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Newbie Telescopes, Books
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Blob's guide to buying a telescope

Not all telescopes are suitable for astronomical use. Try to avoid the very cheap variety. Remember that this initial financial outlay is all you ever need to spend.

There are two main types of astronomical telescopes; a refractor and a reflector.
In a refractor, the light from a star is collected by a lens (object glass) and brought to focus. Here a second lens, known as the eyepiece magnifies the image. In a reflector, the light is collected by a specially shaped mirror and reflected back up the tube. Then the light is brought to focus and, as before, magnified by an eyepiece. This is the Newtonian form of reflector; there are other variants.

Refracting telescopes
With a refractor try to go for a large aperture - that is to say, the diameter of the (front) object glass, which is the light collector. The eyepiece does all the actual magnification. The bigger the aperture the greater is the amount of light is available to the eyepiece, and a high magnification can be used.

The maximum useful power for magnification is X50 per inch of aperture. That is to say, if you have a 3-inch refractor (object-glass 3 inches in diameter), you can use a power of 3x50=150. So the object will be enlarged 150 times as compared with the naked-eye view. You can, in theory, use a higher magnification - say x300 - but the image will be so faint that it will be quite useless. So avoid any advertised telescope that states magnification only.

Reflecting telescopes
With a reflector of the Newtonian types, the aperture is the diameter of the mirror. The rule of thumb is x80 per inch of aperture. Inch for inch the reflector is less efficient (because light from the target objects has to undergo several reflections, and over time the silver coating degrades). Remember that eventually you need to culminate the mirrors! This is not for the faint hearted... A cheap reflector will use a spherical mirror; a quality reflector will have a parabolic shaped mirror. There are various other patterns that use both mirrors and lenses, and these can be excellent. But, unfortunately, they are very expensive.

If you want to buy a telescope, don't pay a large sum for a refractor with an object-glass of 60-mm diameter, or a Newtonian reflector with a 4.5-inch mirror.

Small telescopes do not gather enough light to be really useful astronomically. The prices are, fortunately, quite cheap. The following gives a guide as to what to expect to pay for a suitably mounted telescope: 60mm refractor on an altazimuth mount from 100 (cheap scope, eg. Celestron Firstscope 60AZ)

3 inch refractor on an altazimuth mount from 199.98 (SkyWatcher Evostar 90 f/900 AZ3 )
3 inch refractor on an equatorial mount from 209.00 (SkyWatcher Evostar 90 f/900 EQ2 )
4.5 inch reflector on an equatorial mount from 149.00 (Celestron Firstscope 114 EQ )
6 inch reflector on an equatorial mount from 399.00 (Orion Europa 150)
8.75 inch reflector on an equatorial mount from 699.00 (Orion Europa 250 )


An altazimuth is a simple mounting, on which a telescope can be moved freely in any direction. An equatorial is more complicated, and means that only one motion is necessary (east/west). For astronomical photography, an equatorial is more or less essential.

It's full of stars
For observations of stars, aperture is again the essential factor; the more light you can collect, the fainter objects you can see. Consider, for example, the moons. With the naked eye, you can see the large mare, and a few large craters. Any telescope will show hundreds more.

I am not suggesting that a very small telescope is quite useless. Of course it isn't. What I am saying is that in my opinion, it is not satisfactory for anything but the most casual observation. Rather than spend a large sum of money (100) on a very small telescope it is, I feel, much better to buy a good pair of binoculars.

Binoculars
They are defined by the apertures of the object-glasses (in mm) and the magnifications. Thus a 7x50 pair means a magnification of 7, with each object-glass 50mm in diameter. In general, I would recommend a power of between x7 and x10. With a higher magnification the binoculars become too shaky to handhold, and a mounting is necessary. The following gives a guide as to what to expect to pay:

9x63 Mini Giant Binoculars
Moderate, 9x magnification allows a wide 5.0 field and 7mm exit pupil. Extra-long 26mm eye relief. Good hand-holdability. Weighs 2 lbs. 10 oz. The lenses and BAK-4 prisms are fully-multi-coated and the aluminium barrels internally glare-threaded to eliminate internal reflections. Each features pop-down eyeguards and rubber armouring for a secure grip. Includes hard case, deluxe wide neck strap, and lens caps. Five-year limited warranty.


