One of the most watched telescopes on eBay is a TINY 76mm Newtonian
DO NOT WASTE YOUR MONEY ON TINY OPTICAL RUBBISH
Tiny little telescopes will not show you anything useful... They will disappoint every time!
Do yourself a favour and invest twenty or so minutes of your time reading this guide to avoid
regretting your first telescope purchase for life!
You can get an instrument capable of giving years of good astronomical views for around a week's wages... Read on!
There are plenty of eBay and YouTube guides about buying telescopes and they will ALL point you away from Newtonian reflectors under 120mm diameter - And quite rightly! Please read on!
I REVIEW or UPDATE THIS GUIDE REGULARLY
Updated - November 2018
First published by me 2010.
There is a very good reason that so many disgruntled people are selling their tiny telescopes on eBay...
...It's because tiny telescopes are no good for astronomy!
The two types of telescope I am going to recommend are: 'Newtonian Reflector'
and 'Astronomical Refractor'. I will generally refer to them as Newtonian and Refractor, to save confusion between reflector and refractor.)
The reason I recommend only these two types is that these are the two best suited to the beginner because they are the simplest and therefore have the largest aperture for your money available - So you can get into the right SIZE of telescope with the minimum outlay.
Above: My Phenix 127mm (5") f10 Astronomical Refractor - A very nice bit of kit.
Recommended Newtonian Above: My 150mm (6") f5 Newtonian Reflector - If these 6"ers are too expensive and you really can't manage - A 130mm parabolic Newtonian will have to suffice! New <£300 (Nov 2018)
Resolution in the image and 'light gathering power' is dependent on the diameter of the mirror or lens. If you can't resolve the detail then
NO AMOUNT of
magnification will show it!
You NEED the BIGGEST objective you can manage (either financially or physically - telescopes get heavy!) to allow detail to be shown no matter the magnification used!
Some telescope companies state things like, 'Collects 250 times as much light as the human eye,' in their adverts. This sounds like a gimmick, but actually it's a very good point. Light gathering power is dependent on aperture minus any obstruction.
If you like to think in terms of multiples of the human eye that's fine. (which is pretty standard at 7mm diameter = 38.5mm squared, fully dilated).
Just be aware that the eye is a funny thing and twice the light doesn't look twice as bright!
If you use more magnification than the telescope can show detail then this is 'empty magnification'. See magnification section later for more on this.
Go Compare: Comparing the refractor views close up! (View in 50mm on the left, 80mm on the right in this comparison). (Actually Left side
Saturn image is a little bit too detailed!)
Left: Approx view of Saturn with 50mm (2.0") refractor or a 80mm (3") Newtonian.
Right: Approx view of Saturn with 80mm (3.1") refractor or a 150mm (6") Newtonian. (I'm happy with this image representing a really still night!)
There are two main considerations: Splitting binaries (Close pairs of stars cannot
be split with tiny telescopes or higher magnifications) and the visible star magnitude limit. A larger telescope will always show closer pairs as individual stars and show fainter stars than a
smaller telescope will.
Left: See the Difference: Left is a 20x view of the Pleiades (M45) with a 6" 150mm telescope (Lower frame). On the upper frame is the same cluster with a 50mm. Note not only the many more stars in the larger telescope, but the splitting of the double star just below centre.
Not just two stars but four are visible in the larger telescope.
Resolution: The triple star shown resolves itself through use of larger telescopes - Not bigger magnifications.
< Have a Look!: This video demonstrates the effect of widening the aperture from 50mm to 150mm and back.
Deep Sky Objects
Left: Orion Nebula: The nebula M42 in Orion. Once again the central star is not split with a tiny telescope but shows itself to be a 'Trapezium' of four stars in the bigger 'scope. Also note the amount of nebulosity that can be glimpsed in the bigger telescope (R).
See diagram, Left. The
stars shown are just a connected blob, at any magnification, for any telescope under 140mm / 70mm.
You get to choose which view you would prefer by picking a telescope of the size I
advocate in this guide!
Authentic View Left: Mars at a favourable opposition (Close to Earth). You'll need to look closely - But observe the differences in detail between the three telescopes. Once again you can choose which view you would like by buying the size that gives the view you want!
A reflector transmits only about 85% of the light that enters the system, a refractor something like 98%.
