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Lunar Eclipse Tomorrow


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#1 Liam Dale

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Posted 19 February 2008 - 07:54 PM

Hey all,

So there is a lunar eclipse tomorrow night which I was thinking about trying to capture on film, but I've never shot the moon before and am looking for some advice. First of all, I would be shooting on 16mm Kodak 800T and I assume that I would need as long a lens as I can find. I don't have a telescope to shoot through, so would it even be worth it to shoot with, say, a 200mm lens or would the moon just be too small. Also, can you just spot meter the moon and work from there or is there a better method of figuring out the exposure? I would guess that it would need to be timed exposures (thumbs going to be tired from that cable release). I know people tend to just shoot stills and then layer them together into films, but you work with that you've got I guess. Any tips would be appreciated.

Thanks.
Liam
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#2 Jonathan Bowerbank

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Posted 19 February 2008 - 08:02 PM

Also, can you just spot meter the moon and work from there or is there a better method of figuring out the exposure? I would guess that it would need to be timed exposures (thumbs going to be tired from that cable release). I know people tend to just shoot stills and then layer them together into films, but you work with that you've got I guess. Any tips would be appreciated.


Shooting 800 ASA, you should be able to roll at 24 fps, no need for long exposure on this one. On a clear night, shooting 500 ASA, I've metered the moon at f/16. I'm guessing because of the eclipse it'll be a lot lower than that, but it should still be readable.
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#3 Liam Dale

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Posted 19 February 2008 - 08:48 PM

Shooting 800 ASA, you should be able to roll at 24 fps, no need for long exposure on this one. On a clear night, shooting 500 ASA, I've metered the moon at f/16. I'm guessing because of the eclipse it'll be a lot lower than that, but it should still be readable.

Do you just spotmeter the moon? And any ideas about an effective focal length?
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#4 John Sprung

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Posted 19 February 2008 - 09:02 PM

Looking up in the tables, 200mm on a 16 camera gives you a vertical angle of view of 1.8 degrees. The moon's diameter as seen from earth is 0.5 degrees. So, the height of the moon would be between 1/3 and 1/4 of the height of the frame. Can you get a 2x tele extender?

The moon is lit directly by the sun, and the distance difference is insignificant, like about a quarter of a percent. So, you can treat it just like any other object in direct sunlight, except that the actual reflectance of the lunar surface is lower than 18%. I remember overexposing it badly the first time I had to get a shot of the moon. IIRC, at ASA 100 I should have stopped down to about f/16 or f/22. The eclipse just puts a fairly hard cut across the moon, the lit portions stay as bright as ever, they just get smaller. Maybe try bracketing some digital stills before the eclipse starts....



-- J.S.
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#5 Xavier Plaza

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Posted 19 February 2008 - 09:19 PM

I don't know where or when, perhaps in this forum i don't know... But I save this link. I guess this is the time to share, obviously there are a lot of info but value info...

http://facstaff.uww....eadd/index.html

Hope helps



Xavier Plaza
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#6 Jonathan Bowerbank

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Posted 19 February 2008 - 11:15 PM

Do you just spotmeter the moon?


The moon is your subject, what do YOU think?

My advice would be to overexpose by about 2/3's to 1 stop. Your spot meter reads the correct exposure for an 18% grey surface. And as said earlier, its surface is quite a bit lighter than 18%. So stay true to that by overexposing a little to preserve the whiteness of the moon.

Edited by Jonathan Bowerbank, 19 February 2008 - 11:15 PM.

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#7 Vincent Sweeney

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Posted 19 February 2008 - 11:45 PM

Time lapse might be a solution. The whole process will last well over a couple of hours but the action-oriented waxing and waning period will of course be shorter. Maybe a couple frames a second? Mr. Taylor?

I just spotted the high, clear moon here in the east coast US at 24fps, 800asa and I got F32.

Issues to consider: The moon will not suddenly go into eclipse. You may notice some dimming throughout the initial hour in the penumbral stage so you need to monitor exposure. You might use some ND during the brightest stage then take it off and open up all the way for the black-out as you may be able to pick up the sometimes red or amber glow it might have in this stage. I'd let it overexpose by two stops from your spot. (How old is that 800asa film?)

