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EULUMDAT is a data file format used for specification of photometric data especially intensity distributions from light sources such as lamps and luminaries. The file extension is .ldt. The format was proposed by Axel Stockmar (Light Consult Inc., Berlin) in 1990. The format is the European equivalent to the IES file format specified in IESNA ...
To enable rapid access of specific stars in the catalogue, WCSTools software numbers each star using its Guide Star region number (0001 to 9537) and a five-digit star number within each region, separated by a decimal point. sty2 lists Tycho-2 stars by number or sky region. imty2 lists the Tycho-2 stars within an IRAF or FITS image using the world coordinate system defined in its header.
It includes positions, parallaxes, and proper motions for about 1.3 billion stars and positions of an additional 300 million stars, red and blue photometric data for about 1.1 billion stars and single colour photometry for an additional 400 million stars, and median radial velocities for about 7 million stars between magnitude 4 and 13.
There are a number of organizations, from professional to amateur, that gather and share photometric data and make it available on-line. Some sites gather the data primarily as a resource for other researchers (ex. AAVSO) and some solicit contributions of data for their own research (ex. CBA): American Association of Variable Star Observers .
It includes positions, parallaxes and proper motions for about 1.3 billion stars and positions of an additional 300 million stars in the magnitude range g = 3–20, [17] red and blue photometric data for about 1.1 billion stars and single colour photometry for an additional 400 million stars, and median radial velocities for about 7 million ...
The photopic includes the CIE 1931 standard (solid), the Judd-Vos 1978 modified data (dashed), and the Sharpe, Stockman, Jagla & Jägle 2005 data (dotted). The horizontal axis is wavelength in nm. Photometry is a branch of optics that deals with measuring light in terms of its perceived brightness to the human eye. [1]
For each photometric system a set of primary standard stars is provided. A commonly adopted standardized photometric system is the Johnson-Morgan or UBV photometric system (1953). At present, there are more than 200 photometric systems. [citation needed] Photometric systems are usually characterized according to the widths of their passbands:
One characteristic feature of the STAR File format is that data names (keys in key–value pairs) start with the underscore. They are separated from data values only by white space, for example: _format "STAR File" _first_published 1991 The format was designed to provide a concise syntax for tabular data. The construct for this is called loop.