(This does not apply to refractors)
Small Newtonian reflectors often have spherical figured mirrors. The mirror's shape is incredibly accurate and MUST be parabolic to bring all the rays of light to the same focus.
Manufacturers of small telescopes don't bother with this final 'figuring' of the mirror. It's time consuming and needs special testing of the optics.
Left: See the fuzzy stars on the spherical image.
They leave it out because it's an expense they can avoid - Their telescopes, however, are sub-standard as a result and give awful image quality. They try to get around this fault by supplying long focal lengths (f9 - f12) because the difference between the spherical and parabolic mirror is smaller (But still significant!).
If you want to get the best out of your telescope, and use the optimum magnification and have the best images you need to have a telescope with a parabolic mirror. That usually means at least a 130mm Newtonian.
Ray Diagram: The parabolic mirror gives much sharper point images (The detail on the planets will also be smudged by a Spherical
mirror). The spherical mirror produces out of focus blurry stars and smudged planetary images.
The parabolic mirror brings all the rays of light to a focus at A. Whereas, the spherical mirror brings light from the centre of the mirror to a focus at A, whilst it brings the light from the edge to a focus at B. Providing some focussed light and some slightly out of focus light at all points between A and B. There is no clear focus with a spherical mirror.
Yet another reason to get a larger telescope than these toys of 100 - 115 - 120mm diameter!
Something I must tell you: I was asked this question by someone who had read this guide.
My answer is simple: “There are no such things as novice needs!”
See for Yourself:
Right Pic. - Aperture does, even at lower magnifications!
The benefit of an equatorial mounting is that you only need to move the telescope about the polar axis to follow a star as it moves across the night sky. The polar axis points to the pole star, approximately, and therefore the polar axis needs to be set to the observer's latitude.
They can be a bit of a mystery for the uninitiated, but basically you point the polar axis at Polaris then move the other two axes to find and follow your object. (The other guide explains in detail)
If you want to learn to be an amateur astronomer and know about the night sky this is not the way to go!
There is a Go-To version of the Equatorial, which is useful once you have learnt your way about the sky.
The Alt-Az Go-To is also not suitable for astro-photography as the field rotates as you track an object smudging the detail.
When amateur astronomers like myself say "BIG", we have a better understanding than eBay sellers who have never seen a telescope over 2"... (Even power sellers - Don't make the mistake of thinking that people who sell lots of things necessarily know much about the things they are selling!)
Astro-Buddies: Me (L) and best astro-friend, Paul, with his 14" Newtonian - Another nice bit of kit! The Eagle-eyed of you may notice that it is on a 'Dobson' type mounting - Yes, it is, but it's NOT a Dobsonian telescope! The main mirror is 70mm thick and it's in a nine-point suspension cell - Not very kitchen sink design! (Courtesy Astrospace)
You may notice the obvious difference between the two telescopes I'm advocating. Their size!
The objects seen in the larger telescope are visible because of the larger optics only - It really is nothing to do with magnification.
Magnification is not the be-all-and-end-all of telescopes! You can see a surprising amount with relatively modest magnifications - If you were to pin me down and say I could only have ONE eyepiece (therefore one magnification) I would choose one which gave about 150x magnification. Not 200x or 300x or even the fantastic 525x magnification - Just 150x*.
Useful magnifications vary with the size of the telescope.
I used the 30" (750mm) Newtonian at the Amateur Astronomy Centre Nr. Bacup. And, once again, we had some lovely views of Jupiter, at 200x magnification. (See Pic. below.)
So, to make my point: Even 'huge' telescopes utilise 'reasonable and usable' magnifications.
Eg2. Focal length 1250mm / Eyepiece 8mm = 156x magnification.
Following this statement above it can be seen, and I hope I'm not getting too mathematical, that the maximum magnification you should use on a 60mm refractor on a normal seeing night would be 112x and on a 76mm Newtonian, just 76x. (On a NORMAL night you can use up to half your maximum magnification remember!) Anything higher than this is 'Empty Magnification' and shows you nothing more!
Refractor of 80mm or Newtonian of 150mm - The magic sizes I recommend!