Another one is the earth's rotation. You will have to keep the moon in the frame as it drifts so you'd need a great tripod or tracking mount like some telescopes use.

East coast times are about 10-11pm and West coast is 7-8pm, Wednesday night, for the black out (totality) stage. The subtle waning period should start an hour or so before those times.
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#8 Jonathan Bowerbank

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Posted 20 February 2008 - 01:32 AM

Hopefully it won't be too overcast & rainy here in San Francisco. I plan on breaking out the SLR camera with the 200mm lens and 2x converter for this one :)
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#9 Tom Lowe

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Posted 20 February 2008 - 01:56 AM

I seriously wish I had a zoom right now to try shooting a timelapse of this. Then again, the weather is bad here in so cal, so I don't know how clear it will be.
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#10 Walter Graff

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Posted 20 February 2008 - 07:47 AM

you may be able to pick up the sometimes red or amber glow it might have in this stage


Don't forget the turquoise and blue! In case anyone wanted to know, the reason the moon turns shades of orange/red/turquoise and blue during an eclipse, it has to do with the earth and a lens effect. As the earth shadows the moon, the lower and upper atmosphere come into play. First the layer of air around the earth which is filled with dusk particles causes the red and orange hue. And depending on the condition of that dusk, is how red and orange you get. The lower atmosphere causes the color and the upper atmosphere act like diffusion and scatters that red color effect just as it does when the sun sets. A lot of folks notice the strange similarity in the orange huge of an eclipse and sunset. That is why. And then the upper atmosphere also comes into play from ozone. Ozone absorbs red freqeuncies at higher altitudes so just around the point of total eclipse you get the blue and turquoise edges of the moon. Imagine all this cool color effect with a mere 30 miles of the earths atmosphere.
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#11 Liam Dale

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Posted 20 February 2008 - 09:34 AM

Issues to consider: The moon will not suddenly go into eclipse. You may notice some dimming throughout the initial hour in the penumbral stage so you need to monitor exposure. You might use some ND during the brightest stage then take it off and open up all the way for the black-out as you may be able to pick up the sometimes red or amber glow it might have in this stage. I'd let it overexpose by two stops from your spot. (How old is that 800asa film?)



It's been frozen and I'm not exactly sure, but I know it's less than three years old.
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#12 John Sprung

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Posted 20 February 2008 - 02:32 PM

Here's the info on when and where the eclipse will be visible:

http://sunearth.gsfc...E2008Feb21.html

Scroll down to the middle to find the map. South America is the best place to see this one.



-- J.S.
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#13 John Sprung

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Posted 20 February 2008 - 03:08 PM

Your spot meter reads the correct exposure for an 18% grey surface. And as said earlier, its surface is quite a bit lighter than 18%. So stay true to that by overexposing a little to preserve the whiteness of the moon.


Actually, the moon is mostly darker than 18%. It looks bright white to us because we have nothing but the black of empty space to compare it with. It's like when you work a night exterior and you have a barn door cutting a light. The black inner surface of the barn door will look much brighter than the night sky behind it.

Here's some info I found about the reflectance of the moon:


The following is a list of the "visual normal albedo at 5% phase angle" of various lunar features. These numbers can be used to directly compare to terrestrial surfaces (reference cited below):

Darkest areas: 8.6%
Tranquillitatis south of Plinius: 9.1%
Plato's floor: 9.6%
Serenitatis east of Linne: 10%
Imbrium south of Plato: 10.4%
Nectaris: 11.4%
Ptolemaeus floor: 13.1%
Arzachel: 17%
Tycho ejecta: 20%
Aristarchus: 20%
Aristarchus interior: 22%
Bright spot in Deslandres: 24%
Proclus E wall: 28%
Stevinus A, Abulfeda E: 30%

These values are, as you can see, considerably higher than the other lunar albedos given. For comparison, the albedo of a green golf course is about 13%, roughly the same as that of the Cayley Formation which covers the floor of Ptolemaeus. So you see, the moon is not quite as dark as is often claimed - something about in the middle range of lunar brightnesses is just as bright as a grassy yard at noon.

