General

In addition to visual planetary observation and recording of observations by drawing, the amateur astronomer may also wish to record observations by photography. Until fairly recently, planetary photography involved the use of conventional photographic film exclusively as the recording medium but with the advent of video photography (videography) and the availability of charge coupled devices (CCD), astronomical photography in general has undergone a revolution. The principles of each of the types of planetary photography will be described here.

The planetary photographer's camera

The best kind of camera to use for planetary photography is any one of the many makes of 35 millimetre single lens reflex (SLR) type, the majority of which will be found suitable for this kind of work. Whatever make of SLR you choose, it should have the following features:

1. Removable lens.

2. It should have a ‘bulb’ or ‘time’ exposure.

3. The focusing screen should be as clear as possible to facilitate critical focusing.

4. There must be a suitable socket or other provision for attaching a cable release.

5. The shutter should operate quietly and smoothly with minimal vibration of the mirror.

Small and moderate-sized high-quality telescopes reveal an astonishing amount of detail on planetary discs but when attempts are made to capture the detail on photographic film the result is usually disappointing. Something always seems to be lost as compared with what can be seen by direct visual observation.

The planets can be among the most exciting things to see with a small telescope; they can also be among the most disappointing. The excitement is natural: these are other worlds we're seeing, places we've heard about all our lives, places that have the familiarity of an old friend even the first time we find them in our telescope. But that's the key to the potential disappointment. We already know in our imaginations what we think they should look like. We've seen the photographs that spacecraft have been sending to us since the early 1960s. Somehow, the little dot of light in our telescope isn't quite the same.

The first thing to be aware of is that planets are bright but small. This means that they tend to be very easy to find, once you know where to look, but rather disappointing at first to look at. Because they're bright, they can stand the highest power magnification that the sky conditions and your telescope will allow. Because they're small, you'll want all that magnification. Be patient; wait for calm nights (often those with thin high clouds) and for those special fleeting moment of steadiest seeing.

(Uranus and Neptune are faint and small! They're tiny greenish disks of light; that's why “planetary nebulae”, which look much the same, got that name. Pluto is exceedingly faint, only fourteenth magnitude, and it is utterly undistinctive.

Getting Oriented: The Moon is rich and complex in a small telescope; under high power, you can get lost in a jumble of craters and all the mare regions seem to meld together. So the first thing to do is to get oriented.

The round edge of the Moon is called the limb. The Moon always keeps almost exactly the same side facing towards the Earth. Its apparent wobbles (called “librations”) are small; craters near the limb always stay near the limb.

The Moon goes through phases, as different sides take turns being illuminated by the Sun. The whole sequence takes about 29 days, the origin of our concept of “month”. This means that, except for Full Moon, the round disk we see will always have one part in sunlight, one part in shadow. The boundary between the sunlit part and the shadow part is called the terminator.

The terminator marks the edge of between day and night on the Moon. An astronaut standing on the terminator would see the Sun rising over the lunar horizon (if the Moon is waxing; or setting, if it's waning).