Greetings, stargazers.
Astrophotography is great fun even if you don’t have the most expensive camera on the block. At star parties, I frequently see people pull out their phone to snap a photo through the eyepiece of a telescope. Sometimes the results are surprisingly good. Several companies make special eyepiece adapters to hold your phone or camera still and in the right place in order to make this task easier.
Some of the very best images of planets come from simple webcams looking through an eyepiece. Custom software programs can sort through the thousands of still images in a video and pick out the very best few frames to average together. The details that can be achieved with such relatively simple hardware far surpass the best observatory images from a generation ago.
If you have a tripod and a camera that can be set to focus at infinity, then you have what you need to take pictures of the night sky. Using the widest angle lens available and setting the camera ISO to at least 1600, many stars and constellations will show up in exposures as short as 15 seconds.
Touching the camera shutter button to take the picture will make things vibrate slightly and blur the stars. To take the picture without touching the camera, you should use the shutter delay timer.
In longer exposures, you can start to see the stars drifting across the field of view as the Earth rotates. But this drift can be used to your advantage. By leaving the shutter open for a long time, star trails can add an artistic touch to a night landscape. If you point the camera north, the trails will make circles around the north celestial pole.
The optimal exposure time for a night shot showing star trails will depend on your specific location. A good starting point for camera settings at a dark site is to set your ISO to 100 and your aperture to f 5.6 for a one hour exposure. Experiment to see what works best for you.
To get a photograph where the stars aren’t streaking across the image, the most important component is a mount to hold the camera and track the stars as they rise in the east and set in the west. With one axis pointing toward the celestial pole, one of these equatorial mounts will act like a one-handed, 24-hour clock. In one day (actually 23 hour and 56 minutes) it would make a complete circle as the Earth rotates.
The down side is that equatorial mounts that are suitable for astrophotography can be quite expensive. They can never be big enough, stable enough or have smooth enough motors.
This month
The summer solstice was Saturday, so the nights now are as short as they will be all year. Mars and Saturn are still good evening targets. If you are out at dusk you can still see Jupiter near the western horizon before it sets. The summer Milky Way, rising just after dark is the richest field of stars you can see all year. Spend some time scanning it with binoculars and you will be rewarded by seeing numerous star clusters and even a few glowing emission nebulae.
hakes_c@fortlewis.edu. Charles Hakes is an assistant professor in the physics and engineering department at Fort Lewis College and is director of the Fort Lewis Observatory.
Useful links
Astronomy picture of the day: http://antwrp.gsfc.nasa.gov/apod/astropix.html
Old Fort Lewis Observatory: www.fortlewis.edu/observatory
Four Corners Stargazers: http://groups.google.com/group/Four-Corners-Stargazers
