Big subject that's a bit hard to summarise. However...
1. Celestron and Meade aren't the only brands worth considering, but they are the best combination of quality and value in the 'affordable' price range.
2. The usual advice to beginning astronomers is *not* to get a telescope but to buy a decent pair of big binoculars. They're cheaper, will get used more, and teach you more. Everyone ignores this advice
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3. In grossly oversimplified terms, the most important thing about an astronomical telescope is the size of the optics. Bigger is better (and more expensive). Scopes can be split into two kinds: refractors, which use a primary lens, and reflectors, which use a primary mirror. Simple rule of thumb: lenses are better and more expensive; mirrors are cheaper but give you more size for your money.
4. Nearly as important is a good tripod. Make sure any scope you buy meets this requirement.
5. Your budding stargazer must understand (if he doesn't already) that what he sees on Sky at Night is typically *not* what he's going to see through the average amateur scope. Only long-exposure astrophotography delivers those kind of images.
6. All scopes - like most things in life - are a compromise among a number of desirable features: price, quality, light grasp (big optics), motor drives, 'goto' computers, etc. If he wants to do astrophotography, motor drives are essential. If just wants to see interesting stuff without learning astronomy in depth, the goto computer might be important.
7. The Celestron C4-R is a good refractor (lens at the front). This makes it very long and hence a little inconvenient to carry to the bottom of the garden. For the same price you could go for the Celestron C4-N, which is a reflector with a bigger mirror and a shorter tube. Or there's a NexStar 4GT (i think) which is similar in size to the C4-N but has the goto computer.
Meade almost certainly have models that are identical to these, at similar prices.
I'm sure you'll have more questions... ask away
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