On Thursday, 5 March 2015 16:31:08 UTC, Metman2012 wrote:
On 05/03/2015 16:22, Tudor Hughes wrote:
On Thursday, 5 March 2015 12:50:01 UTC, Metman2012 wrote:

The magnitude (i.e proportion of the sun's diameter covered) in Bracknell was 0.970 and the proportion of the sun's area covered 0.969. The two figures are rarely the same, the area proportion being less than than the diameter proportion except near totality when the moon is "large".
I strongly disagree with Will's assertion that an obscuration of 90% is barely detectable. I have seen an eclipse (25 Feb 1971) where the obscuration was only 58% yet the sun, in a clear sky, looked just a little weak and slightly "wrong". I'd say less than 50% is probably undetectable without instruments. This is, of course, because of the eye's enormous dynamic range. Full sun compared to full moon is at least half a million (19 camera stops) but you can still read a newspaper.

Tudor Hughes, Warlingham, Surrey.

Thanks Tudor, I'll change my notes to say 97%. May I ask where you found
this?

It's from a program I wrote myself in BASIC and runs on an Acorn Archimedes. I do this sort of thing, mathematical astronomy. I seem to one of the very few amateur astronomers who is not scared of numbers. If you want data for any eclipse, just ask.
I can get the position of the moon and sun accurate to 1-2 km over a period of over 2000 years by comparison with published data on ancient eclipses. The only uncertainty is in the rotation of the earth which is slowing down.

Tudor Hughes, Warlingham, Surrey.