A telescope is an instrument used to observe objects from afar. The word is derived from Greek words tele and skopein which means “far” and “to see” respectively. Contrary to popular belief, it was not ‘invented' by Galileo. There has been evidence of a refracting telescope that has been in use in the Netherlands during 1608 and its development was credited to spectacle makers Hans Lippershey and Zacharias Janssen, and a third person Jacob Metius. However, it was Galileo who improved on the devices soon after so they can be used for exploring the heavens.

A telescope works by collecting electromagnetic radiation, which on earth-speak means visible light. However, with the development of space technology, there has risen the capability to utilize the full range of the electromagnetic spectrum and use the radio band. The first radio telescope was used in 1937 and there have been subsequent development of telescopes that can work with other wavelengths such as gamma rays.

Photo by: Mike Peel Creative Commons

A telescope has A telescope has three major capabilities – the ability to magnify, the ability to resolve images and create sharp images and the most important being the ability to collect light so it ‘sees' better (which is also the reason why your pupils enlarge when the room is dark or when it's nighttime). The part of a telescope which collects light is the ‘objective'. The objective of a refractor telescope is a glass lens and a reflector telescope uses a (surprise, surprise) mirror.

The first telescopes used to observe the heavens where refractor telescopes and they were subject to problems of chromic aberration or color distortion and spherical aberration among others. It wasn't until 1668 that the first practical reflecting telescope was developed by no other than Sir Isaac Newton with the idea that parabolic mirrors can reduce aberration and more than a hundred years after, achromatic lenses where developed and the rest, as they say, is history.

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Setting circles are disks used on various telescopes outfitted with an equatorial mount to aid in the
search for astronomical objects anywhere in the sky by referencing equatorial coordinates used in the star charts. It functions by attaching those graduated disks to the right ascension and to the declination axis within the equatorial mount. The disk positioned on the right ascension will be graduated by time, through hours, and even minutes and seconds.

A declination disk on the other hand is graduated into degrees, and then minutes and seconds. Locating any object on the celestial sphere through setting circles is just similar to searches on a terrestrial map using the longitude and latitude values. Some variations on the right ascension circle provide a northern hemisphere scale and southern hemisphere scale.

Today’s applications of setting circles play an important role in astronomy. Research telescopes benefit much from the large diameters of these disks. When combined with a vernier scale, any telescope can be greatly enhanced with its arc minute accuracy.

Portable telescopes are very useful especially with amateur astronomy. And when equipped with such disks, the setup will normally require polar alignment, which is the alignment related either to the northern celestial pole or to that of the southern celestial pole. Setting the right ascension disk after polar alignment is also required. Observers make use of a calculator or any known star in the sky to synchronize the right ascension disk with the sidereal time.

All these functions make setting circles an important component when searching the sky for anything.

Using a Telescope with Setting Circles

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These illuminated reticles are actually needed to accurately align telescopes. It also has a grid of patterns placed in the eyepiece of an optical instrument and is also used to establish a scale or position. A reticle control would allow manual rotation of the reticle for use when it comes to lunar surface alignments. Crossing by the line on the star image defines a plane containing the star. Crossing of the other line defines another plane containing the same star or a different one.

The intersection of these planes forms a line that defines a direction of the star. To define the internal orientation of the particular star being viewed, sightings on at least two stars are required. Each star sighting requires the same procedure. Multiple reticle crossings and their corresponding marks can be made on either or both stars to improve the accuracy of the sightings. Upon completion of the second star sighting, the guide computer would then calculate its orientation with respect to a predefined reference coordinate system.

Centering stars without a reticle would be very difficult. It would be best to select the best reticle for your telescope to make sure that finding the stars and centering it would be easier.

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However, if you were to view the same image through one that has got better resolving power, you would be able to see the details clearer. How is the resolving power measured? This is measured by the absolute smallest angle that can be resolved.

Did you know that there are some really powerful modern telescopes that are capable of counting the number of lines in President Roosevelt’s hair that was placed upon a dime located 3.7 kilometers away? For astronomers, it is all about getting the best telescopes with the greatest resolving power as this means that they would be able to view celestial objects better. This is also one of the reasons as to why radio telescopes are far bigger than their optical counterparts.

A good way of increasing resolution is to make an interferometer which is basically connecting telescopes together. The image would have the same sharpness as one that was taken by a single instrument which would extend from one end of this interferometer to another.

So there you have it, a few bits and bobs with regards to gauging a telescope’s resolving power.

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The first convex lenses to be used in refracting telescopes were designed and made by a Dutch optician named Hans Lippershey in 1608. What he discovered about how looking through a concave and convex lens positioned in front of each other can make distant objects look very much nearer paved the way for the use of these lenses in telescopes. Just a year later, the first refracting telescope to be used in the study of space was made by Galileo Galilee. It was through this device that he was able to map the surface of the moon and to discover four of the moons circling Jupiter.

But how exactly does a seemingly simple device enable you to peer into outer space? Well for starters, refracting telescopes basically have two parts that function to gather and collect light – the objective lens and the eyepiece. The objective focuses the light by bending it into a focal point. This focal point is where the image is formed. Once the person looks into the eyepiece, a concave lens will gather and focus more light than the eye could so that a magnified image can be seen.

