# The Naked Scientists Forum

### Author Topic: Exactly how much brighter is the eclipsed Sun than a full moon?  (Read 3752 times)

#### spinfun

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##### Exactly how much brighter is the eclipsed Sun than a full moon?
« on: 02/06/2008 18:39:18 »
Hugh Hunt asked the Naked Scientists:

The sun is ~ Mag -26.8, the full moon is ~ -12.7 .

My question is "what is the magnitude of the eclipsed sun at totality" or in other words "exactly how much brighter is the eclipsed sun than a full moon"?

What do you think?

#### DoctorBeaver

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##### Exactly how much brighter is the eclipsed Sun than a full moon?
« Reply #1 on: 02/06/2008 19:18:47 »
Technically speaking, we cannot see a totally eclipsed sun. What we see is the moon passing across the sun. As the moon appears exactly the same size as the face of the sun, this has the effect of blacking out the disc of the sun itself enabling us to see the corona, which we cannot see under normal conditions.

Being pedantic (who, me?), the sun is still as bright as ever, but we just cannot see it.

However, I think you want to know how much light from the sun reahes us at totality compared to that from a full moon. Erm... dunno

#### syhprum

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##### Exactly how much brighter is the eclipsed Sun than a full moon?
« Reply #2 on: 02/06/2008 19:24:38 »
Apart from the light that comes the corona (not much) there is quite a bit scattered from clouds outside the path of totality, I have only seen one Solar eclipse 1999 and it did not get very dark.

#### DoctorBeaver

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##### Exactly how much brighter is the eclipsed Sun than a full moon?
« Reply #3 on: 02/06/2008 19:29:26 »
Wasn't that a partial? Or were you abroad?

#### syhprum

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##### Exactly how much brighter is the eclipsed Sun than a full moon?
« Reply #4 on: 02/06/2008 22:35:17 »
After waiting over 60 years for it I made sure and took me off to Karlsruhe it was cloudy with drizzle but it cleared just in time and I had an excellent view.

#### turnipsock

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##### Exactly how much brighter is the eclipsed Sun than a full moon?
« Reply #5 on: 03/06/2008 00:57:14 »
The eclipsed sun has a mag of -14.1

#### lyner

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##### Exactly how much brighter is the eclipsed Sun than a full moon?
« Reply #6 on: 03/06/2008 09:36:43 »
I think, being pedantic?, that the magnitude during a total eclipse will depend upon the actual distance of the Moon at the time; its does vary a bit, I believe.
But, from the above info, the difference is about minus one and a half; only just noticeable if you look upon a relative magnitude of one as being a visibly small difference. (Original basis of magnitude, I believe)

#### syhprum

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##### Exactly how much brighter is the eclipsed Sun than a full moon?
« Reply #7 on: 03/06/2008 10:12:13 »
I was probably in error believing that back scatter from clouds was a significant factor.
Apparently width of the shadow track is in the region 200/250 km so unless one was close to the edge there would be none.
What is the source of the light then ? is it from the corona ? or is it from light reflected from the Earth onto the Moon?
It is often noted that cloud or mist clears at the last moment and ones disappointment turns to joy, does the shadow have some small effect on the weather or is this just wistful thinking
« Last Edit: 03/06/2008 10:17:04 by syhprum »

#### lyner

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##### Exactly how much brighter is the eclipsed Sun than a full moon?
« Reply #8 on: 03/06/2008 10:20:05 »
You can (often) see the bits of Moon in shadow even without a total Solar eclipse. I always assumed it was Earthlight reflected. We are the next brightest thing around.

#### syhprum

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##### Exactly how much brighter is the eclipsed Sun than a full moon?
« Reply #9 on: 03/06/2008 21:54:19 »
it would be interesting to measure the brightness of the Moons surface as it eclipses the Sun to see to what degree it accounts for the residual light

#### The Naked Scientists Forum

##### Exactly how much brighter is the eclipsed Sun than a full moon?
« Reply #9 on: 03/06/2008 21:54:19 »