Comets PanSTARRS and ISON are racing toward Earth and will potentially provide stunning shows for the inhabitants of the planet in spring and late autumn this year. Although the paths and behavior of comets is difficult to predict, comet PANSTARRS, coming in the spring, is currently forecast to be about four times brighter than 1997′s Hale/Bopp comet. And in November and December, Comet ISON should treat observers to a comet over 2000x brighter than 1997′s celestial treat.
Although slim, there exists the possibility that ISON could put on the most spectacular cometary show since 1965, if not become the greatest comet since 1680. As photography aficionados, many of us will want nothing more than to record what could be a once-in a century, if not once-in-a civilization type of event. But, there are many questions about how to photograph comets PanSTARRS and ISON, especially with digital cameras. After all, digital camera technology for consumer use was in its infancy at the time. In this article, we will concentrate on how to take digital photographs of these comets.
As far as equipment goes, you will be well-served to have a DSLR camera, which allow you to change lenses. What focal length of lens to use depends entirely on the size and brightness of the comet at the time you go out, as well as what sort of picture(s) you are looking to achieve. Most people will be tempted to use a telephoto lens, or a lens with a long fixed focal length. These can be just the tool you are looking for if the comet is small and bright, or to photograph the bright head (coma) of the comet. However, if want to photograph the entire comet, particularly with a landscape as a backdrop, you will be better-off using a lens with a very short focal length.
Before the comets get here, try practicing with your camera, taking photographs of various objects in the night sky. Some of the brightest stars will be about as bright as PanSTARRS should become at its brightest, so take lots of photographs of the brightest stars you can see to get used to what your camera will do under these conditions. Since you will (hopefully!) be getting to a dark area in order to take your photographs of the comets of 2013, take your test photos under those same dark skies.
Comet ISON could be about as bright as a quarter-Moon on November 29th, so your natural test subject here will be a quarter Moon! Comet ISON will also be visible low on the western horizon just after sunset. So, go out just as the quarter Moon is rising, early in the evening or after midnight, and photograph our celestial neighbor while it is low in the sky.
While testing, you should do everything the same way you will do it to photograph comet ISON and PanSTARRS. First, set your camera up on a tripod. If it is a windy night, make sure your tripod is stable, digging the feet part-way into the ground if necessary.
Advanced cameras not only allow you to change your exposure times, but your f/stop as well. You should open the aperture of your lens up as far as it will go (or nearly so) for nearly any photography of the night sky. A lens with a wider opening lets in more light, which is all-important. Of course shoot in the RAW format to get the most of out of your photos.
As a good rule of thumb, with a wide-open lens, a bright star (like Sirius) should photograph well with exposure times around ten seconds. This will likely be around your best exposure time for PanSTARRS at its brightest, around the middle of March. The Moon, just two or three days away from full, is often best-exposed at times around 1/30 of a second, while a full Moon is best with exposure times around 1/125 of a second! So, most of your quarter-Moon experiments should be a fraction of a second.
Comet PanSTARRS should start to become visible to the naked eye around Valentine’s Day, and will quickly brighten for a month. Around the middle of February, set your camera on a tripod and open the aperture up all the way, trying exposures in the 10-30 second range. This will be long enough to bring out a lot of detail in the comet that you cannot see with just your eyes, without blurriness from the rotation of the Earth.
It is important to experiment ahead of time using real celestial bodies as your practice subjects. Also, remember that different types of exposures will give different results. So, when you head out in March to photograph Comet PanSTARRS and in November and December for Comet ISON, take a lot of photos at a lot of different settings. You may be surprised what you turn out!
Learn more about the comets of 2013 from James Maynard
Special thanks to Daniel Fischer of Cosmos4U for his assistance on this article