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#Photox air free

^ High Energy Astrophysics: Particles, Photons and Their Detection Vol 1, Malcolm S.

"Origin of Sodium and Lithium in the Upper Atmosphere". The Publications of the Astronomical Society of the Pacific. "Sky Variability in the y Band at the LSST Site". "OH Emission Bands in the Spectrum of the Night Sky II". "OH Emission Bands in the Spectrum of the Night Sky I". If we take the example of a V=28 star observed through a normal V band filter ( B = 0.2 μm bandpass, frequency ν ≈ 6 ×10 14 Hz), the number of photons we receive per square centimeter of telescope aperture per second from the source is N s: At visible wavelengths, we need the parameter S 0(V), the power per square centimetre of aperture and per micrometre of wavelength produced by a zeroth-magnitude star, to convert apparent magnitudes into fluxes – S 0(V) = 4.0 ×10 −12 W cm −2 µm −1. In order to calculate the relative intensity of airglow, we need to convert apparent magnitudes into fluxes of photons this clearly depends on the spectrum of the source, but we will ignore that initially. Other chemicals that can create air glow in the atmosphere are hydroxyl (OH), atomic oxygen (O), sodium (Na), and lithium (Li).

#Photox air free

The free atoms are available for this process, because molecules of nitrogen (N 2) and oxygen (O 2) are dissociated by solar energy in the upper reaches of the atmosphere and may encounter each other to form NO. This photon may have any of several different wavelengths characteristic of nitric oxide molecules.

One airglow mechanism is when an atom of nitrogen combines with an atom of oxygen to form a molecule of nitric oxide (NO). Very low down, however, atmospheric extinction reduces the apparent brightness of the airglow. Although airglow emission is fairly uniform across the atmosphere, it appears brightest at about 10° above the observer's horizon, since the lower one looks, the greater the mass of atmosphere one is looking through.

Partly for this reason, space telescopes like Hubble can observe much fainter objects than current ground-based telescopes at visible wavelengths.Īirglow at night may be bright enough for a ground observer to notice and appears generally bluish.

It is not noticeable during the daytime due to the glare and scattering of sunlight.Įven at the best ground-based observatories, airglow limits the photosensitivity of optical telescopes. Comet Lovejoy passing behind Earth's airglow on 22 December 2011, captured from the ISSĪirglow is caused by various processes in the upper atmosphere of Earth, such as the recombination of atoms which were photoionized by the Sun during the day, luminescence caused by cosmic rays striking the upper atmosphere, and chemiluminescence caused mainly by oxygen and nitrogen reacting with hydroxyl free radicals at heights of a few hundred kilometres.