(See, I haven't just plucked these sizes out of thin air :o)
In 1977, my parents bought me a 60mm diameter refractor for Christmas - I thought I knew better than the books I'd read and I'd pestered for this particular telescope... It had an Alt-Azimuth mount, no finder and four set magnifications: 15x 30x 45x 60x... And with that telescope I learnt, very quickly, that you can see a few things, but not enough!
Left: My Astral Telescope: £55 A week's wages in 1977.
Since that enlightening Xmas, and through the last forty years of observational astronomy with some brilliant telescopes, I have been of the opinion that it is a good idea to start off in astronomy with a telescope that will show you more than the very basics. (Does it show?)
Yes, a tiny telescope will show you A FEW things, but why bother with this first step?
When I started off in this hobby you could only get these two types, Refractor & Newtonian Reflector (Nevertheless, they are still the best for starting out) - There were no Maksutovs, no Schmidt-Cassegrains, no Catadioptrics, and even a simple 6" Newtonian was £400 bought new! The only option was to buy a telescope we could afford - a 60mm Refractor on a useless AltAz tripod for £55.
Nowadays, there is a wealth of different kinds, and the prices have come down massively. So - why would you suffer the tiny telescopes when decent sized telescopes are available for you at very reasonable prices?
YOU CAN NOW GET YOURSELF A VERY GOOD TELESCOPE FOR A WEEKS WAGES!
You're looking for a Refractor 80mm and larger... Or a Newtonian 150mm and larger...
Look out for fantastic bargains on eBay.
Second hand is as good as new with most astronomical instruments as they very rarely sustain damage. Just make sure that the seller will sell for the low price these instruments attract (Why they don't use a reserve price I don't know!)
Left: This 100mm Helios Refractor sold on eBay for £100 - WOW!
TINY: Even these won't
These two telescopes look very impressive with their EQ mountings and slow motion knobs... and they're appealingly cheap!
But don't be fooled - They won't show you all the sights you're expecting.
I get quite a few messages asking what else you should buy to get started in astronomy when you get your new telescope.
The most useful thing you can get is a good star atlas. I recommend two publications. Peter Lancaster Brown's excellent introduction to visual observing 'Star and Planet Spotting' (Available
second hand on eBay from 60p) and for those who have some experience Wil Tirion's 'Sky-Atlas 2000.0' which shows stars down to magnitude 8 (A real must for those with telescopes above 150mm)
Which you can pick up for rather a lot more (Mine was £30 when I got it in 1981).
Left: My two superb reference works.
Left: My SkyAtlas
2000.0 is an invaluable tool for finding anything you need to see.
A superbly detailed star atlas it shows stars down to magnitude 8.
It has 26 maps of the night sky with colour-coding.
The Orion area of the winter sky shown left. (Note Orion Nebula Enlarged at left showing magnitude 10 stars).
Left: My copy of Star & Planet
Spotting is invaluable as an observer's reference. It gives lots of useful information on the Constellations, Observing the Planets, Variables,
Comets and Meteors. There are also basic and very usable star chart pages in the middle. They show stars down to magnitude 6.
The winter sky, including Orion, shown left.
I would recommend that every amateur astronomer should have a copy!
It is also
very useful to use a computer based program such as 'Stellarium' (invaluable Free download). There are many different ones but for now why not try a free one?
This will, after a bit of playing about with the options, equate you with the way the sky moves. You can set specific times or view the sky as it presently is. Move forward or backwards, in time, at varying speeds. You can zoom in, use a telescope or have a whole sky view! You can get information on any object. You can look at how the planets move and work out where and when to see specific things. You can turn various useful things on and off: ecliptic, planet orbits, EQ grid, Alt-Az grid, labels, ground, atmosphere, daylight, clock, constellation lines and art!
< Laptop View: Screen-shot 'Stellarium'. Orion area again with Betelgeuse selected, view South with atmosphere, daylight and ground selected. Equatorial grid is on. Constellation lines are off.
It's easy to set your location so you can see the exact sky where you are, and easy to change it so you can see the sky for where you will be going on holiday for instance! Lets you see the Southern sky or work out which stars are visible from various latitudes. It's a lovely program visually, and is worth a look. It will never replace the star atlas for usefulness 'at the telescope' - But it is invaluable for seeing how things work and planning your observing sessions.
