Monday, April 12, 2010

What Can I See with My Telescope: Saturn

Saturn is one of the things in the sky that you can see through a small telescope that is just as impressive as it looks in the photos you see. While many deep sky objects, such as nebulas and galaxies, do not look as impressive as in the books and magazines, Saturn does.

Not only that, there is something special about the way it looks that makes it look different than any photograph or video. When you see it with your eye, it's special. Just like the Grand Canyon, it has to be experienced to be appreciated.

Amateur astrophoto of Saturn by Rochus Hess
Astrophoto of Saturn by amateur Rochus Hess

As I write this, Saturn is a bright star visible in the early evening sky. To find out whether it's visible as you read this, visit one of the free on-line star charts, such as those listed to the right.

What to expect with:

7x35 to 8x65 Binoculars: A bright object that looks somewhat different from a star. It will be steadier than most stars, and a pale yellow in color under most skies. You will also be able to see 2-3 small companions as points of light. One will be brighter than the others. These are satellites of Saturn, the brightest is Titan. Saturn itself will not show a disk with small binoculars, but sometimes it will look misshapen as a result of the rings.

60 to 90mm Telescope: At 50 to 100 powers of magnification, you will have a nice view of Saturn and the area around it. You will probably see 1 to 3 satellites, the brightest of which will be Titan. The rings will be easy to see. At 150 to 200 powers, look for the shadow of the rings on the surface of the planet, under good conditions it will appear as a thin black line. Careful looking with a relaxed eye should show the bands in the atmosphere of Saturn. Some bands will be yellow, others will be white. They will go from side to side across Saturn.

4.5 to 6 inch Telescope: Far more detail will be visible at powers of 150 to 200 times magnification than with a 60-90mm telescope, in most cases. Also, more moons will be visible, as many as five under the best conditions. From brightest to dimmest they will be Titan, Iapetus, Rhea, Dione, and Tethys. Tethys is a difficult find with a 6" scope. Titan will almost always be the brightest when it is seen. Iapetus, Rhea, and Dione are hard to tell apart. There's a Saturn Satellite Finder on Sky and Telescope's site, since you can't tell your moons without a program.

Saturn itself can show a lot of detail. The best way to see it is to stay at moderate magnifications for this scope size (150-200 powers) and look with a relaxed eye. Give yourself time, be seated if possible, and use a scope that tracks the sky with a clock drive or computer if possible. See if you can see the bands within the light bands of Saturn's atmosphere. Enjoy the rings, the break in the rings called the Cassini Division should be obvious with good optics.

7" to 9" Telescope: At this point it's possible for Saturn's features to be washed out by how much light your telescope collects. However, telescopes in this range are excellent for observing Saturn. Start at low powers (50 to 100x) and observe Saturn and its neighborhood, looking for up to 9 moons (see the section on 4.5-6" scopes). Then move up to moderate magnification, about 150 t0 200 powers. At this point you may need to actually block off some of Saturn's light to see fine detail. There are many ways of doing this. My favorite simple methods are to either partially block the light coming in to the telescope with my hand, or do the "hat trick" by blocking some of the light with my hat.

By moving the object you are using to block either more or less light, a little at a time, details can come out for you that would not either without some of the light blocked, or using a light blocker that sits still.

With this size of scope, you can take magnification up to 300 powers or more. Most scopes will give the best views at 350x or less, some can go up to 450x before the image degrades. As the magnification goes higher, the problem of too much light will be less of a problem. However, at higher magnifications you'll need to have some means of tracking the sky, or you won't be able to see much of Saturn before needing to move the scope to follow it across the sky.

Larger Telescopes:

Larger scopes can be used in the same way as 8" telescopes. The only advantage to larger scopes is that they can see more detail within the detail, and can pick more detail out of the rings of Saturn. They are more sensitive to washed-out images of Saturn than scopes in the 7-8" size, but when properly "masked off" they can provide sharp, stunning views. Fine detail that larger scopes can pick up includes "clouds" in the atmosphere of Saturn, streaks in the atmosphere, more detail at the edges of the different bands in the atmosphere, such as swirls, and of course the dimmer inner rings of Saturn. Very well designed scopes of smaller size can pick out these details under excellent viewing conditions, but with a larger scope it's easier to do under less than optimum conditions.

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