power per square meter affecting the object caused by the portion of visible light striking the facets is . The fraction of sunlight affecting the body that is then reflected can be calculated using Equation (2), where is the position vector of the observer and is the area of the facet. The dot product accounts for the visibility of the reflection towards the observer. If the angle between the observer's direction and the surface normal or the angle between the Sun direction and the surface normal is greater than π, then there is no light reflected in the direction of the observer and will be zero [9]. The apparent magnitude of the Sun is . Thus the apparent magnitude of the object after accounting for all the facets is obtained as where is the number of facets and for the case of a cuboid, .
Isolating incident and reflected wave spectra in the presence of current
Published in Coastal Engineering Journal, 2018
Samuel Draycott, Jeffrey Steynor, Thomas Davey, David M Ingram
The modified reflection method presented in Section 2, along with the unmodified equivalent, have been applied to the simulated time series with estimates of incident and reflected spectra shown in Figures 3 and 4. As expected due to being an idealized simulation, when incorporating the wavelength change, the incident and reflected wave components are found precisely (Figure 3). When these wavelength changes are omitted (Figure 4), there are significant errors in the apparent magnitude of the spectra, along with a “spiky” discrepancy. This discrepancy is a function of the coarray separations relative to the wavelength discrepancy at each frequency. It is also apparent that whichever wave system (incident or reflected) opposes the current will appear incorrectly amplified if the wavelength alteration is omitted. This clearly demonstrates the requirement to use the modified dispersion relation in order to obtain accurate results.