It is always handy to have a pair of binoculars. They really are almost a must to accompany your telescope. Almost any size will do, except the tiny sports types. Binoculars are 'sized' by their magnification and their diameter. For example, a pair of 10 x 50 binoculars give a good view. They magnify 10x and have lenses 50mm across and are referred to as "Ten by Fifty" (not 'Ten times Fifty'). Personally, I have a pair of 8 x 40 binoculars. They have a slightly wider field of view (Because of the lower magnification) and are lighter and easier to hold steady (Because they are smaller).
Binoculars will help you find the exact position of the bright galaxies, check quickly on the position of Jupiter's moons (Oh, yes, don't let the claim that a telescope will show Jupiter's moons be a selling point – If it wasn't for the proximity of the very bright Jupiter you could see them without a telescope!) With your binoculars you can see and the planets out as far as Neptune, and they give many wide views of the milky way. They are useful tracking down the Messier objects too. I would recommend you get a pair of 8 x 40, 7 x 50, or 10 x 50 binoculars.
Above: Bino-Bargains: My excellent Swift 10x50s are superb and were got second hand for £19
My I.R.Vision 8 x 40 wide angle view binoculars are not ideal for astronomy but were better than nothing for a tenner!
Try to keep things simple - No huge magnifications, No Zoom Eyepieces and make sure you check the size - Lots of misleading sizes advertised on eBay!
Whilst the 60mm and 70mm and even 80mm binoculars are very nice for astronomy, you do need a tripod and mounting to hold them steady. The main object of using them in conjunction with your telescope is for conveniently looking at something before observing. It's not very convenient if you have to use a tripod! By all means get a large pair for use with a tripod if you like the views - But this would be an instrument in its own right and not really used for a quick check prior to observation with the telescope.
For your telescope:
Buy nothing extra for your telescope until you are familiar with using the telescope you bought. It's very easy
to spend lots of money on things that you don't or won't need. Take your time to get used to your instrument and your view through it. After a while you will realise what you
The next thing you'll probably want is another eyepiece to extend the range, sometimes higher magnification and sometimes lower.
It can be beneficial to get a 2x Barlow lens. This device effectively (optically) doubles the focal length of your telescope and therefore all your eyepieces can be used as they are or in unison with the Barlow to give twice the magnification. Sometimes useful but not always - Remember the magnification limit of your telescope and try not to exceed it. Try not to duplicate magnifications (Waste of money) if you buy a 10mm it will give you a magnification. Adding your Barlow will give you another magnification twice that of the first. If you then bought a 20mm eyepiece adding the Barlow would duplicate the magnification you get without it using the 10mm. Always take care you won't duplicate.
Barlow also means that if you have a refractor of f10 you will be using it as though it is an f20 with the resultant shrinking of the apparent field of view and 'photographic slowing of the
system'... Care is needed and I wouldn't spend a lot on a Barlow unless you can try it first!
Another important part of the telescope is the 'Finder Scope'. This is the smaller telescope attached to the side of the main scope that allows you to locate things in the eyepiece. You can adjust the finder's cross-hairs to precisely line up with the centre of the field of view of the main scope, even at high magnifications. It can be tricky, but you can't really do any harm. Lining up the finder should be done with a distant earthbound object in the daytime so time can be taken to get it spot on. The more accurate the finder is set up the easier observations will be in the dark.
Some finders that are supplied with telescopes are woefully small for the telescope they serve. A finder of at least 25mm is recommended and 30mm or 50mm is much more desirable for 150mm or 200mm reflectors.
Eg: If you're hoping to line your telescope up on Neptune, you have to bear in mind that the planet is magnitude seven or eight and to find it easily in the finder, the finder has to gather a good deal of light too! (The 70mm Refractor I review later in this guide had a finder of just 15mm diameter - Couldn't see much of anything fainter than Jupiter!)
The finder needs to gather light and show stars that cannot be seen by the unaided eye. Some scopes come with something called a red-dot finder. This should be replaced with a light gathering magnifying finder to enable you to see things that your eye can't. What use would a red-dot finder be in locating Neptune when it is Magnitude 8 and your eye can only possibly see to magnitude 6? You need a proper finder...
Left: Red Dot finder types in common supply.
These won't show you anything you can't see with your eye!
Left: A Proper Finder scope - 6 x 30mm
This will show objects down to magnitude 8 or 9. You can line up better because of the magnification and cross-hairs.
