How can I calculate the visual magnitude of a star with only its flux data?

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Discussion Overview

The discussion revolves around calculating the visual magnitude of a star using only its flux data. Participants explore the relationship between flux and magnitude, referencing equations and standard values necessary for the calculation.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant inquires if it is valid to calculate the visual magnitude using the formula ma = -2.5log10(Fa) given only the flux Fa.
  • Another participant notes that the reference values for the "b" indexed quantities must be chosen based on the scale being used, suggesting that standard reference values are necessary.
  • A subsequent reply points out that the relevant values for "m" can be found in a specific table, although there is confusion about their availability.
  • Another participant emphasizes that reference values should not be sourced from Wikipedia and suggests consulting a library or textbook for accurate information.

Areas of Agreement / Disagreement

Participants express differing views on the validity of using the proposed formula without a reference magnitude and the appropriateness of sourcing reference values from Wikipedia. The discussion remains unresolved regarding the best approach to obtain the necessary reference values.

Contextual Notes

There is uncertainty regarding the selection of reference values and the implications of using different scales for the calculation. Participants highlight the need for proper sources to ensure accuracy in the calculations.

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How to calculate the visual magnitude of a star having only the flux of such star?
The equation involves 2 magnitudes and 2 fluxes, corresponding to 2 objects a and b:

ma-mb= -2.5log10\left( \frac{F_a}{F_b}\right)

but I just have Fa and I have to obtain ma.

Is it valid to take ma=-2.5log10 Fa?
 
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Ok, but in that table the values for "m" don't appear, only the fluxes :-s
 
Ok, but in that table the values for "m" don't appear
... yes they do: right at the top of the 4th and 5th columns where it says "m=0". But you can use any reference values that make sense in terms of your coursework.
Specifically: you should not get your reference-values off wikipedia. You must have access to a library or a textbook or something like that?
In a pinch - go to wikipedias primary source.
 

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