The Art of Science / Discuss

kasi metcalfe says:

Star trail photographs are easy to produce and can give striking results.


chiricahua star trails by Ken Rappart
www.flickr.com/photos/kreppart/36958378/

Since the earth rotates the sky appears to move more or less towards the west. As the world turns in relation to the stars a long exposure picture will result in the stars making 'trails' in the picture. The longer the exposure, the longer the trails will be.

EQUIPMENT:
- A camera that can hold the shutter open independently for a long period of time. (I like to use a manual SLR set on B or 'bulb')
- Cable release
- Tripod
- Patience
If using a digital: Consider that it takes battery power to hold the shutter open, iso mode, pick the lowest to reduce noise.
If using film: A lower speed is best suited (ie 100 iso)

COMPOSITION:
Your exposure and lens choice will effect your composition, so if you have a strong idea of what you want to capture first it will make picking an exposure time and lens easier. If not the only thing to do is experiment!

top of the dock by Swordfish7
www.flickr.com/photos/swordfish7/2549353156/

A few factors to consider:
- It is usually a good idea to get your horizon straight to get a bit of perspective.
- Include a bit of landscape, a tree, rocks, mountains etc, all up to you!

Star trails by Gidget's Photo Gallery
www.flickr.com/photos/gidgetsphotogallery/2562328029/

- If you want a silhouette leave your foreground objects dark, if not take a flash or torch to expose them. Keep in mind it's best not to have the foreground objects lighter than the star trails, leave them pretty dark so they don't take away from the stars but have enough detail to see what they are.
- How much of the sky do you want to see? A wider lens will show you more of the sky, it all depends on what you're trying to include in the photo landscape wise. The next best thing to experimenting yourself is to have a look at what other people have tried.
- What type of trails do you want? It depends on where you point your camera.

Star Trails by Matt Rodgers
www.flickr.com/photos/mattabilly/216235198/

The earth spins an on axis, if you photograph this point you get the circular motion. In the northern hemisphere it's relatively easy to find just point at the Northern Star, it's almost dead on this point. In the Southern it's a bit harder because there are no actual stars to mark the point of rotation. I've made a diagram to help:

When looking at the night sky draw a mental line from the top of the Southern Cross to the bottom, use this length as a measurement (1). Connect the constellation The Pointers (2) and draw a perpendicular line from this line (3). Time the southern cross measurement by three down and out (4). Where (3) and (4) intersect is where the Southern Celestial Pole (or SCP) is.
If you aim your camera at this point you'll get the circular rotation.

I took this one (one of my first trys) at 4 hours on a 35mm camera (FM2) with a 50mm lens with 100iso film and painted the tree with torchlight.

EXPOSURE:
Is all up to you!

Star Trail Over Paulinskill Viaduct by t3h_sw3d3
www.flickr.com/photos/t3h_sw3d3/581560501/
The above photograph was constructed in Photoshop. Where you take multiple images with a digital camera and layer them in photoshop. This one is 188 photographs, each at 30 seconds long. Making it possible to use a digital camera for star trails.


sand dune & moon light by by dreamranchu
KB canham wood field 4x5 72 mm XL, 30 mins at f8 on Fuji RVP 100F.
www.flickr.com/photos/panoramic_landscape/2802901818/

PROBLEMS:
- Clouds will block the stars can give an interesting effect at times but more often than not will ruin your photo so try to pick clear nights.
- Light pollution from street lights, buildings, cars can sometimes lighten the sky so lowers the contrast between the sky and stars. Try to pick a dark part of the sky away from populated areas. Having said that when used correctly lights can give really nice effects.
- Dew. On colder nights when your camera is set outside long enough dew can collect on the lens and camera. I used to cover the body with whatever I could find and check the lens for condensation. It is possible to construct a cheap lens warmer out of resistors and a battery into a ring shape that sits on the end of the lens: www.metacafe.com/watch/770007/diy_lens_warmer_heater/
- Tripod movement. Don’t bump or move your tripod at anytime when the shutter is open, it will interrupt the trails.

For more info:

www.weatherscapes.com/techniques.php?cat=astronomy&pa...

www.wildlifephotography.nl/content/view/129/198/
Originally posted at 8:59PM, 7 September 2008 PDT (permalink)
kasi metcalfe edited this topic 45 months ago.