STARS AND NIGHT SKYAfrican Stars
  
Clear skies, the absence of pollution, and the deepest of dark nights make Southern Africa excellent for Astronomy and Stargazing and there is only one place to go: Southern Africa.

Clear skies that provide open windows to witness the heavens: to see stars in patterns that signify mapped constellations, and to view deep sky objects (hundreds of thousands of objects have been discovered that lie beyond our solar system and are known collectively as deep sky objects; this term encompasses clusters of stars, nebulae and the galaxies).If you should see with your mind as much as with your eyes: the astronomical vastness of space is for the broad-minded.

There are a total of 88 official constellations, 82 of which can be seen fully or partially from Southern Africa; only 6 of the identified constellations are true northern hemispheric constellations. Our observable constellations range from the smallest (Crux, the Southern Cross) to the largest (Hydra, the Water Snake), including one of the most recognizable, namely Orion, The Hunter. As for deep sky objects, more than 45 are visible in the course of an evening, year-round. Among the cited top 100 deep sky objects, we have: 40 open star clusters (e.g. the stunning Jewel Box in Crux, and the magnificent Pleiades, commonly known as the Seven Sisters, in Taurus), 24 globular clusters (e.g. Omega Centauri, the largest and brightest globular cluster we know of), 15 galaxies (e.g. Andromeda, a spiral galaxy some 2.5million light-years away), 8 planetary nebulae, 7 bright nebulae, 5 dark nebulae and 1 star cloud. Many of these are visible to the unaided eye, and are even more spectacular witnessed through binoculars and telescopes; and with Sutherland’s SALT Observatory building the largest single telescope in the southern hemisphere over the next few years, with a hexagonal mirror array 11metres across, SALT will be able to record distant stars, galaxies and quasars a billion times too faint to see with the unaided eye – as faint as a candle flame at the distance of the moon...In fact, the most famous astrophotography photos of the Milky Way and the Southern Cross were done from South Africa.
 
Galaxy
A component of our universe made up of gas and a large number (usually more than a million) of stars held together by gravity. When capitalized, Galaxy refers to our own Milky Way Galaxy.

Satellite
A body that revolves around a larger body. For example, the moon is a satellite of the earth.

Stars Star
A large ball of gas that creates and emits its own radiation.

Star cluster
A bunch of stars (ranging in number from a few to hundreds of thousands) which are bound to each other by their mutual gravitational attraction

Solar flares
Violent eruptions of gas on the Sun's surface

Revolution
The movement of one celestial body which is in orbit around another. It is often measured as the "orbital period."

Rotation
The spin of a celestial body on its own axis. In high energy astronomy, this is often measured as the "spin period."

Red giant
A star that has low surface temperature and a diameter that is large relative to the Sun.

Light year
A unit of length used in astronomy which equals the distance light travels in a year. At the rate of 300,000 kilometers per second (671 million miles per hour), 1 light-year is equivalent to 9.46053 x 1012 km, 5,880,000,000,000 miles

Orbit
The path of an object that is moving around a second object or point.
We can only see a few thousand stars at most with our unaided eyes. These are a mixture of stars which are nearby, and bright stars which are further away; but they are only a tiny fraction of the 100,000,000,000 stars in our own galaxy. We can't see stars in other galaxies without powerful telescopes. In fact the entire brightest neighboring galaxy (The Andromeda galaxy), which contains more stars than our own, is only as bright as an average star visible to the unaided eye.

Planets

Moon The planets are often conspicuous and will usually draw a question from somebody, along the lines of "What's that bright one over there?" So... check in advance and identify which planets are going to be up, and where they will be.

No one will notice Mercury, so you will need to actively hunt it down and point it out. It is a tricky one and needs to be at or near its greatest separation from the sun. You need to catch it at the right time of twilight -- too early and the sky is too bright to see it, too late and it's lost to the horizon. My experience is that there is a window of about 10 to 20 minutes in which Mercury can be seen -- but it is a worthwhile pursuit. Finding and catching Mercury can be an adventure in itself.

Mercury, Venus, and Mars make their best impression, from a stargazing point of view, by eye -- the telescope does not add a great deal unless you are quite serious about your astronomy. However, if Jupiter or Saturn, or both, are visible then either will make a good showing in the telescope -- Saturn for its rings and Jupiter for its bands and for its moons.

Hence if you expect to have Jupiter in the sky it is also worthwhile to do a little homework and determine where the moons will be positioned. This varies hour by hour so you need to be precise about when you will be showing it. We once had a moon pop out of nowhere while we were watching -- Io was emerging from behind Jupiter (very cool).

