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Full Moon - Making Stars Stand out in the Sky?


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#1 Tom Lowe

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Posted 14 May 2008 - 09:32 AM

I'm going to be shooting long-exposure night landscape timelapses next week with a nearly full moon out, and I'm wondering if there are any tricks or filters or anything I can use to make the stars pop out a little more? Usually a full moon tends to drown out most of the stars.

Here's an example of shooting with nearly a full moon...


View on Vimeo

What would a pola filter do under these conditions, for example?
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#2 Jason Debus

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Posted 14 May 2008 - 10:18 AM

Unfortunately I don't think you can get both stars AND moon exposed like you want without some sort of controlled braketing exposure (more extreme than normal braketing) along with compositing in post.
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#3 Michael Nash

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Posted 14 May 2008 - 10:49 AM

Maybe a yellow filter to cancel out some of the blue sky?
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#4 Valerio Sacchetto

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Posted 14 May 2008 - 11:08 AM

Now this is just a thought. I don't know how feasible it would be but maybe it's worth a try especially if you're using digital.
You may try to make your own ND filter with clear glass/plexi/resin whatever with a round piece of nd gel attached or held between two pieces of glass. Since you're doing long exposures you can center the spot on the moon and then slightly move the filter to soften the edges and mask the imperfections the support may have. It'd be tedious as it can be but again...it's just a test after all. The principle would be the same as dodging in a darkroom (only the result would be like burning).
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#5 Walter Graff

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Posted 14 May 2008 - 11:39 AM

Simply too much contrast to do it in one shot. The moons brightness is about -8 to -12 depending on the phase so perhaps not such a full mooon would bring you closer to star field exposure since the moon is not as bright in lesser phases. But even then stars range from -1.5 to 8.5 (higher is dimmer on a stellar magnatude scale) so the discrepency of magnitude of stars to the moon
(-12 for a full moon to -1.5 for the brightest star in the sky and most stars aroud .4, each magintude becomes multiples of the last ) is simply too great for a simple exposure. You could fake it by shooting the same sky during a new moon and then shooting the moons timelapse and combine them by keying the moon into the sartfield.
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#6 John Sprung

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Posted 14 May 2008 - 12:37 PM

Moonlight is just sunlight reflected off a gray surface. It's not polarized, nor are the stars, and the color is neutral. So, filters won't help. The other issue on a really long exposure is that the stars move across the sky, and become streaks. So, I'd suggest shoot with the moon, expose for the moon, and matte in the stars. Would random stars be OK, or do you need to be astronomically correct?



-- J.S.
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#7 David Mullen ASC

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Posted 14 May 2008 - 12:55 PM

It's too extreme, like shooting into a spotlight... plus a full moon sometimes washes out the atmosphere so it's often hazier.

It's why in space photography, you can't expose for the stars and the Earth and Moon in one shot, so you never see stars in space shots of things like the space shuttle, etc. orbiting the Earth. The Moon is basically lit by the sun, so the exposures are close to daytime exposures.
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#8 Michael Lehnert

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Posted 14 May 2008 - 02:00 PM

I have actually tried exactly this set-up during last month's moon phase to test for a specific planetary constellation disappearing soon for the next 7 years. It was in the Midlands, away from city stray-light, at Jodrell Bank Observatory.

Attempts to have both subject matters exposed appropriately failed, as I originally feared by making theoretical calculations. The moon overhazed and fogged most stars, irrespective whether filming with it in the frame or filming in the opposite direction. So I can attest to what David, John and Walter said. Filtering is pointless as the glass has no effect on the physical set-up of what you are filming.

Check out Godfrey Reggio's production notes for his -quatsi trilogy for some info.
But as it stands, your shooting brief, Tom, is a uncrackable nut without work in post.

-Michael


P.S.: Funnily enough, I had a Bauer A 512 super 8 camera last year on after-work holiday (yeah, yeah, I am a geek, so what?! :D ) shooting the sky at night without any moon, in Spain. The camera has a nifty auto-exposure time-lapse flip-out measuring cell slaving the camera transportation, and the resulting time exp shots on 7217 & Plus-X are utterly gourgeous, with beautiful streaks or (if cam is motor-moved accordingly) beautiful pinhead stars. I wished you could just flip out such a cell on an Aaton or Arri for achieve such results with such ease!
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#9 Tom Lowe

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Posted 14 May 2008 - 02:15 PM

Sorry guys, I should have been more clear. I am not looking to get the moon into the shot with the stars, I am just worried about the massive ambient light from the moon drowning out the stars. 95% of that clip I posted doesn't actually include the moon, but it's so bright that it really lights the atmosphere blue and drowns out the stars. Again, sorry for my vague wording in the OP.

Wouldn't a pola block out some of the atmosphere reflecting the moonlight maybe?
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#10 Jamie Metzger

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Posted 14 May 2008 - 02:22 PM

I shoot a lot of star trails and timelapse. The timelapse that you posted a link to, had the moon in the frame for a few seconds, which makes sense because the moon is so much brighter than the stars. It would have been hard to look at for a longer period of time. Also, the moon "moves" at a different speed than stars are perceived to be moving.

