In some sources, amplitude and semi-amplitude are used interchangeably. Grant Foster's light curve analysis book provides context (p 130).
In any case, I've verified that the y-axis in VStar's amplitude vs period/frequency plot represents semi-amplitude. You can verify this for yourself by running DCDFT against a signal with a sem-amplitude of 1 such as the one attached.
The question was prompted by light curves and analysis of an unusual star which varied between ~7.1 and 7.5 for a few days, then between ~7.5 and 7.9 for another few days. True range therefore about 0.8 mag. DC DFT in VStar shows an amplitude of about 0.35.
Couldn't check using a true sinusoid - away from home without a computer.
Hi Roy
It's semi-amplitude.
The y-axis title should be revised accordingly for clarity. I've created a ticket for this:
https://sourceforge.net/p/vstar/bugs-and-features/685/
In some sources, amplitude and semi-amplitude are used interchangeably. Grant Foster's light curve analysis book provides context (p 130).
In any case, I've verified that the y-axis in VStar's amplitude vs period/frequency plot represents semi-amplitude. You can verify this for yourself by running DCDFT against a signal with a sem-amplitude of 1 such as the one attached.
David
Thanks David,
I thought so, but wanted to check.
The question was prompted by light curves and analysis of an unusual star which varied between ~7.1 and 7.5 for a few days, then between ~7.5 and 7.9 for another few days. True range therefore about 0.8 mag. DC DFT in VStar shows an amplitude of about 0.35.
Couldn't check using a true sinusoid - away from home without a computer.
Cheers,
Roy
Hi Roy
I've made the change to the code and user manual so it will be in the next release.
David
Thanks David
Best wishes for the New Year.
Roy
Best wishes to you for the New Year too Roy.
David
I am wondering why 'DC DFT amplitude - or is it semi amplitude?' still displays intermittently as an active topic when it is not.
Roy