Last month, I talked about astrophotography on the cheap. You can take photos with wide fields of view and either very short or very long exposures to get your feet wet in the hobby.
If you are fortunate enough to have a sturdy mount available that can follow the stars, then you can easily use your same digital camera to take pictures that are far more spectacular than anything possible less than a generation ago, and even better than many of those early Astronomy Pictures of the Day. (Browse the archive of photos from the mid-1990s in the attached link to see this.)
To get higher quality photos, the most important process, not really a trick, involves noise removal. Noise is anything in your image that you didn’t intend to be there. Just like listening to very soft music while there is background noise in the room, you want to be able to get rid of the background so you can hear the music more easily.
In pictures of the night sky, the biggest source of noise is from the camera itself and will be unique to each digital camera. In broad daylight, you would never consider taking a picture with the lens cap on, but at night, half of your pictures will be taken exactly that way. With the lens cap on, the only thing recorded in one of these “dark frames” is the internal noise of the digital camera.
Because of the random nature of this camera noise, you should take several, for example 10, dark frames and average them together. You can then subtract this dark image containing only the noise from the “light frame” image that has both the signal (what you are taking a picture of) plus the unwanted noise. The subtraction is most successful when the light frames and darks frames are exactly the same exposure length and same camera temperature. To further improve your final product, take many pictures of the same target and average them together.
Many software packages can accomplish this, and other, useful astrophotography processing techniques. DeepSkyStacker is one such free program I have used with some success.
Monsoon season has entrenched itself in the Four Corners. Even if we aren’t getting much rain, we often have late afternoon and early evening cloud cover. However, after midnight, the skies are often clear and freshly washed of the summer haze. This might be a time to go to bed extra early and wake up while it is still dark.
The morning of Aug. 13 is the time to catch the peak of the Perseid meteor shower. Unfortunately, this is only a few days after the full moon, so that could wash out your view of some of the dimmer meteors.
Just before sunrise on the morning of Aug. 18, Venus and Jupiter, the two brightest things in the sky besides the sun and the moon will be exceptionally close to each other. Also near those planets that morning is the “Beehive” open cluster M44. This set will definitely be worth the early alarm clock.
[email protected] Charles Hakes is an assistant professor in the physics and engineering department at Fort Lewis College and is director of the Fort Lewis Observatory.