Telescopes ??? Principle of operation and factors that affect its properties

Telescopes are devices that are used to view the distant objects. They find its use in astronomy and physics. It enables you to view the distant objects by magnifying them. There are many types of telescopes and their prices vary according to the specifications. Many accessories are also available that can be used in conjunction with the telescopes. Small telescopes that are used as toys are also capable of viewing some objects around 50 meters away.

Principle in which the telescope works

The principle in which the telescope works is very simple. There are two lenses that make up the task of viewing the objects that are at a distance. One of the lenses picks up the light from the object viewed and makes it available at a focus point. Another lens picks up the bright light from the focus point and spreads it out to your retina so that you can view. The lens that picks up the light from the object is called the objective lens or primary mirror. The lens that picks up the light from the focal point is called the eyepiece lens.

Factors that affect the viewing of the object

The capability of the telescope to collect the light from the object that is viewed and the capability to enlarge the image are the factors that affect the efficiency of the telescope. The capability to collect light from the object depends on the diameter of the lens or mirror, which is otherwise called the aperture. The larger the aperture the more the light it can collect. Enlarging of an image depends on the combination of the lenses that are used. The eyepiece in the telescope performs the magnification.

Some of the world's largest optical telescopes in operation

We say a telescope to be larger based on the aperture size. Based on this we can say that Keck and Keck II are the largest telescopes in operation with an aperture of 10 meters diameter. The Keck telescope is composed of 36 mirror segments. This is located at Mauna Kea, Hawaii. The next largest is Hobby-Eberly located at Mt. Fowlkes, Texas which has an aperture of 9.2 meters. You can get a list of the largest optical telescopes at http://astro.nineplanets.org/bigeyes.html.

Choosing your telescope

The choice of the telescope largely depends on what you want to observe. You can choose compound telescopes and refractor type of telescope for viewing through the urban skies. For the rural skies, you can use compound telescopes and reflectors. They are better than the refractors type of telescopes. Each type has its own advantages and disadvantages. Hence, many people have different telescope for different purposes.

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You Might Be An Ultralight Backpacker If...Steve GillmanIf you you find yourself saying "Hey, that's a good idea," to more than one of the following, you might be an ultralight backpacker. They are collected from various lightweight backpacking forums. For those of you that don't share our passion for ultralight backpacking, let me explain that these are funny, but also mostly true stories.

You Just Might Be An Ultralight Backpacker If...

- Your wife's purse holds more stuff than your backpack.

- You pack light for a family trip to Grandma's house.

- You use the fruit scales in Walmart to determine the weight of a possible new piece of gear.

- At home you use just 4 toilet paper squares, to "practice".

- You read that last one and say, "toilet paper?"

- You have no idea what the title, scale or contour interval of your map is because.... you cut away all of the margins to save weight.

- You sleep at home with the temps turned down while in the buff just to get used to the cold so you can take an even lighter sleeping bag.

- The thought of 1000 fill-power down gives you a little shiver down your spine.

- You're glad you're going bald.

- You're wondering if your compass would still work OK without all that heavy liquid.

- Your woman says, "Go down baby!" and you hop out of bed hootin and hollarin and order a Western Mountaineering Highlite!

- You no longer have tags on any clothing you wear.

- Your mailman is trying to figure out why people send you empty boxes all the time.

- You eat with $40 titanium chopsticks instead of a plastic fork because they weigh .01 ounces less.

- You walk through the grocery store thinking "saltines have 1760 calories per pound, but mixed nuts have 2720 calories per pound".

- Your waterproof/breathable rain jacket cost more than your best suit.

- You shave ALL the hair off your body to save a few ounces on your "from the skin out" weight!

- Your trail runners weigh more than your multi day pack.

- You know the weight of your backpack, and not your wife.

- You have to take your tent down to use your combination spork/toothbrush because you used it as a stake.

- You compulsively weigh things you have absolutely NO intention of ever taking backpacking, just because.

- You take laxatives before a trip, just to "lighten the load."

A Note To Backpackers: You might be an ultralight backpacker if you can easily come up with more of these from your own experience.

About the author:
Steve Gillman is a long-time backpacker, and advocate of lightweight backpacking. More of "You Might Be An Ultralight Backpacker," plus advice and stories can be found at