Argelander's grade estimation method

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The Argelander step estimation method is a method for determining the brightness of stars with the naked eye. This method was developed by the German astronomer Friedrich Wilhelm August Argelander (1799–1875). Basic features go back to Wilhelm Herschel . In contrast to Pickering's fracture method , it appears to be more complicated to use. The level that is expected here is initially a relatively subjective measure. This subjectivity is largely eliminated in further processing.

method

Several stars (no variables) are selected whose brightnesses are close to the star to be compared (V). It doesn’t matter whether it is brighter or weaker. The brightest star is designated with a, the second brightest with b ... A level assessment is then made according to the following criteria and the stars are arranged from left to right in a decreasing order of brightness

Level 0: Both stars appear equally bright, or sometimes one is perceived as brighter than the other (V 0 a).

Level 1: At first glance, both stars appear equally bright. If you compare them carefully for a long time, it turns out that the star (here: a) appears brighter every now and then. In the notation (here: a 1 V), the lighter of the two is always put in front.

Level 2: For longer comparisons, the star (here: a) is undoubtedly and always brighter than the comparison star, even if only to a small extent (a 2 V).

Level 3: If the difference in brightness in favor of the star (here: a) is noticeable fairly quickly, a 3 V is written.

Level 4: If there is an even more striking difference in favor of the star (here: a), then we write a 4 V (if the comparison star were significantly brighter than the star, then we write V 4 a).

This procedure takes place with all selected stars. The level value is determined in a comparison matrix, with the help of which the brightness of the comparison star can be calculated.

example

An estimate based on the steps described above results

a 2 V
b 1 V
V 1 c
V 3 d

Now a matrix is ​​created

a - b b - c c - d
 1 2 2 level value

The brightest star is set a = 0 levels and the brightness of the stars is taken from a catalog.

 Star level value brightness

a 0 4.55
b 1 4.63
c 3 5.00
d 5 5.11

The difference in brightness d - a is 5.11 - 4.55 = 0.56 The mean level value is 0.56: 5 = 0.112

From this it follows

to star a 4,774
to star b 4.742
to star c 4,776
to star d 4.774

with an average brightness value of the comparison star of around 4.77.

This method is particularly effective in determining the brightness of variables and novae or supernovae .

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