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Stars & Star Trails

q

Stars are easier than star trails.

Start with stars.

Stars

You can easily photograph a starry sky if you're away from city lights.

Which Camera Type?

Go to Digital SLR.

Go to Point-and-shoot.

Digital SLR

Suggested Exposure Settings

Here are some suggested exposure settings, at ISO 800, with a focal length of 50mm.

The settings are starting points.

Experiment!

ISO 800

  f/1.4 or f/1.8 f/2 f/2.8 f/4
Shutter Speed 4 sec. 8 sec. 15 sec. 30 sec.

Photograph the Stars

Do the following.

1) Use a tripod, or set the camera on a pillow, bean bag, or ?

2) Set the white balance to the Daylight setting, the sun icon.

3) If you're using a variable-aperture zoom lens (most zooms), use a wide-angle focal length, such as 18mm.

A wide-angle focal length lets in more light.

4) Focus on something far away, and then switch the lens to manual focus using the switch on or near the lens.

Don't confuse the M of manual focus, with the M of manual exposure on the exposure mode dial.

Locate the manual-focus ring on the lens.

The manual-focus ring isn't the zoom ring.

The zoom ring changes the lens focal length.

The manual-focus ring, which is often at the end of the lens, is narrower.

You may need to tape the manual-focus ring to keep it from shifting during long exposures.

5) Set the exposure mode dial to M, Manual exposure.

6) Set the lens opening and shutter speed to the above values.

Some cameras have one control knob, other cameras have two control knobs.

 One Control Knob
Lens Opening

If your camera has one knob, press and hold the button with the aperture icon, and move the knob.

Shutter Speed

If your camera has one knob, move the knob to set the shutter speed.

Two Control Knobs
Lens Opening

If your camera has two knobs, move the knob that controls the lens opening.

Shutter Speed

If your camera has two knobs, move the knob that controls the shutter speed.

7) Trip the shutter with the camera's self-timer, or a remote release.

Go to Useful Information.

Point-and-shoot Cameras

Your point-and-shoot camera must be capable of manual exposure.

Check your camera instruction manual for how to set the lens opening and shutter speed.

Suggested Exposure Settings

Here's a suggested exposure setting at ISO 800.

The setting is a starting point.

Experiment!

ISO 800

  f/2.8
Shutter Speed 15 sec.

Photograph the Stars

Do the following.

1) Use a tripod, or set the camera on a pillow, bean bag, or ?

2) Set the white balance to the Daylight setting, the sun icon.

3) Zoom the lens to a wide focal length.

A wide-angle focal length lets in more light.

4) Focus on infinity.

Your camera may have a button that cycles between flower and mountain icons.

If so, use the mountain-icon setting.

5) Set the exposure mode dial to M, Manual exposure.

6) Set the lens opening and shutter speed to the above values.

7) Trip the shutter with the camera's self-timer, or a remote release.

Useful Information

Stars Are Point Light Sources

Because stars are point light sources, exposure is determined by the actual area of the aperture, not by the lens opening.

Lens opening, the f/stop, is a ratio of the focal length and the lens opening number.

Lens opening is not the area of the aperture.

For example, a 50mm lens at f/1.4 will give the same exposure as a 100mm lens at f/2.8, of a point-light-source subject.

That's because the area of their apertures are the same.

On the table below, look for the two 1002 values.

The red area values are for the above example.

Other values with like colors will also produce the same exposure, as the areas are the same.

The areas below are square millimeters.

Go to What's a f/stop?.

  18mm 25mm 50mm 100mm 150mm 200mm
f/1.4   250 1002      
f/2   123 491      
f/2.8 32 63 250 1002 2254 4007
f/4 16 31 123 491 1104 1963
f/5.6 8 16 63 250 564 1002
f/8 4 8 31 123 276 491
f/11 2 4 16 65 146 260
f/16 1 2 8 31 69 123

The values are from Peter Cox's Aperture Area Calculator.

Aperture area is computed using the following formula.

Area = Pi (f/2N)2

Where f is focal length and N is the f/stop number.

Star Streaks - Too Long of a Shutter Speed

The stars will become streaks with longer shutter speeds.

The shutter speed needed to prevent streaking varies according to the focal length.

The apparent movement of the stars across the frame will be less at a wide-angle focal length, and more at a telephoto focal length.

Therefore, as the focal length increases, the shutter speed must increase.

Use the following formula to determine the maximum shutter speed for avoiding blur.

