Assuming that you have a variable star and two (or more) comparison stars. The normal way to calculate the correct magnitude is to check with one of the comparison brighter and one fainter.
It can be showed like this:
- V is the variable star;
- A is the brighter comparison star;
- B is the fainter comparison star;
- x and y are the gradients between the couple (respectively between A and V, and V and B).
Let's see how we can calculate the gradients x and y.
• Zero step: The brighter star (A) and the variable (V) are to be equal for several seconds.
• One step: At the exact moment of observation, if the brighter star (A) and the variable (V) seem to be equal, but after a moment of close examination the brighter star is slightly brighter than the variable, it is considered one step brighter and is recorded as: A(1)V. This means that the A star is one step brighter than the V star (variable).
• Two steps: If A and V appear equal when first observed, but almost instantly it becomes obvious that A is brighter than V, this is recorded as: A(2)V.
• Three steps: If a slight difference in brightness is obvious at the exact moment of observation, then A is three steps brighter than V and is recorded as: A(3)V.
• Four steps: If a distinct difference in brightness is immediately visible, this is considered four steps, recorded as: A(4)V.
• Five steps: A major difference in brightness between A and V is indicated as: A(5)V. You should be careful to choose comparison stars so that less than five steps are needed to make a good comparison. If you exceed five steps, this method rapidly loses accuracy. Good charts will help you select appropriate comparison stars.
The calculation of the derived magnitude is:
V = A + ((x/(x+y))*(B-A))Inside the textarea you can find the relative AAVSO formatted file ready to send. Just copy in a new text file!
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