7x50 binoculars from 49 the best for young persons
8x30 binoculars from 30 lightweight, and can view the moons of Jupiter
10x50 binoculars from 49 ideal for the older person
12x60 binoculars from 200 Nice.. not recommended for beginner.
20x80 binoculars from 450 Heavy and expensive, needs a tripod stand, which costs about 50

Telescopes versus binoculars
Both have advantages and disadvantages. For a total beginner a pair of binoculars are recommended, and later on, he/she can purchase a small scope. A pair of binoculars takes no time to 'set-up'.

Of course never look directly at the Sun (or reflection) with any telescope or binoculars, even if you use a dark filter. This will almost certainly damage your eyesight. Have a look at these `before and after` pictures below, to see the affect...

Buying second-hand
What about second-hand telescopes? I would tend to recommend the refractors here...Remember that the silvering on the mirror, in a reflecting scope, only has a limited life expectancy.

So, watch out! A bad telescope does not always betray itself at first sight, and this applies to new telescopes as well as second-hand ones. A simple test on a bright star will easily show up the faults; the star should be point like and crisp. Try to get skilled advice if possible.

Making your own
You can, of course, decide to make a telescope yourself. Lens making and mirror making is probably best left to the professional. The cost of a ready made 6-inch mirror, for example, is about 100. The mounting is purely a problem of mechanics, but it is essential to know just what you intend to do before setting out.

Whatever you intend to do, I wish you luck, and clear skies.


-- Edited by Blobrana on Wednesday 4th of November 2009 08:46:17 AM

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Selecting a Christmas telescope

Christmas is coming! If you are considering getting a telescope for the family astronomer, you are probably about to go shopping, and worrying about making the right choice. You want to open new horizons, not acquire another cupboard dust gatherer. There are some traps out there. I hope these notes help a little in avoiding problems.
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When you ask most amateur astronomers (or me) which telescope we recommend for beginners, we will all tell you what you don't want to hear: don't buy a telescope first. Buy a pair of binoculars, learn the sky, and then buy a telescope. But that isn't the answer you wanted, so you go buy a telescope anyway. I understand. I've been you. So, if you aren't going to listen to me: here is my advice on what telescope to buy as a first telescope.
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Cheap Telescopes
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Buy Cheap Telescope

Having a hard time trying to buy cheap telescope? You dont know what kind of telescope would you buy? How much will you pay? And where is the perfect place to buy cheaper but excellent telescope? Then just go on reading. This might help you clear your mind.
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Ed ~ much cheapness

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RE: Newbie Telescopes, Books
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OpticsPlanet Named as One of America's Top Online Retailers
OpticsPlanet, Inc., the largest specialised retailer of sport optics, tactical and military gear, binoculars, microscopes, telescopes, rifle scopes, and sunglasses, announced today that for the third consecutive year it has been ranked among the top 500 retail websites based on annual sales.

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Title: THE DAY WE FOUND THE UNIVERSE
Author: Marcia Bartusiak

Famous astronomy anecdote: It's 1923, and astronomer Harlow Shapley, the leading proponent of the theory that the Milky Way is the one and only galaxy, gets a letter from Edwin Hubble. Shapley reads it, turns to a colleague and says, "Here is the letter that has destroyed my universe." Marcia Bartusiak's new book is the backstory of that anecdote.

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Space may be the final frontier, but for several years, exquisite fragments of it have been lovingly captured on film by Professor Greg Parker - from his back garden in Brockenhurst.
Now the best of those breath-taking sights have been published in a 155-page book: Star Vistas, a collection of the finest wide-field, deep-sky images taken by Professor Parker, many of which have been published in the Daily Echo.

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Those of you who have astronomy as a hobby will find it very captivating. If you have a telescope, not only can you be a part of science, but you can have some fun as well.

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The magnification of telescope is calculated by focal length divided by lens size. Just look at your eyepiece and there will be a marking of number written on the side like 6mm or 20 mm. Consult your manual for the focal length.

Magnification = Focal length / size of eyepiece

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-- Edited by Blobrana at 23:42, 2009-02-07

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