Magazines such as Astronomy or Sky & Telescope will give you planet positions, as well as positions of Jupiter's moons (Sky & Telescope also shows Saturn's moons). You can also get software that will give you this information. A good web-based Java program is available at Sky View Cafe and an excellent, full listing of available software can be found at nineplanets.org. Personally I use The Sky astronomy software.


Pointers

The luminous beauty of the night sky has a presence that is overwhelming, and commands the attention of your tour group. This spectacular display does all the work -- our added value to the tour group is when we reveal to their eyes the things they otherwise would not have seen, noticed or appreciated. So stargazing is show and tell, with emphasis on the "show" and less on the "tell". These tours are designed to support that approach. Some pointers:

I have found that deep sky objects that are not visible (or barely visible) to the naked eye and pop out in the binoculars are a particular delight. A couple of classic examples are the Coathanger in the summer sky and the Beehive in the Winter/Spring sky. Some other similar goodies are the Double Cluster (winter), the Double-Double (summer), M13 (summer), and the Andromeda galaxy (fall/winter).

Focus only on what is easily visible. Extremely faint and challenging objects are best left for later, when you are testing the limits of your telescope with the hard-core crowd. Galaxies, in particular, look spectacular in photographs and fall well short of those images in the telescope. Aside from the Andromeda galaxy and M81, galaxies require a crystal-clear, dark sky, or a big telescope (8 inches or larger), and preferably both.

Attach a story to each celestial feature you point out. Answer the question of why your friends care that they can see it.

Hit the high points quickly and early, because the night chill and fatigue of the day will get to the crowd. Even under the best circumstances you will gradually lose more and more of your budding astronomers as the evening wears on.

If you are going to use a telescope for any part of your tour, it's best to have someone help by finding the next target in the telescope for you while you are showing and explaining other items of interest.

If you are going to direct stargazing and point the telescope too, practice finding those objects until you can do it quickly & easily. Practice on your own, well beforehand. Optimally you will practice on several nights under different conditions. If you're used to your light-polluted back yard and you get out under a dark sky full of stars you hadn't been seeing before, that can present a time-consuming challenge that will test the patience of your tour group (not a good tour feature).

You don't need to cover everything. Most stargazing sessions I lead with Scouts or otherwise, are spur-of-the-moment affairs prompted by the abrupt realization that we are under a perfect, clear, dark sky. As a result, while we have covered all the items of all these tours at one time or another, I doubt I've ever conducted a stargazing tour where I hit every single solitary item on the list. Rather, I follow the general flow and outline of the tours and allow the discussion to follow the interests of the group. As you might imagine, that seems to work out best.


Recommended Equipment

Reference Guides

The single best book to have is the Audubon Society Field Guide to the Night Sky. I have over 40 books on astronomy and I find I keep going back to this one. Plus it fits in your back pocket.

Also handy is Orion DeepMap 600 which can be found at www.oriontel.com.

Note that you want these for preparation in advance. If you plan on referencing them while you're stargazing, bring along a red LED flashlight, which will prevent you from destroying your night vision once your eyes are dark-adapted.

Flashlight

You don't want this for seeing so much as you want it for pointing out stars and tracing out constellations. You therefore want one with a highly focused beam that will give you a searchlight shaft into the night sky. (If you can afford a green laser pointer - I can't, they're a hundred bucks - these are much cooler and more high-tech than a flashlight.)

Binoculars

The single most versatile instrument for astronomy is a pair of 10x50 binoculars. They're small and light so they can go on any outing, and they're powerful. In fact, a little too powerful -- at 10x magnification you need to control the shaking from your hands to get the full resolving power of the image. (Some people prefer 7x50 or 8x50 for this reason.) Laying on your back, bracing the binoculars with your hands against your face, works really well for steadying out the shaking. You can also get a tripod mount for most binoculars.

Decent ones (Meade, Celestron, Orion, Bushnell) will go for around $50, excellent ones will go for as much as ten times that (or more of course). Avoid the cheap ones (think of how much you can see through those magnifying glasses from cereal boxes).

Telescope

Only if you really think you need it. For stargazing purposes you won't use it extensively, although it can add a nice touch. Decent ones start at around $150, and the prices for good ones quickly skyrocket from there -- from $400 to $1000 for a nice and reasonably mobile instrument. The diameter of the objective lens, which is the most important dimension of a telescope, needs to be greater than 3 inches for the telescope to do much good.

The telescope I use is a Meade ETX (the original, with a 3.5" objective). For more challenging targets (and more impressive telescope images) we rely on one of the dads who occasionally brings along an 10-inch scope.

The tours are just fine without a telescope at all. I include the telescope objects in case you have access to one and you really want to use it. If you don't use it, no one will miss it. In fact, even though I usually have binoculars handy for stargazing (and personally I really like them), I have found that the tours are just fine with no optical aids at all. We're stargazing, here, after all.