Tips for Making a Star Trail Shot

There are some things that are absolutely essential for making a star trail shot.  You must have a tripod to hold your camera steady during the shot.  You must have a method of holding the shutter open for longer than 30 seconds.  Your battery must be able to keep the camera going for at least one hour, preferably 2 hours.

A good star trail shot needs a one-hour or longer exposure to make a good trail.  That means the camera can’t move during this time.  Your tripod must be sturdy and in a stable position.  An external weight, such as a bag of rocks, can be hung on tripod to give it more stability.  The exposure mode must be set to manual and the shutter speed to bulb.  In the bulb setting the shutter stays open as long as the button is pressed.  The shutter can be kept open with a cable release that can be locked with the button depressed or a cable release with an interval timer can be used.  Nikons that used the infrared remote will time out after 30 minutes.  For an exposure longer than 30 minutes you must use a cable release.  If your battery dies during the shot, you will get nothing.  You must be confident your battery can make it during the entire exposure.  Testing is one way to gain that confidence.  Set the camera up as if you are doing a star trail shot, but leave the lens cap on.  Do a one-hour exposure and see if the battery lasts and then do a two-hour exposure.  Past experience says that no-name batteries will not make it.  Mark your batteries that are capable of 1-hour continuous use and put a fully charged, good battery in the camera just before the shot starts.

Camera settings

Most cameras have a difficult time focusing in the dark.  That means the shot must be made with autofocus turned off.  The view through the viewfinder is rather dim in the dark, so the recommended method is to focus on something distant before dark and turn off the autofocus.  I like to tape the focus ring in place so I don’t inadvertently move it.  If you are using a zoom lens, changing the zoom can change the focus.  The zoom needs to be fixed and taped as well.  I like using a wide a lens as possible to show lots of stars.  Setting up your composition before dark while you can see is also a good idea.

There are two basic methods for creating a star trail shot.  One is to make one long exposure and the shot is done.  The other method is to make a series of shorter exposures and stack them in Photoshop.  So if you don’t have Photoshop or don’t want to do the stacking and blending then the choice is made.  The advantage of the stacking method is you can change batteries in the middle for really long exposures and if your battery dies all is not lost.  You can also blend different foreground shots with the start trails, such as light painting the foreground several times for different looks or the foreground at twilight.  I think there is less noise and the fainter stars show better with the stacking method, but a good shot can be made either way.

To noise reduce or not, that is a question that must be settled ahead of time.  To use the stacking method, long exposure noise reduction must be off, otherwise there will be gaps in the trails.  For a continuous one-hour exposure, the noise reduction period will be the same length as the shot, one hour.  Noise reduction must be set before the shot begins and the camera must remain on during this time.  So the total time the camera is on is two hours in this example.  If the battery dies during noise reduction you get nothing.  If you turn the camera off during noise reduction, you get the image without any noise reduction.

For a one-hour exposure a good starting point for exposure is f4 and ISO 200.  The histogram will show underexposed, but camera raw and/or Photoshop can be used to make adjustments.  For the stacking method I like to use a 5-minute exposure at f2.8 and ISO 200.  I use an interval timer to make the shots.  Again the histogram will appear dark, but stacking will progressively lighten the image.  Here is a reference on how to stack images - http://www.naturephotographers.net/articles0509/fv0509-1.html.

I like to shoot in RAW so I can change the white balance after the fact.  If I am stacking I may use a different white balance on the foreground shot than on the star trails.  If you are shooting JPEG, I would suggest setting to a color temperature of 3200K if you want a bluish sky for the stars.  Camera sensors can do funny things with a dark sky and many times the auto white balance will give a very yellow sky for a night shot.

Another thing to do is to set up before dark and make some test shots.  With these shots you are looking to see if the horizon is level and distant objects are in focus.  Is the balance between foreground and sky what you want?  A test shot after dark can show you placement of the North Star if you want a circular star pattern.  To make a quick test shot after dark raise the ISO to 3200 and set the time for 30 seconds.  You can also use a flashlight to illuminate a distant object to check focus.  If you use a flashlight you can use ISO 200 instead of 3200.

A shot with the North Star showing will create a circular pattern around the North Star.  Shooting to the East or West will create curving streaks.  The trail length will be 15 degrees for each hour.  I use a compass to find the position of the North Star before dark so I can compose the North Star where I want it.  The height of the North Star above the horizon is equal to the latitude, in the case of Lancaster 34.7 degrees.  Fine tuning can be done with test shots after dark.

Chris’s Check List for Star Trails

Test shot

1. Focus Camera on a distant object.
2. Turn off Auto Focus.  Tape Focus Ring. Tape zoom lens.
3. Turn off Noise Reduction if desired.
4. Turn off VR.
5. Set ISO to 3200 and exposure to manual f4 aperture and time to 30 seconds.
6. Shoot photo and check to see if horizon is level and composition is pleasing.
7. Redo composition and take more shots until satisfied.

Star Trail Shot

1. Focus Camera on a distant object.
2. Turn off Noise Reduction if desired.
3. Turn off VR.
4. Turn off Auto Focus.  Tape Focus Ring. Tape zoom lens.
5. Set Exposure to Manual aperture f4 and time– bulb.
6. Set ISO to 200.
7. Adjust cable release timer to 5 minutes/stacking or 1 hour/long exposure.
8. Change Battery to a “GOOD” battery if necessary.
9. Set up Lawn Chair.
10. Push Start.