Photo tips, tricks and my latest captures

Archive for March, 2013

Photographing the Milky Way Galaxy.

The Universe and Beyond by Terrence Dickinson is one of my favorite astronomy books. After reading the book, I was fascinated by the complexity and mystery of the universe. I started researching and found out that I can take milky way shots with the equipment I already have.

Joshua Tree forest with milky way in the background.

harshaj_130207_91blogD800, 16-35/F4 at 19mm, iso 6400, 30 seconds

Here is a shot of Old Faithful under the milky way taken during my recent trip to Yellowstone.

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D800, 16-35/F4 at 16mm, iso 6400, 30 seconds

Milky Way is our own resident galaxy. It is 10 billion years old. The sun is located in one of the outer spiral arms, 27,000 light years from the center. From edge to edge it spreads over 90,000  light years. The bulging disk at the center is 10,000 light years thick.  It is home to about 200 billion stars. The center of the galaxy is a giant black hole. Milky way is clearly visible in a moonless night.

If you’re lucky you may even see the andromeda galaxy, the only other galaxy visible to the naked eye. It is about 2.4 million light years from earth.( one light year = 6 trillion years)  In the above image  the andromeda galaxy is seen in the upper right part of the image at the edge of the frame. Our galaxy and the andromeda galaxy belongs to what is called the local group that contains about 50 other galaxies.

The Andromeda and the Milky Way galaxies are  on a collision course and speeding at each other at 1.2 million miles an hour. NASA projects that in 4 billion years from now  the two will crash head on . I hope I live to see the fireworks when that happens.

http://www.huffingtonpost.com/2012/05/31/milky-way-andromeda-galax_n_1561289.html

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Death Valley National Park, D800, 16-35/F4 at 16mm, iso 6400, 30 seconds

Milky way is best seen in summer months. At this time of the year we are looking  towards the center of the galaxy and away from it in the winter. However to really see the spectacle of milky way you may have to drive an hour or two away from the nearest city. Wait another 20 minutes to allow the eyes to adjust to the darkness.

A compelling image of  the Milky Way  can be made  without fancy equipment .

1. Equipment.

You need a DSLR. Newer full frame DSLRs can handle noise well and better suited for this kind of work. Crop sensor DSLR will still work but noise can ruin the image if you raise the iso too high. Fast wide-angle lens is the next requirement. I would recommend a lens with at least 24mm wide. Wider is better. I used my 16-35/F4 lens at 16mm for the above shot. Because the stars are so faint, the lens need to gather much light as possible. F2.8 lens is perfect but F4 lens will do too. Use the self timer or a cable release to avoid camera motion. Sturdy tripod is a must. Head lamp is useful to see and adjust the camera setting in the dark.

2. Location.

Find an area that is away from light pollution and city lights. Here is a link to Dark sky finder that helps to find the darkest areas in North America. It is an overlay of  a light pollution map on the google map of North America.  http://www.jshine.net/astronomy/dark_sky/

The Photographer’s Ephemeris (TPE) is program that can be useful. It will tell you the times of sunset/sunrise and moonrise/set.

For brighter skies time your shots during the new moon.

Presence of foreground elements make a better shot. This could be a tree, a mountain range or something iconic like old faithful.

3. Settings.

The idea is to get much light as possible to your sensor. Try the highest ISO that your sensor can handle before noise creeps in. In the above example I used ISO 6400 on my nikon d800. You may be able to getaway with ISO 3200 in a moonless night. Use the largest or the widest aperture available on your lens. To avoid star trails the shutter speed needs to be less than 30 seconds. A good way to find out the longest shutter speed you can get away without star trails is to divide 600 by your lens diameter. For instance if you use a 24mm lens the maximum shutter speed you can use is 600/24= 25 seconds. This calculation is for full frame sensor. If you are using a crop camera make adjustments( even shorter shutter speeds). Turn on your long exposure noise reduction in your camera menu. Shoot raw.

However if you are more ambitious and planning to print big, you need  a camera mount that track the earth rotation.(equatorial tracking mount).  This allows you to use a lower ISO and a longer exposure for brighter and better quality images. AstroTrac TT320X-AG is   a reasonably price  mount that sell for about $550.  Another more compact mount that sell for $399 can be found here http://www.bhphotovideo.com/c/product/915892-REG/iOptron_3300B_SkyTracker_Camera_Mount_with.html.

4. Technique..

Set the camera to manual mode. Set the aperture and shutter speed manually. I usually use the bulb mode and time the exposure using my watch or cell phone. In the above picture, the settings were as follows. F4, 30 seconds and ISO 6400. On your lens turn off the AF and set the focus ring to infinity. Use a piece of tape on the focus ring so it wont accidentally rotate. Use a remote trigger or self timer.

5. Test shots.

Take few test shots. To save time, increase your iso to say 24,00 or 51000 and expose for 10 seconds. Don’t pay attention to the quality of the image. Your are now trying to compose the shot. Pay attention to your foreground elements and the horizon.Once you are satisfied with the image go back to the recommended settings.

6. Post processing may need curve adjustments, selective sharpening and noise reduction.

7. Useful accessories

Head light, cable release, tape, watch ,tripod and ball head.

Smartphone apps night sky and star walk (http://vitotechnology.com/star-walk.html)k can help you navigate the dark sky. I use sky walk. You can point the smart phone or iPad to the sky during day time when scouting the location. The projected position of stars and the milky way at a given time is shown on the app which is very useful in  planning the shot.

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Here is another milky way image taken in Badlands National Park, South Dakota.

Clear skies.

Harsha