Converting solar eclipse magnitude to percentage?

[ozskywatcher]

Hi,

I am hoping someone can help with the following. I have used the link on NASA Solar Eclipse website for 29 April 2014 http://eclipse.gsfc.nasa.gov/SEgoogle/SEgoogle2001/SE2014Apr29Agoogle.html to Google Maps to find out details for this eclipse for various locations in Australia at time of maximum eclipse.

However, in this information the percentage of the Sun covered at maximum eclipse isn't listed. What is listed instead is the magnitude of the eclipse (ie 0.3). I have tried Googling to see if they are the same thing and haven't found a clear answer. I am hoping that someone on Iceinspace can help me with this question.

I plan to make a pinhole viewer like this one I made for May 2013's eclipse http://nightskyonline.info/?p=4454 Strictly speaking I have already finished it but am needing to add the percentage information before I upload it.

An alternative that people can point me towards would be suggesting software that might give me an answer. I have Sky Safari Pro and the Sky X but neither give me the answer.

Regards,

Paul Floyd.
www.nightskyonline.info

[Merlin66]

The eclipse is usually defined by the amount of the solar diameter covered...ie 90% eclipse = 90% of the solar diameter is covered by the moon.
Why do you need to work out the actual area(s) involved?

[ozskywatcher]

Ken,

I prefer to use percentage because it is something that everyone has been taught in school, and can visualise.

Regards,

Paul Floyd.

[SteveInNZ]

You probably want to use Xavier Jubier's Interactive Google Map (http://xjubier.free.fr/en/site_pages/solar_eclipses/xSE_GoogleMapFull.php?Ecl=+20140429&Acc=2&Umb=1&Lmt=1&Mag=1&Max=1). Click on the place you want to be and it will give you the local circumstances.

Steve.

[ozskywatcher]

Steve,

Thanks. I wasn't aware of that site. I unfortunately now have a slightly different question to ask - which I will post in the Software section of IceinSpace. Xavier's site calculates percentages for maximum BUT only if maximum occurs before the Sun sets. It doesn't do it if maximum occurs after Sunset. Arrg!!

This occurs for various parts of Australia with the 2014 partial solar eclipse. I now need to track down a recommendation for how to work out what percentage of the Sun will be for those locations at Sunset.

You have been a big help as it gives me an answer for some of the locations on my solar eclipse pinhole viewer.

Regards,

Paul Floyd.
www.nightskyonline.info

[EclipseMaestro]

Paul, you have to use the obscuration value, not the magnitude.
The magnitude is the fraction of the Sun’s diameter covered by the Moon at maximum eclipse. However the obscuration is the percentage of the Sun’s disk surface covered at maximum eclipse (displays "???" if the Sun is below the horizon at maximum eclipse).

Both values are usually computed only at maximum eclipse.
To compute the obscuration for areas where the Sun at maximum eclipse is under the horizon would involve the computations of sunrise/sunset time. This is done by my Solar Eclipse Maestro software (http://xjubier.free.fr/en/site_pages/solar_eclipses/Solar_Eclipse_Maestro_Photography_S oftware.html).

Xavier