One thing to remember, is that stars are specular; you do not need to shoot wide open for a really long time to see major constellations.

The guy who shot the timelapse, who you linked to shot with a still camera, probably hooked up to a laptop. I'm sure he tried a bunch of different exposures to see what worked best and went from there. You should try the same.

To get a good long exposure on stars, it's best to shoot on a night that has no moon.
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#11 Tom Lowe

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Posted 14 May 2008 - 02:46 PM

Jaime, I shot that myself on a 350D a couple weeks ago. I didn't even mean to get the moon in the shot, but it was sitting there in my frame when I was ready to go so I gave it a try.

I just pulled out a couple of screencaps from Baraka. I think all of the night timelapse in that movie was shot with ambient moonlight. Looking at these screencaps, the sky is such a rich, deep blue that it almost makes me think that Fricke might have used polas. I have no idea for sure whether he did.

Posted Image

Posted Image

Just out of curiosity, does anyone here know Fricke? Is anyone here working on Samsara by any chance?
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#12 John Sprung

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Posted 14 May 2008 - 07:22 PM

Wouldn't a pola block out some of the atmosphere reflecting the moonlight maybe?

It depends where the moon is relative to the part of the sky in your frame. If you're shooting close to the moon, with its light coming in close to perpendicular to the atmosphere, polarization wouldn't happen, so the filter wouldn't help. The steeper the angle of the moonlight to the top of the atmosphere, the more polarization you'd have. Polarization would help with a clear sky, but not with scattering off of haze.




-- J.S.
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#13 Tom Lowe

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Posted 14 May 2008 - 08:00 PM

What is causing the blue sky? Isn't it scattering of light from the moon?
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#14 James Steven Beverly

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Posted 15 May 2008 - 01:39 AM

What about using a graduated filter or a custom made center spot filter with the gray ND and/or Pola at the center and the surrounding in optical clear glass. The stop would be for the stars and the ND rating would be set from that. Basically the negative of this:

http://www.cokin.co....ages/cspot1.htm

(last one at the bottom) It might solve your stop problem, though the atmospheric light diffusion from the moon will still make the stars a little dimmer and harder to see. Just a thought. B)
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#15 James Steven Beverly

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Posted 15 May 2008 - 01:51 AM

The amount of light diffusion and haze coming from the moon should depend on how much water and dust is in the atmosphere and if there are upper atmospheric winds at the time, Winter would be your best bet when it's cold, dry and the air is stable. B)
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#16 Walter Graff

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Posted 15 May 2008 - 01:59 AM

What is causing the blue sky? Isn't it scattering of light from the moon?


It's called sky glow. The night sky has color but you can not see it as the level of light is too low for your eyes to register the color. In general, your eye is about 1/20 as sensitive to blue as it is green and red and that is because evolution taught us that blue is good so our eyes developed to naturally filter blue. The moon is like a baby sun so it's light also reacts with the atmosphere creating a mini daylight sky scenario, just far too dark to see it without long exposures. That glow you see is ionized oxygen found in the uppermost atmosphere at 540nm and 630nm wavelengths. Without it, we wouldn't be on this planet so it might not seem nice in the photos but crucial to our survival. In astrophotography we use IDAS LPS filters to help eliminate both this glow and other unnatural forms of light pollution. These are light pollution filters that help eliminate such annoyances on long exposures of deep space. I wonder if one would help you in your quest. But then again you need to use longer focal length lens with these filters or they actually interfere with how the lens sees when using wide lenses.

Want to try something cool that I just did this winter? http://www.colormoon.pt.to/
Shoot the moon on a high rez still cam, process it, and blow it up. I have a large print framed in my office and never get bored looking at it.
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#17 Matt Butler

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Posted 15 May 2008 - 02:56 AM

If you want subtle colour in your stars you have to shoot a couple of days either side of a new moon. Otherwise the excessive moonlight over exposes the night sky and you end up with white points for stars.

The material from Baraka looks like it has been shot on tungsten film with no 85 correction for the reflected "daylight" from the moon several days on either side of a full moon.

Attached is a clip of the Milky Way I shot under "dark sky" conditions. ie. no moon.


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#18 Matt Butler

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Posted 15 May 2008 - 04:01 AM

My apologies - the quality of the previous Youtube download is dreadful!

Try this version please.


View on Vimeo
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#19 John Allen

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Posted 15 May 2008 - 11:17 AM

The only way I can think of is by exposing for the stars, but then that's gonna leave your moon looking kinda flat.
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#20 Jim Keller

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Posted 15 May 2008 - 05:12 PM

I'm going to be shooting long-exposure night landscape timelapses next week with a nearly full moon out, and I'm wondering if there are any tricks or filters or anything I can use to make the stars pop out a little more? Usually a full moon tends to drown out most of the stars.

Here's an example of shooting with nearly a full moon...


View on Vimeo

What would a pola filter do under these conditions, for example?


We have quite a number of astrophotographers here, and I've been assured that the only way to do it is to expose once for the moon and a second time for the stars, and then composite. :(
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