Sky Talk July 2008: In Praise of the 60mm Refractor

The ubiquitous 60mm (2.4-inch aperture) refractor is without question the most common telescope in the world. Literally millions of these glasses have been sold over the years. They can make a great choice for beginning stargazers and an ideal, highly-portable second instrument for experienced observers owning much larger scopes. And while their performance can sometimes be excellent, they more typically leave much to be desired both optically and mechanically. Here’s some tips on what to look for.

The achromatic objective lenses of most 60mm refractors (nearly all of which are imported from the Orient) are of good, and in some case truly excellent, optical quality. Unfortunately, the use of a combination of inferior components for other parts of the instrument mask this quality and have given them a reputation as being “trash telescopes” or sometimes referred to as “department store telescopes.” One of the weakest links is the eyepieces supplied with them. Not only are these often of very poor quality and way over-powered, but until recent years most were of the “sub-diameter” (sometimes called “Japanese-size”) variety, having .965” barrels and housing very small lenses. This is in marked contrast to the “American standard size” barrel 1.25” in diameter, which allows using larger and better-quality optical elements, as well as providing a much wider and more comfortable field of view in looking through them.

Another area where quality is skimped on is the finder scope mounted onto the main telescope to aid in locating objects. These typically are so small and have such poor optical quality that they are nearly useless in aiming the telescope. Even more disturbing is the increasing use today of plastic in place of metal for various components of the telescope, including the main tube, focusing mechanism, finder and even some parts of the mounting itself. And speaking of mountings, you may have the finest telescope in the world but if sits atop a poor mounting as many 60mm refractors do — one that vibrates at the finest adjustment of the focuser or shakes in the slightest breeze — it will perform poorly and leave you frustrated.

We are very proud to say that the Scientifics’ 60mm refractor (#30823-61) avoids the above problems. Carefully designed with the beginning stargazer in mind, it will reveal a lifetime of wonders ranging from the Moon and planets, to colorful double and multiple stars, glittering star clusters, eerie-looking nebulae and even many of the brighter galaxies themselves! And it wonderfully illustrates the truth of the well-known rule-of-thumb in astronomy that “the smaller (more portable) the telescope, the more often it will be used.” Weighing-in at just 6 pounds, it’s easily moved about and always ready for instant use.

Note that we did not mention viewing the Sun above. Observing our “Daytime Star” can be very fascinating — but it’s also very dangerous, carrying with it the threat of serious eye damage or even blindness unless proper safety precautions are taken. Since this installment of Sky Talk is devoted to the 60mm refractor, we issue a warning here as a service to our readers. Many imported refractors of this size come equipped with an accessory typically labeled “Sun Filter,” “Sun Cap” or simply “Sun.” Designed to be screwed into one end of the eyepiece for looking at the Sun through the telescope, these are deadly devices! With the Sun’s heat being collected and focused by the telescope’s objective lens directly onto the filter, it heats it up to such a degree that it can burn eyelashes, the cornea of the eye, and in some cases gets so hot that it cracks and shatters. The safest way to view the Sun (other than eyepiece projection, which often destroys eyepieces) is to use a specially-designed full-aperture filter over the main objective, blocking its fierce light and heat before they ever enter the telescope.

–James Mullaney
Former assistant editor at Sky & Telescope magazine and author of five books on stargazing.

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