1,000 ÷ Focal Length = Maximum Shutter Speed

Focal Length

Maximum

Shutter Speed

(Seconds)

18mm

56

24mm

42

50mm

20

100mm

10

150mm

7

200mm

5

300mm

3

More Stars

You'll get more stars when using wider lens openigs.

And, if you use a wide-angle focal length, with its concomitant longer possible shutter speeds, more stars are recorded.

Focal Length

Shutter Speed

(Seconds)

# of Stars

18mm

56

More Stars

 

 

 

 

 

 

 

 

 

Fewer Stars

24mm

42

50mm

20

100mm

10

150mm

7

200mm

5

300mm

3

Reduce Noise

Your camera may have a long-shutter speed noise reduction feature.

Check your camera instruction manual.

Star Trails

Use a digital SLR camera for star trails.

A Great Foreground Is Required

Star trails all by themselves are boring.

You need something in the foreground that adds to your photograph.

Look for:

• A tree.

• Rocks.

• Flowers.

• An industrial landscape.

• Your tent illuminated inside by a flashlight.

•  Or ?

You can add light to the foreground by choosing the right time of day, to be described below.

Or, add light with a flashlight, flash, car headlights, or ?

Go to Painting with Light.

But, when you're first photographing star trails, don't worry about the foreground.

Three Sky Conditions Are Required

Sky Condition #1 - Darkness

Light Pollution

Most people live in or near a city.

So, night isn't night, for most photographers.

You have to travel away from cities to do star photography.

If you can see the Milky Way, it's dark enough.

Moon

A crescent moon can be photographed with stars, as it's brightness is closer to that of stars.

A full moon is very bright, and stars are very dim.

You can't photograph both at the same time.

Sky Condition  #2 - Clear Sky?

A clear sky is usually preferred.

High clouds can add a hazy look, though.

Check the weather.

Sky Condition #3 - Low Humidity

The stars will be more clear if the humidity is low.

Seven Things to Bring Along

Bring along:

1) A flashlight and/or a head-band light.

A red-light setting on the head-band light reduces the time it takes for your eyes to reacclimatize to darkness.

2) A timer with illumination.

4) Some hot or cold drinks, and snacks.

5) Some entertainment, such as a Book, music, DVD, and so forth.

6) A cushion, chair, or sleeping bag.

6) A friend or significant other.

7) A tripod.

A tripod is not required, but certainly is handy.

Without a tripod, set the camera on a pillow, bean bag, or ?

When using a tripod, place something bright at the base of each leg, so you don't bump the tripod during the exposure.

Set Up Before Dark

Set up your camera and tripod, and compose the image, before it gets dark.

Otherwise, you won't be able to see through your camera.

If you don't. the horizon may be crooked, there may something in the frame you didn't expect, and so forth.

Be sure you know the way back to your car in the middle of the night.

Camera Power

Charge your battery.

Long exposure times will consume battery power quickly.

If you have a spare, bring it along.

An external battery is preferred, such as one located in a hand grip for the camera, or a battery like the Digital Camera Battery.

The optimum power supply is an AC power supply.

Use a long extension cord, or an inverter connected to your car's 12v power outlet, such as the cigarette lighter.

Seven Camera Settings

Camera Setting #1 - Quality

Save your photographs using the raw file format.

You'll be able to tweak the exposure more effectively.

If your camera doesn't have the raw file format, use the highest quality JPEG file format setting.

Camera Setting #2 - Focal Length

Realize that when you zoom your variable-aperture zoom lens (most zooms), the lens opening can change by one stop.

Let's say you have a zoom that goes from 18mm, wide angel, to 70mm, telephoto.

If you're at the wide-angle focal length of 18mm, and zoom to to the telephoto focal length of 70mm, the lens opening changes by one stop smaller (less light).

Camera Setting #3 - Focus

Focus on something far away, and then switch the lens to manual focus using the switch on or near the lens.

Don't confuse the M of manual focus, with the M of manual exposure on the exposure mode dial.

Locate the manual-focus ring on the lens.

The manual-focus ring isn't the zoom ring.

The zoom ring changes the lens focal length.

The manual-focus ring, which is often at the end of the lens, is narrower.

You may need to tape the manual-focus ring to keep it from shifting during long exposures.

Camera Setting #4 - Image Stabilization

If your lens has image stabilization, turn it off.

You'll save power, and may eliminate a shift in the focus during long exposures.

Camera Setting #5 - Mirror Lockup

When using mirror lockup, the first press of the shutter release flips the mirror up.

Then, with this vibration source eliminated, a second press of the shutter release opens the shutter.

Because star-trail photographs use long shutter speeds, there's no need to lock the mirror up.

Camera Setting #6 - White Balance

Use the Daylight white balance setting, the sun icon.

