Peter Bargh shows you how to do Star Trail photography with your Pentax camera.
Posted: 11/11/2011 - 13:29
Now is an ideal time to do star trail photography as darkness comes early in the evening and the crisp autumn evenings often provide clear skies for full star patterns.
Stars don't move but the earth rotates on its axis so they appear to do and by shooting long exposures you can record the changing position as a trail.
There are two ways of taking star photos, one is to shoot a single exposure over a number of minutes, the other is to take a series of shorter duration photos and blend them together.
We will look at the latter as this method provides greater control of the exposure, especially of land objects that you may want to include that could become over exposed with a single longer exposure.
First off lets look at the location. I find it best if you have something on the ground to give the photo some foreground interest. An old ruined building, monument, interesting shaped tree or rock are ideal. Even better if they are away from city lights. The best shots are taken in more remote locations - on the moors, in the countryside or up hills/mountains. You need to be able to find your way back once you've taken you shot, so take a good torch and ideally shoot near an easy to follow path or you could get into trouble. I did some on Stanage Edge in Derbyshire recently and found the path back quite tricky to navigate while managing the torch, camera bag and tripod.
Gear
Any camera with a 30sec exposure or B-setting can be used. The camera must be able to take one shot straight after another. This is an important point as not all Pentax SLRs can be used successfully. For example, more modern digital SLRs such as the K10, K20 and K7 have noise reduction. This automatically processes the image after its taken to reduce noise. With a 30second exposure the processing can take a further 30 seconds to complete, but you can't take a photo while the camera is processing.
On the K10 you can go into settings and turn this auto mode off. Go to page 3 of the Custom Setting menu to find an option to set Noise Reduction on or off. This was removed on the K20 so the camera is not good for star trails. It was put back on the newer K7.
You need a tripod to mount the camera solidly in position and to save you having to sit and press the shutter at regular intervals you could buy a remote timer, ideally one with an multiple exposure feature. With one of these you can present a number of shots and leave the camera to it.
If you don't have a remote control you will just have to fire the shutter with your finger and then wait until you hear the shutter close and repeat the process. If you're doing a one hour trail this can be quite boring as you have to fire the shutter 120 times.
A wide angle lens such as the Pentax 12-24mm is ideal to get a good amount of foreground detail in but also plenty of the night sky.
Torch (I use a Joby GorillaTorch) or flash to paint light into the foreground subject (if it's close enough)
Warm clothing, something waterproof to sit on (I use a ground sheet and a rug to keep me warm.)
Technique
Choose your spot, making sure you include the North celestial pole (close to North Star/Polaris) if you want a circular trail. The further you are away from this the straighter the star trails. I look for Ursa Major and have that in the left of the frame as Polaris is above and to the right so I know I'm going to get a good pattern.
Get comfortable...you're going to be there for an hour. Wrap up warm, place the ground sheet on the floor and a rug on top to give you a warm base.
Step by step
- Set the lens to its widest focal length if you're using a zoom and frame up.
- Switch to manual focus and set the focusing to infinity
- Switch to manual exposure and set an aperture of f/4 and the shutter speed to 30 seconds (not 1/30sec)
- Set the ISO to ISO100
- Go into custom functions and make sure Auto Noise Reduction is turned off.
- Connect your remote release
- Get your torch or flash ready
- Trigger the camera
- Use the torch or flash to illuminate the foreground
- Check the result to see if the illumination is correct. If it's too strong speed up the torch painting or move the flash further away from the object. If it's too weak do more torch stokes, or fire the flash several times to build up the exposure. Repeat your tests until the foreground looks good.
- Use the LCD magnifier to check that the stars are visible.
- Take your first main photo using the revised illumination technique
- Now take a series of shots one after the other to record the movement of the stars. A trail of half an hour to one hour is good (60-120 30sec exposures).
You can blend the photos to make your star trail either manually in an image editing program such as Photoshop or PaintSHop Pro providing it has layers. Just open each photo and copy and paste as a new layer on top of the illuminated first shot. Set lighten as the layer blend mode and the trails will join together. Alternatively you can download a free automatic star merging program such as StarStaX
Members photos with related tags: star,trails
Add Comment
To leave a comment - Log in to Pentax User or create a new account.
3 posts
15 years