Avoid Aperture Fever

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Now that the magnification myth is dispelled, you know you need as much aperture as you can afford. Or do you? If you are not careful, you may catch aperture fever. The first signs of it are longer and longer perusals of the telescope advertisements in Sky & Telescope and Astronomy magazines, accompanied by imagining the spectacular views to be had with the Colossal SuperScope. However, be warned. Big telescopes do not always foster contentment among astronomers. Quite a few of our colleagues observe happily with their 14-to-25-inch instruments, and so might you. But without a convenient, dark, permanent site to house such a brute, think very carefully about what you want. The biggest telescope is not always the best.

A 12-inch-aperture telescope will outperform a 6-inch one, all else being equal. That is the catch. All things are rarely equal. Price, for instance. Big telescopes can be expensive. If you lose interest in the hobby, you will have a sizable investment tied up in a telescope that may be tough to sell. Lose interest? Never, you say. Well, lots of people do. The reasons can often be traced right back to big telescopes, which can be awkward to set up and require effort to carry to the backyard or out into the country. For the sin of being too heavy, big telescopes end up collecting dust in closets and basements.

Another problem is the shakes. A large-aperture telescope needs, without exception, a heavy-duty mount. A lightly mounted large-aperture telescope might be more portable, but the images will dance about with every puff of wind and every touch of a hand. An instrument with a flimsy stand is soon banished to the basement.

Big telescopes, especially the less expensive models – those most likely to lure the enthusiast with aperture fever – are often saddled with poorer second-rate optics that prevent them from realizing their full potential. In our experience, well-crafted telescopes in the 4-to-8-inch range can outperform mediocre instruments of much larger aperture. This is partly because the big telescopes are more sensitive to poor seeing, which degrades image detail, particularly on the moon and planets.

Finally, one simple and often-overlooked fact is that large telescopes do not fit into small cars. It is surprising how many amateur astronomers buy or make a huge instrument without considering how to transport it.

Our advice is that the beginner should resist the temptation to buy a first telescope larger than 8 inches in aperture. Performance is much more than simply getting the brightest image affordable. The best telescope for you is the telescope that you will use most often. Of course, affordability is a limiting factor, but even more important is ease of operation. A well-made instrument that is convenient to use will provide a lifetime of enjoyment.

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