1. Bishop, R. "Binoculars." In R. Gupta, ed., Observer's Handbook 2003. Toronto: University of Toronto Press, 2002, pp. 50, 51.

2. Adler, A. "Some Thoughts on Choosing and Using Binoculars for Astronomy." Sky and Telescope, 104 (3), September 2002: 94-98.

3. Zarenski, E. How-to Understand Binocular Performance. documents/performance.pdf.

4. Seronik, G. "Image-Stabilized Binoculars Aplenty." Sky and Telescope, 100 (1), July 2000: 59-64.

5. Seyfried, J.W. Choosing, Using, & Repairing Binoculars. Ann Arbor: University Optics Inc., 1995, pp. 10ff, 47.


- Evaluating


Recently, a colleague told us of a local gas station that was offering 10x22 compact binoculars for sale at under $5 each. On the reasoning that "you can't go wrong at that price," the colleague acquired a pair for his son, who was very pleased with them. Upon hearing of this, another colleague went to the gas station and bought a pair for herself. When she got home and tried them out, she found that they gave a double image, obviously a case of poor collimation. She returned them, where the sales assistant took them and, without even checking them, placed them in a box and replaced them with a new pair out of another box. My colleague was satisfied with the replacement pair and pleased with the "service" she received from the gas station.

A few weeks later, I took a group of students to see an international cricket match; one of them was the son of the first colleague, who brought his new binoculars with him. As usually happens, these binoculars were passed around among the students, most of whom had never used binoculars at a sporting event, and they were impressed with the magnified image and wanted repeated looks through the binoculars. To ease the demand, I passed around my good (but by no means superb) quality 10x42. Every student immediately noticed the difference and it was obvious that none had used binoculars of this quality before. As one put it: "These are amazing,Mr. Tonkin. They are even clearer than eyesight!" The colleague's son was, as you can imagine, a bit deflated because his binoculars seemed so inferior. I pointed out that mine had cost almost exactly a hundred times the cost of his. I showed the students how to detect the off-axis chromatic aberration and pincushion distortion in mine, and then asked them to consider if they thought that the image in mine was a hundred times better. I also pointed out that mine could not be conveniently carried in a shirt pocket. Honor was satisfied and we got on with enjoying the match, albeit with my binoculars having far more use than the budget ones. This pair of episodes illustrates several things:

• Over the past few decades binocular manufacturing methods have improved to the extent that, without any but the most rudimentary quality control checks, binoculars of reasonable quality can be produced remarkably cheaply. Budget quality binoculars can be produced so cheaply that they are effectively disposable items.

• It is far more cost-effective for manufacturers of all but the best quality binoculars to use the customer to do the quality control. It is cheaper merely to replace the unsatisfactory (to the customer) instruments than it is to employ quality control staff.

• People will tend to be satisfied with poor quality unless they have something better with which to compare it. The consequence of this is that many instruments, which may have been rejected by effective quality control, will be acceptable to some customers, particularly if the price is right.

• Differences in optical quality can often be immediately apparent, even to "untrained" people, most of whom are capable of performing simple tests for common aberrations.

• Once you have used good quality binoculars it is difficult to be satisfied with less. However, we do become emotionally attached to our possessions and can readily justify poor quality on the grounds of price or some other comparative benefit like ultraportability.

• Optics that are entirely free of aberrations exist only in the imagination and, to a large extent, the old adage that you get what you pay for still holds true. For recreational use, the determination of whether the extra quality is worth the extra price is almost entirely a subjective one.

Hence, it is not only possible,but also very desirable, to be able to do some initial testing of binoculars in the store where they are bought. With the advent of the phenomenon that an ever increasing number of goods are bought, for reasons of cost, over the Internet or by mail, the same applies to testing upon receipt of the item. However, as you are aware, there is no substitute for the more demanding tests that astronomical use makes of binoculars, so it is important that you ensure that the vendor has a policy that will permit you to return them if they are unsatisfactory when they are used under the stars.

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