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This pertains to a device for detecting and analyzing radio waves emitted from astronomical objects. You commonly see the radio telescope as a large dish. The first of the long line of radio telescopes was built by the engineer Karl Guthe Jansky who was able to capture static radio signals from the galaxy’s core. Today, the largest radio telescope the Arecibo Observatory, which is 305 meters in diameter, is found in Puerto Rico. Radio telescopes are large in order to capture sharp radio images from radio wavelengths extending from one millimeter to as long as one kilometer.

A radio telescope is basically composed of an antenna (the large dish you usually see), a detector, and amplifier. Incoming radio waves are captured and focused by the antenna toward a supersensitive receiver capable of detecting signals as weak as 10-17. Some of the parts of the telescope are kept at an absolute zero temperature for sustained maximum performance. Because of the range of frequencies of radio waves, radio telescopes specifically the antenna can differ in terms of configuration, size, and design. Unlike optical telescopes, which are almost always in mountains, radio telescopes are built in valleys to be screened from electromagnetic interference.

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In a reflecting telescope, it either uses a single or a pair of curved mirrors to reflect light in order to form an image based on the location where the said telescope is focused on. Basically, a telescope has three parts, namely the eyepiece, the objective, tube and mount assembly, and the counterweight. The primary mirror is the formal name of the objective. It is the telescope’s essential part, since this is where light is refracted or gathered to produce the image or view based on the area of focus.

The shape of a certain telescope’s mirrors or objectives is that of a sphere or of parabolic disks. It is made of polished reflective metal that is known as speculum metal up until the 19th century. Nowadays, this part of usually made up of glass or another material with a mix of reflective substance or layer coated. The only down side is that the size of a primary mirror must be adequate enough to sustain its own weight, as well as to prevent from deforming due to gravity.

One known example of this is the famed Newton’s Telescope of 1668, whose objective is made of a 3.3 inch polished metal. Another type of telescope that made a huge breakthrough for objectives is the Crossley Reflector, whose primary mirror was made of silver on glass, in replacement of metal. The latest known change in objectives was made on the 200-inch Hale Telescope, wherein the said objective is made of aluminum on metal.

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When someone mentions astronomy, what often comes to mind are planets and stars seen through a telescope. Astronomy is indeed the study of heavenly bodies, but it need not be with the use of telescopes and sophisticated instruments. Astronomy can also be studied using just the naked eye, and this was how the early pioneers of this science investigated the heavens and learned much about the stars, planets and galaxies. They used the naked eye, and their brilliant minds, to make sense of the movements, orbits and characteristics of the celestial bodies. Many of these bodies were in fact discovered using the naked eye alone, without telescopes.

Here are some astronomical bodies and events that can be studied using the naked eye:
• The planets – Mercury, Venus, Mars, Jupiter and Saturn are visible to the naked eye, as long as the person knows where to look in the sky. The outer planets normally cannot be seen without a telescope.
• Meteor showers – Shooting stars and meteor showers have long fascinated stargazers, and watching them on the night sky is an activity enjoyed by many.
• Sun rise and sun set – Staring directly at the sun, with or without a telescope, is not advisable because it can damage the eyes. The times of the sun’s rising and setting are important daily events that influence human activity.
• Moon rise, moon set, and the lunar phases – These are also closely monitored events that influence human activity. Many people still use the lunar calendar based on the phases of the moon.
• Stars and constellations – The brightest and biggest stars, and the constellations they are a part of, can be easily seen on a clear night sky. A star map is useful in identifying them.
• Galaxies – Our own galaxy, the Milky Way, can be seen using the naked eye. Distant galaxies are likewise visible as dim cloud clusters beyond the stars.

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Not only does astronomy cover different branches of science, it also borrows concepts in fiber optics as well. Objective (optics) is also taken into account when it comes to science, or in this case, astronomy.

Objective (optics) means the optical part of a scientific instrument such as a telescope or microscope, that is responsible for gathering light from the observed specimen and makes sure that these light rays are then focused at different levels to produce the real image.

In space studies, Objective (optics) is the optical part of the telescope. It is the lens located at the end of the refractor or simply put, is the front end of the telescope, where people usually set and focus at a fixed point in the sky or at a long distance. This is not to be confused with the other end of the telescope, where people usually take a look on the area being fixed upon. The light gathering capability and the maximum distance it can take is dictated by the diameter or size of the lens. This means that the bigger the objective lens a certain telescope has, it means that the dimmer the object it is focused on and more details can be shown or seen.

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After all, this telescope is known to provide an immense view of the sky itself. What is a Rich Field Telescope (RFT)? They are actually low power telescopes with immense field of view. They offer some of the advantages of the binoculars where large areas of the sky may be scanned through them.

There are viewing techniques that will take in a large area of the heavens. These are very useful because some celestial objects will not fit into a narrow field. Also, many large galaxies have a very low surface brightness. It means the area is large and dim, therefore they can only be seen when surrounded by dark sky. Large deep objects are easily observed when there is some contrast between them and their surroundings. Only a wide field of view will provide that contrast.

To take advantage of a true rich field telescope you must have a small compact scope. These can be hand held or mounted. They are very portable and easy to use. This should provide you with views of the Milky Way that are truly breathtaking. This is something that you and your family would certainly enjoy doing.

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