Do not pay any extra money out for a 'Moon Filter' - No self respecting amateur astronomer would use such a gimmick (You cannot harm your eye with the moon's light!).
It can be bright but if you're looking at the Moon then there's no need for dark adaptation - Astronomers spend most of their time trying to maximise the amount of light available to the eye - Why would you darken the image?
Each time light passes through a lens or filter there is some loss of light and there is some degradation of the image. Leave it out and see more of what's there!
As you learn more about the things you're looking at you'll get an idea of the direction you would like to go and decide what your favourite types of astronomical object are.
At that point you will know what you need to get next to improve your viewing of your particular area of interest.
Different areas of astronomy require different equipment. You've read about needing a big Newtonian for Deep Sky objects, and the planets are best seen through a large refractor. These are the kinds of considerations you will learn to apply to your future optical equipment planning.
Also, as you read more, talk to people and learn about astronomy, you'll come across other types of telescope. Some of these are very well suited to specialisms. In particular and worth a mention here is the Maksutov catadioptric telescope. Absolute wonder on the planets! However, I would still not recommend a beginner to start here - Get some experience with the simpler telescope types before overcomplicating it for yourself!
You may find that your telescope is a bit big for just grabbing quickly to have a look at something, or it
won't fit in your car with all the family when you're off to the seaside but you'd like a telescope in case you need to observe something. You could do worse than get yourself a 'Travel Scope'.
This is an easily portable telescope designed for use on the go.
A travel scope should not be considered for your Main telescope, but will complement your Main telescope. There are plenty of short focus refractors in decent sizes that will still show you plenty when you're out an about. For instance I have an astronomy acquaintance who takes his in a back-pack when walking his dogs and sets up while they have a run about on the beach.
You can get a very good 70mm Travel Scope for around £50 new (Including the carry-bag).
The 70mm objective lens gives enough detail for casual observing and the f6 ratio gives a wide field and bright deep sky images too. A good all rounder of a decent size. (Please resist buying anything smaller than this even as a second telescope!)
You may have to buy a short focal length eyepiece (4mm) or 2x Barlow or even a 3x Barlow to get decent planetary image size (100x Magnification and above) as some come only with 20x and 40x magnifications which, while refreshingly conservative, are nowhere near enough to show detail on the planets.
Celestron Travel Scope on extending tripod with carry-bag. Ideal for 'Astronomy On-The-Go' but should not be your main instrument, unless as a 'stepping stone'.
be had for around £50 new!
The travel scope should not be considered as a starter scope if you are interested only in the planets as the image is too small. These scopes are excellent for having a good look round the wonders of the universe and getting a feel for what can be seen with a 'proper' instrument (But will let you down on planetary views).
Resist buying the reflecting types of travel scope at all costs! They are far too delicate for true travel scoping! Refractors are much sturdier.
If you have limited funds and want to get into astronomy with a useful instrument, this is a great way. By getting started with a 70mm Travel Scope you are able to spend very little and have a scope that will be of use, even if you do 'take the plunge' and buy a larger telescope in the future - It's always a good idea to have a small, easily used telescope handy!
This telescope is great for most aspects of astronomy 'on the go' and having a quick look around the night sky, but, once again, I wouldn't recommend it for your main telescope, although I must admit that it would have been much better than my first 60mm instrument! (You know why... Think about it... That's right, it's a BIGGER diameter lens!)
Being able to 'see' with your telescope is something that is helped by the size of your telescope, but also needs a lot of experience. Start off with the magnifications I have suggested and keep observing. As you get used to seeing objects in a telescope you'll learn to really 'see' the detail that's th
It might sound like I'm trying to put you off but actually I'm hoping that you'll
realise that what I'm saying is, if you're initially disappointed with your telescopic view of the heavens, stick with it and you will gradually be able to see more and more.
Someone like me, who has spent years looking through telescopic equipment, can see a whole lot more than a raw beginner and somewhat more than someone with a year's experience. But this is a fantastic hobby and there wouldn't be much fun if everything was there on a plate for you straight off!
Most of the fun of this hobby is gradually learning more and more about the universe and learning to see it for yourself.
