Focal Length of Convex Lenses

Physics Project Finding the focal length of a convex lens Turn your speakers on! Music: I Wish by Trentemoeller (Late Night Mix) www.karilyn.wetpaint.com

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Backyard Astronomy - Gazing Into The Past

Astronomy continues to be one of the more popular hobbies. One of the major reasons is because you can stargaze just about anywhere. Although country settings away from city lights are best, everyone can see the moon. And even though the closest star (after our sun), Alpha Centauri is over 4 light years away, can be seen easily with the naked eye.

While simple stargazing with the naked eye is great fun, using a telescope can be awe inspiring. The view of the heavens through even a small telescope is something that has to be experienced to be appreciated. Even though modern technology allows us to view the celestial realm with images on tv and through the internet, there is nothing quite like seeing it though a telescope.

Different Telescopes

There are basically three kinds of telescope. The refractor and reflector and catadioptric. The refractor telescope collects and bends light with a convex lense and eyepiece. This bending or refracting concentrates the light rays to a small focal point making things appear larger or brighter. The reflector telescope on the other hand, as its name suggests, reflects light from a convex mirror in the back of the telescope to another mirror in the front and finally to the eyepiece. The convex shape of the mirrors "scoop up" and concentrate the light to a focal point thereby magnifying an object. Caution: Objects in a telescope appear closer than they really are!

The third type, called Catadioptric, combines features from both reflecting and refracting telescopes.

Which one is best? For image quality and portability, my choice is the catadioptric. It's easily transported and has the best features of both the reflector and refractor telescopes. Because of the design, catadioptric telescopes are almost completely free of the coma found in reflectors and the chromatic aberration in refractors. Chromatic aberration is the distortion of color due to a lenses inability to bring various colors in the light into focus. Coma is the distortion of an object at the edge of your field of view.

Convenience is another factor to consider. If you have to transport your telescope as I do you'll appreciate the catadioptric's compact size, light weight and how easy it is to set up and take down.

Travel Through Time

We all know light travels at an unimaginable speed of 186,000 miles per second. Even our sun's light takes about 8 minutes to reach us once it's left the surface. Now think about our closest neighbor, Alpha Centauri. It's over 4 light years away so the light from its' surface began its' journey over 4 years ago. We are actually seeing it as it was more than 4 years in the past. In a very real sense we are looking back in time. Think back to what you were doing 4 years ago. Whatever it was, while you were doing it, light eminated from the surface of Alpha Centauri and came screaming along at 186,000 miles per second on the long journey toward earth, arriving here just a few minutes ago. Alpha Centauri is actually part of a star system. 3 separate stars, Alpha Centauri A and B form a binary while Alpha Centauri C is 13,000 Astronomical Units (AU) away. This is part of the reason it's easily seen with the naked eye, you are actually looking at 3 stars instead of 1.

Closer To Home

One need not look outside our own solar system to find amazing sites in the night sky. The moon may look smooth when seen with the naked eye but train a telescope on it and prepared to be wowed. The level of detail will depend on your telescope but the craters and jagged mountains are clearly visible. The best viewing, in my opinion is when the moon is in a crescent stage as the shadow created by the earth allows for much more detail to be seen. I saw the moon for the first time through a telescope years ago. I watched as it slowly drifted past my field of view and could almost feel its' movement. Of course I knew it moved along its' orbit around the earth but to actually see it moving was an incredible experience.

Saturn, probably the most fun to observe because of the rings, makes for spectacular stargazing. Depending on the time of year, the rings of Saturn are visible and to this observer, quite breathtaking. While I couldn't discern any colors or variations in the rings, they appear quite distinctly from the planet itself, something I'd seen only in books prior to that.

Stand on the shores of any ocean on earth and get a sense of the sheer enormity of it. Then realize that it's not even a drop in a bucket by comparison to the size of the sky it sits beneath. Looking up at the stars at night makes you realize just how massive everything really is. There is no number that can truly measure or even estimate its' size or dimensions. The only thing that can even remotely compare to the wonder of space is the imagination of those who view it.

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Wearing Contact Lenses the Right Way

Although the use of contact lenses to correct eye problems has now become quite common, these are still a few common queries associated with the correct use of contact lenses shared by both those who use lenses for the first time, and those who have been using them for some time.

There are a few basic steps you must keep in mind while handling or using your contact lens, in order to keep them from getting damaged, and also for optimum comfort on your part.

One commonly asked question is whether or not it's possible to tell if the contact lens is inside out. There's a very simple way to do this, first place the lens on your finger so that an upturned cup is formed. Then bring the lens up to eye level so that you can see the rim of the convex surface clearly. If the top edges of the lens appear flared out, the lens in inside out, and if it just forms a cup, or a 'U' shape, you're holding the lens correctly.

Tinted lenses appear to have darker edges when held right side up, and some lenses have the brand name of the manufacturer etched onto the surface, which also assists in telling if the lens is inside out. However, there is no risk involved in applying the lens to your eye, inside out, you will only feel a slight discomfort.

Another important factor in using contact lenses is lens maintenance. Make sure you wash your hands thoroughly before applying the lens to your eye, or when removing it. However, it's best to avoid soaps that are oily or too scented, since these tend to contain substances that might interfere with the make-up of your lens, or end up damaging it.

Take special care to avoid using products containing lanolin.

The steps involved in cleansing and applying contact lenses are as follows: first, gently shake your lens case containing the contact lens immersed in storage solution, to loosen the contact lens should it be stuck. Avoid touching or pulling the lens with your fingers as much as possible since you might end up damaging it. Then place the lens on your palm and rinse thoroughly with the cleansing solution prescribed for your specific brand.

After cleaning out the lens, dry your hands and place the lens on the tip of your finger, use your other hand to hold the eye open, and gently put the lens in place. Roll your eyes, and blink in order to let the lens settle. If you experience any discomfort, chances are that the lens hasn't been positioned properly, in which case it has to be removed, rinsed and replaced properly. If you are stand in front of a sink while removing or applying a lens, cover the drain with a clean paper towel, since if you drop the lens into the drain by accident, it'll be irretrievable.

By adhering to a few simple rules of contact lens usage, you can obtain the best results from this extremely convenient device.

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