Can you photograph the Milky Way when there is a full moon?

Asked 8/14/2013

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Is it possible to photograph the Milky Way, stars, or other night-sky objects when a full moon is out? How much does moonlight affect astrophotography, and are there any situations where it still works?

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

13y ago

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With regard to reasonably bright stellar objects: technically, yes.
With regard to dimmer objects like those that make up most of what we mean when we say "The Milky Way": practically speaking, no.

In addition to the phase of the Moon, which determines the overall amount of light falling on the atmosphere above a specific location on the Earth's surface, photographing astronomical objects when the Moon is in the sky depends on several other factors. How much moisture is in the air in your location, both in terms of vapor and clouds? How much particulate matter (dust, pollen, pollution, etc)? How calm or turbulent is the atmosphere over your location? At what altitude are you located? Just as ground based light pollution is reflected and dispersed based on atmospheric conditions, so the light from the moon is spread across the sky. If you were in an extremely arid location, especially at high altitude so that the atmosphere is significantly thinner, you will be able to see and photograph dimmer objects than if you are at sea level under a very humid and turbulent sky. This is one reason why the world's largest and most expensive terrestrial telescopes are located in such places. In addition to lessening the effects of light pollution, those locations reduce the effect of the light cast by the Moon on the Earth. But they only reduce it, even when filters are used that allow specific wavelengths to pass while filtering most of the Moon's broad spectrum light. The most demanding deep sky work takes place at those locations on nights after the Moon has set or before it has risen.

Think about it. In Earth orbit the Hubble telescope can take incredible images of dim, far away objects without having to be in the Earth's shadow from the Sun and Moon. Even dim, far way objects that have a fairly small angular distance separating them from the Sun. The reason this is possible is because there is no atmosphere to reflect and spread out the light from the Sun in the space between the telescope and the dim object being viewed.

How brightly you expose also affects what is and what is not visible in a photo. The following photos were taken on a cold January evening when the atmosphere was fairly dry and the Moon and Jupiter were very close to one another. While not full, the Moon was about 2/3 illuminated.

This one is exposed properly for the Moon. Note dim Jupiter at the upper left. Jupiter + Moon

A crop of Jupiter from another exposure that overexposed some of the highlights of the Moon. Even though several of Jupiter's moons are in the field of view, they are not bright enough to be visible when exposure allows details of Jupiter's atmospheric bands to be visible. Jupiter

Another look at roughly the same field of view, but with exposure increased to allow the brightest of Jupiter's moons to be visible. Notice that surface detail of Jupiter is now completely blown out. Jupiter's moons

And a wider view of the same scene, exposed for the brighter stars and moons of Jupiter in the frame. Jupiter is in the center of the frame which is rotated ≈90° clockwise from the previous two closeups. Notice the lens flare from the Moon that was shielded by a makeshift hood extension when zoomed in on Jupiter. Also note that if the first photo above had been exposed at this level, the flare would have been visible in that photo as well. There were 12 stops difference in exposure between the first photo and this one. (Both were taken with a 400mm focal length. The first was cropped tighter). Moon-Jupiter-stars

If you were to add the much more humid air typical of a Summer evening in the location these were taken and a full Moon, nothing other than the Moon and Jupiter would probably be visible as the overall brightness of the sky from the diffracted moonlight would drown out the light from the stars, even if the lens was pointed to an area of the sky that didn't allow the Moon to cause lens flare. And none of the stars visible in this photo are as dim as most of the stars visible in impressive photos of the Milky Way.

Originally by user15871. Source · Licensed CC BY-SA 4.0

user15871

13y ago

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AI Answer

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A full moon usually makes Milky Way photography impractical. The Milky Way’s faint detail depends on strong contrast against a dark sky, and bright moonlight washes out that contrast much like severe light pollution.

You can still photograph brighter objects and some stars, but results depend heavily on atmospheric conditions such as humidity, haze, dust, pollution, clouds, and turbulence. Those particles scatter moonlight across the sky and create a bright veil that overwhelms dim detail.

So:

  • Milky Way core/dust lanes: generally no, not effectively with a full moon above the horizon.
  • Brighter stars or some brighter astronomical objects: sometimes yes, with limitations.
  • Wide night landscapes with a moonlit look: yes, but that’s different from classic Milky Way imaging.

Light-pollution or contrast filters offer limited help because moonlight is also broad-spectrum, so they won’t restore the lost contrast needed for Milky Way shots.

For best Milky Way images, shoot on moonless nights or when the moon is below the horizon, and choose clear, dry, dark conditions.

UniqueBot

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13y ago

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