I think a quick word about Dobsonian telescopes is in order. Having had John Dobson as a house guest when I lived in Horncastle, when he gave a lecture at the Horncastle Astronomy Weekend, I think I am able to provide you with informed information on this variation on the Newtonian telescope.The original design was for a large aperture telescope, using the Newtonian layout.
The mounting is a simple altitude and azimuth non-equatorial design (ie. up and down left and right).
The beauty of these telescopes was that the mirror could be made from much thinner, cheaper glass than the standard Newtonian because it was on an Alt-Az mounting and not an equatorial. The mirror was supported on bubble-wrap, cardboard float points and a 'sling' type support strap! The complicated mirror cell and thick glass mirror of the equatorially mounted Newtonian was avoided and much bigger telescopes became affordable to amateurs.
Left: John Dobson and Paul Money at the HAW: Paul's 14" Newtonian on the 'Dobsonian Mounting' can be seen behind them. (Courtesy Astrospace)
Although these telescopes are fantastic to use, in the hands of someone with little experience tracking the object is tricky and high magnifications are impractical. Consequently, planetary observation is difficult for the beginner. I would respectfully suggest that the Dobson / Dobsonian telescope should be avoided until you get some experience with the easier to use 'equatorial mounting'.
If you see a 'Dobsonian' telescope advertised make sure it's not just a Newtonian on a Dobson mounting, or worse, they're calling it a
Dobsonian because it's on an Alt-Az mounting of simple design! ... To be a true Dobsonian telescope it has to have the thin main mirror supported on the sling type support and it should be
Call me pedantic, but they're selling you an Alt-Az Newtonian and telling you it's something special... NO.
The whole point John was trying to get across wasn't 'ease of use', if that was the point they would be mounted on equatorials! They were designed to be telescopes of huge diameter built at home on a shoestring! Mass producing Dobsonians seems to be missing the point entirely.
Anything that isn't huge*, and cheap to boot, isn't really a Dobsonian at all, but a Newtonian 'dressing down' to snare the unwary!
Don't pay megabux for a Dob! (*By huge I mean 12" 300mm and over.)
There are a number of companies now selling Catadioptric Newtonians. I would suggest that these are to be avoided by the beginner.
They have optically extended focal lengths - So you'll find a short tube but with a focal length of typically 1400mm. (The telescope will look on the outside like the telescope shown above (a 750mm f5), but may state 1400mm f10). The view in these telescopes is narrow and unless the mirror is very good the image quality will suffer.
There are two types: The better designed ones use an optical 'corrector plate' which is a thin lens at the tube aperture and are 'sealed systems' (See picture below) - Others use a Barlow lens in the focuser and are not closed optical systems.
Avoid the latter: If you are going to do this you might as well generate some benefits! Leaving the tube open and continuing to use a standard spider is not a clever way of doing it! Get a good quality scope with a corrector plate and reap some benefits.
To be fair to the closed tube Catadioptric-Newtonian telescopes: There are three advantages over the simple Newtonian: The tube is closed by the corrector plate and this eliminates tube currents, this lessens the tarnishing of the mirror surfaces, and thirdly, the secondary cell doesn't need a spider to hold it in place, so there is not as much diffraction of the image (But it's still there).
The codes used by manufacturers to describe telescopes usually relate to the various sizes and focal lengths mentioned above: There is a sort of de-facto system that a bit of logic will unravel.
IF some well-meaning soul has bought you a 'tiny telescope' for a present, and having read this guide you know they have bought you something that will fall short of the ideal.
In the interests of checking the accuracy of my claims I bought myself a 70mm f10 Bresser Refractor (off eBay, naturally!). As you know by now this is smaller than my minimum recommended size by 10mm. I did extensive observations of the planets, stars and Messier objects with an aim to either corroborating or re-calibrating my 'minimum' telescope size for you. I feel that I must tell you that this telescope performed well enough for a begginner to get a real feel for astronomical observation. Falling slightly short on the detail on the planets that I was hoping for.
Get to know what a telescope looks like when it is set up. If you come across a telescope that is being advertised (EG on eBay) and the 'scope is obviously upside down, or assembled in a totally whacky manner - Please leave it alone!
You may laugh, and if you don't, you need to learn a bit more about how to set up a telescope.
Seriously, these telescopes could have sustained serious damage being upside-down!
No answer? Move on, buddy!
IF IN DOUBT PLEASE ASK!