# magnitude system

## magnitude system

[′mag·nə‚tüd ‚sis·təm]
(astronomy)
A system for designating the relative brightness of stars when photography is used; emulsions of different color sensitivities, used with color filters, permit measurements of starlight of different wavelengths with corresponding determination of magnitude at these wavelengths.
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References in periodicals archive ?
Following the development of astronomical thought, the activities relate to topics like the Moon, astronomy measurements, precision astronomy, the magnitude system, spiral nebulae, Hubble's Law, and Kepler's Third Law.
Coincidentally, the catalog of the ancient Greek inventor of the magnitude system, Hipparchus, includes about 850 stars.
The ancient Greek astronomer Hipparchus introduced the magnitude system. He categorized the stars into six magnitudes with the brightest stars assigned to the first magnitude and the faintest to the sixth magnitude.
If we wish to combine measurements with those of other observers, it is often necessary to measure the small differences between our own telescope/CCD/filter system and the standard filter passbands, in order to correct or transform measurements to a standard magnitude system (in this case Johnson V).
The magnitude system began about 2,100 years ago when the Greek astronomer Hipparchus divided stars into brightness classes.
All objects have been placed on a scale relating to their brightness,or luminosity,known as the magnitude system.
Today the magnitude system is based on photometry, and it seems a little confusing that a higher magnitude number means a dimmer object, but that is the custom.
Volume 1, like Burnham's, begins with a roughly 100-page introduction to the astronomy that an amateur really needs to know: the celestial sphere and the sky's motions, the magnitude system, angular measures, and so on, along with lots about the various types of objects to be seen in amateur scopes.
Now let's turn the ancient magnitude system around, so that brighter objects get higher numbers.
Estimating the brightness of stars dates back to the second century BC, when the Greek astronomer Hipparchus devised a magnitude system that's still in use today.
For this, you should change the values for central wavelength (WA in microns on line 40), the peak transmission (TF expressed as a fraction on line 3080), the full-width-half-maximum transmission of the filter (DL in microns on line 3020), the quantum efficiency at the central wavelength (Q given as a fraction on line 60), and the zero of the magnitude system (MO on line 80).
Errors - and there are plenty - range from typos ("Griffith Observatory" is my personal favorite) to errors of fact ("Mariner 4 landed on Mars in 1965") to absurdities (August 24th is the anniversary of Hipparchus's invention of the magnitude system).

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