Ref: British Astronomical Association, Guide to Observing the Moon, Enslow 1986



-- J.S.
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#14 Liam Dale

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Posted 20 February 2008 - 04:48 PM

Actually, the moon is mostly darker than 18%. It looks bright white to us because we have nothing but the black of empty space to compare it with. It's like when you work a night exterior and you have a barn door cutting a light. The black inner surface of the barn door will look much brighter than the night sky behind it.
These values are, as you can see, considerably higher than the other lunar albedos given. For comparison, the albedo of a green golf course is about 13%, roughly the same as that of the Cayley Formation which covers the floor of Ptolemaeus. So you see, the moon is not quite as dark as is often claimed - something about in the middle range of lunar brightnesses is just as bright as a grassy yard at noon.

-- J.S.


Thanks for you responses - but two follow-up questions.

I'm a still a little confused about how bright the moon is exactly. How much darker would you say, on average, the moon is than the typical 18%? (I'm not familiar with lunar geography, so I'm not sure which features listed above account for the majority of the lunar surface)

Also, do you have any idea how much darker the moon will be during the full eclipse? I would like to be able to capture the differant colors and would consider your suggestion of using an ND and then removing it during the full eclipse - but it seems that would create quite a discordance between the darkness of the half eclipse and the full. Not neccesarily a huge problem, but if it were possible to split the difference and overexpose the regular moon just enough that I would still be able to see the colors, that would be preferable.

Again, thanks for all the responses.

-Liam
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#15 Walter Graff

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Posted 20 February 2008 - 05:16 PM

"I'm a still a little confused about how bright the moon is exactly. How much darker would you say, on average, the moon is than the typical 18%? "


THis should help:

http://home.earthlin.../moonbright.htm
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#16 Liam Dale

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Posted 20 February 2008 - 05:26 PM

"I'm a still a little confused about how bright the moon is exactly. How much darker would you say, on average, the moon is than the typical 18%? "


THis should help:

http://home.earthlin.../moonbright.htm

man..now even more confused. The link suggests that long exposure times are a neccessity, but above I'm told I could shoot 24fps...
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#17 Valerio Sacchetto

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Posted 20 February 2008 - 06:38 PM

Sorry i didn't read the arcticle troughly but i noticed it expresses values in FC (illumination) and i glimpsed a "shooting by moonlight". That's different from shooting THE moon.
What's been said before is just right, you can shoot THE moon at 24fps 180°.
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#18 Matt Butler

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Posted 20 February 2008 - 07:50 PM

Last August we had a total lunar eclipse viewable from Sydney.
I spot read the event and my notes recall the wide exposure variations from start to finish.

Fully lit moon disc before commencement was T16 @1/60 100 asa.
Total eclipsed moon disc with just a slight *hot* leading edge was T1.8 @ 1/2 100 asa.
There was a very weak haze about that night.

That is an approximate 12 stop difference. I ended up filming a timelapse sequence, ( the entire eclipse took about 3 + 1/2 hours)
shooting * by twos* , ie. I frame set for the *hot* exposure and 1 frame adjusted for the weaker exposure and let the guys in post blend the final result.

Hope it's not all over by the time you get this!
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#19 John Sprung

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Posted 22 February 2008 - 01:17 PM

OK, so have you seen dailies? How did it work?



-- J.S.
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#20 Matt Butler

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Posted 23 February 2008 - 02:31 AM

OK, so have you seen dailies? How did it work?



-- J.S.


Looking at the actual rushes/dailies was a little strange because of the fact that when you *shoot by twos* the even numbered frames were exposed for the highlights ( the bright full moon disc) and the odd numbered frames were exposed for the shadows (the albedo/earthshine reflection).

This combination viewed during rushes projection gives you the effect of slightly under exposed shadow detail with washed out highlights resulting from the gross over exposure from the illuminated moon sectors occuring in the odd numbered sequence of frames.( The shadow detail)

How ever the even numbered frames hold the correct exposure for the fully lit moon and allow the fx folks to also pull a matte of their choice to achieve a realistic comping/blending of the two sets of exposure. (it's a sort of poor mans version of Extended Dynamic Range technique.)

It was a time lapse sequence which allowed exposure adjustment between frames.

That's how it worked and it was OK.
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