The tungsten setting, the light-bulb icon, will add blue to the scene.

If you're saving the photographs using the raw file format, you can set the white balance when you process the files.

Camera Setting #7 - Exposure

ISO

Set the ISO to a low or medium setting.

Higher ISO settings will have more noise, making the black night sky gray with anomalous specs of magenta and green.

Newer cameras will have less noise than older cameras.

Experiment with higher ISO settings.

Set the exposure mode dial to M, Manual exposure.

Lens Opening

Set the lens opening to f/4.

As mentioned, wider apertures will produce brighter star trails, and smaller apertures, darker star trails.

Shutter Speed

Experiment with shutter speeds between ten minutes and one hour.

The star trails will be longer with longer shutter speeds.

If there's light pollution, use shorter shutter speeds.

Go to Bulb Shutter Speed.

Suggested Exposure Settings

Here are some suggested exposure settings, at ISO 200, with a focal length of 50mm.

ISO 200

  f/1.4 or f/1.8 f/2 f/2.8 f/4
Shutter Speed 8 min. 15 min. 30 min. 60 min.

Programmable Remote Releases

If you pursue star trail photography, you may want to purchase a programmable remote shutter release.

During the Exposure

Cold

If it's cold, keep spare batteries inside your coat.

Avoid breathing on the camera to prevent condensation.

Dew

Dew may form on your lens.

Try:

• A lens hood.

A lens hood also blocks the light from your flashlight and head-band light.

• A Giotto Rocket blower.

• A battery-operated fan.

• A hand warmer.

• Placing the camera and tripod inside a tent, with the lens protruding through the zipped-up door.

• A heating device like those from Kendricks.

After the Session

If, when you're finished, the camera will be going from the cold outdoors into the warm indoors, prevent condensation from forming.

Put the camera in a plastic bag until it warms up.

Four Exposure Factors to Consider

When You're More Experienced

Exposure Factor #1 - Length of Trails

During twenty-four hours, stars "turn" in a complete circle.

A circle is 360 degrees.

360° ÷ 24 Hours = 15°

So, star trails will be 15 degrees in length for every hour of exposure.

You'll want to expose for at least one hour, and probably, longer.

Exposure Factor #2 - Circles or Arcs

Circles

If you're in the northern hemisphere, point your camera at the North Star (Polaris) to produce circular star trails.

This is because the North Star is on the Earth's rotational axis.

To find the North Star, locate the Big Dipper in the sky.

The two stars that form the side of the basin, at the end of the dipper, point to the North Star.

The North Star is the last star in the handle of the Little Dipper.

Go to The Big and Little Dippers.

Arcs

When you point your camera away from the North Star, the star trails will appear as arcs.

Exposure Factor #3 - Time of Day

Fill Light

You can use late or early light as fill light for the foreground.

Also, the sky may be more blue.

Start the exposure about ninety minutes after sunset or before sunrise.

Likewise, start the exposure about sixty minutes after moonset or before moonrise.

Airplanes

There's less chance of an airplane flying across the frame after 2:00 A.M.

Exposure Factor #4 -

Stars at the End of the Trails

By having the stars at the end of their trails, the constellations will be visible.

To produce stars at the end of the trails, use a small lens opening for the main exposure.

Then, block the lens, without disturbing the camera, for about five minutes.

Finally, uncover the lens without disturbing the camera.

Expose for about five minutes.

This will create a small gap between the trail and the star.

Light Pollution Filters

If you're doing lots of start photography, consider using light-pollution filters.

Go to Jerry Lodriguss' Filters for Astrophotography.

Stacking Star Trail Photographs

You can take multiple exposures, one-after-another, of the sky.

Then, you "stack" them with a specialized program, or with Photoshop or Photoshop Elements.

Photographs made from multiple exposures have less noise.

Stacking Programs

DeepSkyStacker

Image Stacker last updated in 2005

Startrails

Star Trails Photoshop Action Last updated 2006

Stacking Tutorials

Stacking Star Trails: Tips & Techniques Harold Davis, 2008

How To: Star trails – Stacking with StarTrails.exe Adam Currie, 2009

Star Trails, Digital Style; Exposure and Stacking Techniques Art Rosch, 2007

More

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Complete Sun and Moon Data for One Day U.S. Naval Observatory

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timenaddate.com:

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Moon Phases for UTC

Sunrise and Sunset Calculator

Star & Star Trail

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Photographing Star Trails Dan Heller

Star Trails Flickr group

The Twilight Hour – Photographing Star Trails and Static Stars Floris van Breugel