Eye to the Telescope

A good “entry level” telescope is a Newtonian reflector. They are a simple design and relatively low priced for the size of mirror you’ll get for your money – ideal if you’re just starting out.

150 PDS Newtonian Reflector

A Newtonian reflector with a 6-inch mirror will give you good views of the brighter galaxies and nebulae and should also perform well when you train it on the Moon and planets.

120 ED Refractor

But what about the other types of telescope? Refractors are perhaps the most familiar designs. They use a series of lenses to bring what you’re looking at to focus at the eyepiece end of the tube and are great for observing the Moon or relatively bright star clusters.

8 inch Dobsonian Reflector

There’s also the Dobsonian, which is a type of reflector that has a simple mount and because of that, often has a much larger mirror for its price. As this collects more light it will let you see dimmer objects, so it’s a great choice if you want to see faint galaxies and nebulae.

127 Maksutov Cassegrain (Catadioptric)

Finally, there are the catadioptric telescopes that use a combination of corrector lenses and mirrors. Their compact size makes them relatively portable and their high focal ratios mean that they’re ideal for lunar and planetary observing.

How much money should I spend?

A good Newtonian on a sturdy equatorial mount costs around £300 in the UK, while a good refractor costs around £360. A 6-inch Dobsonian can cost as little as £210. What’s most important is that you buy from a well-respected astronomical dealer.

Avoid the cheap, poor-quality models you sometimes see in mail order catalogues or in high street stores.

Don’t be fished in by the stunning visuals either in adverts or on the box, every Telescope manufacturer is guilty of this. They cover the box in stunning images from the Hubble Space Telescope, beginners can be disappointed that they can’t see the blues, pinks and purple in the Orion Nebula, so the kit ends up on Ebay, or even worse, in the loft.

As this blog progresses you’ll see that I refer to certain objects as “Fuzzy Grey Blobs” or Fuzzy Patches” in particular those objects on the Messier catalogue (more on that later)

Most telescopes will have one or two eyepieces included in the price. They come in two standard barrel sizes to fit into the telescope focuser – 2-inch or 1.25-inch – and have several optical designs such as Plössl, Nagler or orthoscopic.

The number on the eyepiece is its focal length, measured in millimetres. The smaller the number, the greater the magnification it will give when used.

Two good quality eyepieces with a small (10mm) and a larger (20-40mm) focal length will provide you with a decent range of magnifications to get you started. Only buy eyepieces that have quality glass lenses, because sub-standard glass or plastic lenses will almost always disappoint.

The other thing to watch out for is if your potential new telescope is “Bragging” about its magnification, this is generally a, very poor, indication of the ‘scope potential magnification. This is how much it would magnify an object if you were using a very short focal length eyepiece with a very high Barlow lens, A Barlow lens is an eyepiece that has an open end for an eyepiece to be attached to the Barlow lens. The front of the Barlow lens goes into the eyepiece socket on your telescope. Barlow lenses usually have a mark on them which indicates the “power” of the Barlow, this is generally X2 or X3. Because a Barlow lens alters the magnification of an eyepiece, having a Barlow lens effectively doubles the number of eyepieces you have. (5 eyepieces and a 2x Barlow = 10 eyepieces)

To work out the magnification divide the focal length of the ‘scope by the focal length of the eyepiece.

Using my 6-inch Newtonian with a 25mm eyepiece as an example: 750÷25=30 x magnification, if I add a 2x Barlow then I get 60 x, a 3x Barlow will give 90x. However, this last result is utterly ridiculous and I really would bother with it unless I was wanting to view the moon or a planet. Realistically this much magnification is way over the top.

Probably the most important aspect of a telescope is the aperture, the wider this is the more light is going into the ‘scope. Focal length is secondary, but still worth considering.

Go-To telescopes come with an in-built computer and handset that, once set up correctly, automatically aim the telescope and track an object. Although this is helpful, it’s probably best to get a scope without Go-To as your first-time buy.

If you aren’t familiar with using a telescope, setting up a scope without Go-To is much easier. A non-Go-To is also much cheaper and will be a gentler introduction to how telescopes work.

What really matters is your budget, a good society or a reputable retailer will be more than happy to offer you advice on your first purchase.

It is worth considering a good pair of binoculars as a first purchase. They can be reasonably priced, extremely easy to use and can also be used for terrestrial viewing..