What is correct calculation for Moon's brightness?

[Jurassic Park]

Hello everybody,

I'm sorry for bothering you,but I joined here for one single question and clarification.

I would like to know how can I calculate Moon's brightness and correct calculation of it with result if possible?

I'm terrible in math and calculations and one guy told me result that is impossible,but I don't get how did he got that result?

Here is his calculation:

Intensity 1/int 2= (distance 2)^2/(distance 1)^2. 1lux/int 2=0,001^2/384400^2=147 billion lux per 1m of Moon's surface.

Can you explain me what did he do wrong and what is the real calculation for it as well as final result since this is obviously impossible.

I read that intensity depends a lot because of the phases and it's usually between 0.05-0.1 Lux and that it can reach up to 0.32 Lux during ''Supermoon''

Can you please help me with this since I suck at these kind of calculations and explain me what should I tell him about his calculation that are impossible as well as correct calculation with result?

Thank you very much and have a nice day.

[beecee]

52 minutes ago, Jurassic Park said:

Hello everybody,

I'm sorry for bothering you,but I joined here for one single question and clarification.

I would like to know how can I calculate Moon's brightness and correct calculation of it with result if possible?

I'm terrible in math and calculations and one guy told me result that is impossible,but I don't get how did he got that result?

Here is his calculation:

Intensity 1/int 2= (distance 2)^2/(distance 1)^2. 1lux/int 2=0,001^2/384400^2=147 billion lux per 1m of Moon's surface.

Can you explain me what did he do wrong and what is the real calculation for it as well as final result since this is obviously impossible.

I read that intensity depends a lot because of the phases and it's usually between 0.05-0.1 Lux and that it can reach up to 0.32 Lux during ''Supermoon''

Can you please help me with this since I suck at these kind of calculations and explain me what should I tell him about his calculation that are impossible as well as correct calculation with result?

Thank you very much and have a nice day.

Wouldn't know the mathematics involved but would guess it has something to do with the amount of sunlight falling on the Moon, the angle involving the Sun, and the albedo of the Moon. From memory, the albedo of the Moon is 12, meaning it reflects 12% of the sunlight falling on it. Hope that might help somewhat. 

[Jurassic Park]

56 minutes ago, beecee said:

Wouldn't know the mathematics involved but would guess it has something to do with the amount of sunlight falling on the Moon, the angle involving the Sun, and the albedo of the Moon. From memory, the albedo of the Moon is 12, meaning it reflects 12% of the sunlight falling on it. Hope that might help somewhat. 

Well,to be honest I don't have a clue how did he manage to get that result since it's impossible to be 147 BILLION Lux per 1m of Moon surface as it would be more bright than a Sun(I don't mean that literally of course).

Standard and by ''standard'' I mean when it's full Moon it's only about 0.05-0.1 Lux.

From Earth, the apparent magnitude of the full Moon is only about 1/380,000 that of the Sun.

That guy likes to show off and he keeps talking how he got ''correct'' results with that calculation,but it's more than too obvious he's lying.

He said that he used moonlight brightness (I guess) and inverse square law light intensity and got those ''results'' that shows that Earth's is not cause of eclipse,because if it was,shadows would look much different.

And yes,I know that he's dummy to express myself in nicest way possible,but I don't know how to tell him he's results are wrong since I don't have clue how did he calculated that in the first place.

He keeps repeating ''inverse square law light intensity'' like he's some kind of Newton reincarnation or something and it's really annoying as hell because I can't tell him his wrong since I'm not sure what's the correct calculation for getting how many Lux is 1m of Moon's surface.

I searched online for that calculation and result,but I couldn't find it anywhere.

It's only partially explained on some sites and it's quite complicated to understand it since I'm not familiar with those calculations,not to mention that the explanation is in ''pieces'' and not fully explained on one site so it's practically impossible for me to get it right without doing proper study about it.

 

[beecee]

1 hour ago, Jurassic Park said:

From Earth, the apparent magnitude of the full Moon is only about 1/380,000 that of the Sun.

He said that he used moonlight brightness (I guess) and inverse square law light intensity and got those ''results'' that shows that Earth's is not cause of eclipse,because if it was,shadows would look much different.

Some one will be along to help in time with your maths query. I'm only a rank amateur with a poor grasp of maths, but just a comment on the above. The Sun is approximately 400 times further away then the Moon, and also coincidently 400 times larger in radius than the Moon. The Moon has over the course of time, gradually moved further and further  away from Earth [at present about  2 cm or so every year] We can then deduce that in the past when the Moon was closer, all eclipses [discounting partial eclipses] were just that, total eclipses irrespective of aphelion or perihelion, and in the distant future when it is further away, all "total eclipses" will all be Annular eclipses.  the following shows an Annular eclipse that presently occurs when the Moon is at aphelion. That same eclipse would be total if the Moon had been at perihelion.

 

Edited August 24, 2021 by beecee

[swansont]

17 hours ago, Jurassic Park said:

1lux/int 2=0,001^2/384400^2=147 billion lux per 1m of Moon's surface.

What is that first distance? How is it chosen?

[Solon]

My calculations based on .25 Lux measured from Earth and using the inverse square law resulted in around 12,000 Lux for lunar surface brightness. NASAs theoretical brightness is 5,500 Lux. Unfortunately there are no published, measured values of lunar surface illumination levels over the course of a lunar day. The only measured values I can find are from the Apollo 8 mission when they used  the 2 degree spot meter on the sun lit portion of the far side and recorded between 160 and 320 Lumens. I think that means that the far side is actually quite dark.

Edited November 12, 2021 by Solon
correct previously posted Lumens value