Magic of Glass - Part 3

The Magic of Glass
Part 3

In the Last part of the series, we looked at Refractor telescopes. In this part we put the spotlight on the Reflector Telescope. In most people’s opinion, the Reflector telescope is nothing less than a boon to modern amateur Astronomy; I would list two main reasons of why reflectors sometimes score over refractors in the field of Amateur Astronomy.

Let’s look at the history of reflector telescopes.
As we all have made note of from previous parts, Galileo was the first person to look at the heavens with a telescope of his own handiwork, we have all seen telescope evolve from that period, although it should not surprise the reader that the idea, that someone could use mirrors instead of lenses was probably older than the invention of the telescope, but after the invention of the telescope, the idea of replacing the lens with the mirror, slowly but steadily started to brew in the intelligentsia of the  scientific community, more so with those closely related with Astronomy. The answer eluded most, for long, people tried various experiments with mirrors and the results were mostly unsatisfactory, until it was the great Isaac Newton, the father of Physics and the inventor of the Calculus who came to their rescue with the World’s first completely working model of the Reflecting telescope.


It is to him, that we credit the construction of the Reflecting Telescope, and rightly christen the design as the “Newtonian Reflector”( Although in terms of scientific accuracy, it is duly noted that he did not come up with the idea on his own, but brought into existence a instrument  no doubt, though persistent efforts and gave the world a gift, one of the many he has given. Why he was interested and what prompted him to build this contraption is a story for another time). The design of the Newtonian was so simple yet so elegant that it was a overnight success. Suddenly mirrors could be used instead of expensive lenses and the size of the telescopes could grow, in turn gathering more light than ever before, gone were the days of the small handheld telescopes using lenses, it is probably right to say that the Astronomers of the time were gripped with “aperture fever” (A feeling common among amateurs who have grown out of their relatively small telescope and want a larger telescope to see more of the heavens).

The Magic of Glass - Part - 2

The Magic of Glass
Part 2

In this part of the series, we take a look at the different types of telescopes readily and cheaply available (mind you, cheap is only a relative term) in the market today.

  • Note- Focal length is nothing but the distance that from the lens to the convergence point.
  • The F-ratio of the telescopes is calculated as the focal length of the lens divided by aperture of the lens (the size of the objective lens or mirror in your telescope).
  • F.O.V(Field of View) is quite simply how much area you are seeing at any point

The Focal length and the F/ratio play a vital role in the use of a telescope, it is very important you know what they mean.

The F-ratio varies in classification from “fast” to “slow”, a fast f/ratio means the image will be brighter and will give a wide field of view, the Fast f/ratio’s up to f/6 provide great wide field views. Faint nebulas and Star Clusters which are spread across a large area are much better rendered, but there is one shortcoming, the magnification is not the greatest, if you have other viewing interests, the telescopes with f-ratios of f/10 and above are best for planetary viewing and looking at binary stars. The Telescopes between f/6 and f/10 are a middle route that most tend to take if you are not really interested in the details of it all. Many hobbyists keep multiple telescopes for this very reason.

The Eyepieces

The eyepiece can be called the heart of the telescope, for without the eyepiece, the Telescope is quite useless. Having mentioned that, you need to know what type to buy and which one, there are plenty of options. The first thing to remember about the Eyepiece is, the lower the focal length of the Eyepiece, the higher the magnification you are going to achieve. The Magnification can be very simply calculated, simply divide the focal length of the telescope by the focal length of the eyepiece. For example, if the Focal Length of the Telescope is 1500mm and the focal length of the eyepiece is 25mm, the magnification will be 1500 / 25 = 60x, but I have to disappoint you at this point by saying the earlier statement does not mean that if you use a 1 mm eyepiece with a telescope of focal length 1500mm, you will get 1500x of magnification. There is a limit on every telescope called the magnification threshold; it is roughly 60 x per inch of aperture. For example, I use a 6 inch Schmidt-Cassegrain Telescope, the Magnification threshold of my telescope is 6 x 60 = 360x. This means for all practical purposes, I cannot “bump up” the Magnification beyond 360 x and get a good, clean image.

focal lenght

The Magic of Glass - Part 1

The Magic of Glass
Part - 1

All people who adore science have at some point looked up at the stars and wondered if the heavens could ever be brought to earth. People, from time immemorial have always thought of doing something like this, observing the heavens. In this series, we shall look at the different kind of telescopes and where to get them. Let’s focus on the Technology in the first part of the series.

The telescope was invented by a Dutch spectacle maker, Hans Lippershey (it is still unclear as to who the inventor of the telescope is, since there are many other contenders for the title but most reliable sources point to him.), it’s a common mistake to credit the invention of the telescope to Galileo, although he was the first person ever to observe the heavens, with a telescope, he did not invent it. The first application of the telescope was not the heavens as most had expected, however it was in the battlefield to observe enemy troop movements. As soon as Galileo heard the news, he was fascinated, and decided to fashion a telescope, for himself .The one he crafted was, by our standards” quite shabby”. It was no where near the precision that we have achieved today with our technology and advances in optics.

hans lippershey

Hans Lippershey

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