Category: time lapse

Astrophotography: Anyone Can Do It

Meanwhile the Earth is spinning on its axis. Like the rotating restaurant on the top of a cheesy hotel we are constantly pointing in a different direction. That creates a photographic problem and opens a photographic opportunity!

A few nights ago I pulled “Clicky” out and shot the night sky. My intention was to produce a time lapse as the stars rotated by (at the bottom of this entry).

As I showed the video one thing became obvious. Many of those who saw it didn’t realize they’d see that effect from a camera in a fixed position. We’ve become out-of-touch with the nighttime sky which no longer is as visible nor has the importance it did to our great grandparents.

Stars are very, very far from us. The closest star (other than our own Sun) is Proxima Centauri which is about 25,260,733,353,600 miles away (that’s 25+ trillion miles)! Others in the visible sky are thousands or even millions of times more distant. That keeps our view of stars reasonably constant.

Meanwhile the Earth is spinning on its axis. Like the rotating restaurant on the top of a cheesy hotel we are constantly pointing in a different direction. That creates a photographic problem and opens a photographic opportunity!

The opportunity is time lapse. What my little movie shows isn’t stars moving, but the effect of the Earth rotating&#185. Aiming at any single point in the sky reveals stars passing by. They’ll return to about the same point 24 hours later.

The photographic problem is the same one faced any time you try to photograph something in motion: blur!

Because stars are dim the only way to photograph them is to keep the shutter open a long time and allow more photons to hit the camera’s sensor. The longer the shutter is open the farther those stars move. The result is streaks across the sky, not points of starry light.

Sophisticated astronomers (aka – not me) solve this problem with clock drives. Their telescopes and cameras move in exactly the opposite direction as the Earth. The effect is to hold the stars still.

There are simple mechanical devices that do exactly the same thing. I’ve got a little wooden wedge with a hand turned screw which allows my camera to take long star exposures with impunity.

Nowadays the easiest way to eliminate the blur is with a software assist.

When I shot my time lapse I took over 400 images one-after-the-other. Each was a single second’s look at the sky. Using a program called DeepSkyStacker I combined those images and restacked them eliminating the effect of Earth’s rotation.

As a bonus DeepSkyStacker looks at specially shot blank frames to understand my specific camera’s weaknesses and counteract them!

The resulting photo is the equivalent of an eight minute plus exposure–though digitally made superior.

I’ve taken a small piece of it an placed it at full resolution at the top of this entry. Just below it is the full frame (though not at full resolution). These shots, compilations of over 400 separate photos, show stars I couldn’t see with my naked eye.

It’s all very heady stuff and amazing to me. It’s not just that these techniques are available, it’s that they’re available to anyone for free and easily used with cameras a lot less sophisticated than mine.

&#185 – Here’s re-tweaked version of my time lapse nighttime sky movie from a few night ago.

Stars Over Hamden: Time Lapse Animation

I pointed the camera toward the sky. A few stars were bright enough to use to focus. This was going to be a 100% manually set shoot.

My intention was to go out and view Comet McNaught last night. For a variety of reasons (including disappointing results from others) I stayed home. Still, stars and sky were on my mind!

I pulled out the camera (aka Clicky), threw on my 70-200mm f/2.8 lens (Thanks again Santa… how do you know?), picked up my tripod and intervalometer and headed out to the deck. After yesterday’s hellish storms it was good to be outside on a clear, nicely breezy, warm night. The oppressive humidity of the afternoon was long gone.

I pointed the camera toward the sky. A few stars were bright enough to use to focus. This was going to be a 100% manually set shoot.

I pulled back the zoom from its maximum focal length down to 100mm then snapped off a shot at f/2.8, 1 second, iso 1600. I needed to make sure the camera would capture something. It did. Zooming in showed the picture was pretty sharp.

The one second shutter was a critical number. As you’ll see in the animation the stars move across the sky. Hold the shutter open too long and the stars will be streaky blurs.

My last step was setting the intervalometer. I set it to six second intervals which gave me ten shots a minute.

I let it run for around 45 minutes.

The finished product was run through Sony Vegas 9, a video editor. Levels were adjusted, but there’s an interesting conflict between stars and noise if you bring the gain up too much. That’s a technique probably only learned through trial and error.

Originally this was uploaded to Youtube. It was compressed so much the stars virtually disappeared. This method is a little better, but I’ll probably work on another method this weekend.

Late Afternoon Cloud Time Lapse

I parked myself across from my neighbor Joe’s house, pointed the camera skyward and sat down right in the middle of the road! We don’t get much traffic.

Talk about your wasted days! Sunday was totally devoid of anything meaningful.

Around 7:30 PM I decided to go out and do something… anything worthwhile. I carried my camera, a wide angle lens, tripod and intervalometer.

I haven’t shot any time lapse in a while. Shooting one today provided at least some intellectual exercise.

It didn’t take long to realize there aren’t many places on my street with a wide enough view to make this work. Watching Ross Ching’s work has made me more-and-more aware of the importance of shooting wide.

I parked myself across from my neighbor Joe’s house, pointed the camera skyward and sat down right in the middle of the road! We don’t get much traffic.

For the geeky: Canon 450d and Sigma 10-20mm lens at 10mm focal length, f/9, iso 100, manual focus, 5 seconds between each shot. Shooting was in aperture priority so the shutter length varied as the light diminished without affecting the depth-of-field. I assembled the whole thing in Vegas 9.