Buying binoculars can be confusing. What do all those numbers mean and why do you care? Which is better 10x50 or 12x25? This guide can help you sort through the confusion and make the right decision for your needs.
PowerThe power of the binoculars is the level of magnification. This is denoted by the first number. Binoculars that are 10x50 are ten power. They will allow you to see at 100 yards as though you were 10 yards away. This is probably the single most important factor in your decision. For NASCAR you want to look at binoculars that are in the 7 - 12 power range, the higher the number the better.
FocusBeing able to focus quickly is important since things happen fast at the track. There are three types of focus methods found on binoculars today. "Permafocus" and "Instafocus" are trademarks of the first type. These are pre-focused for you and can save you time. Second is a center rocker-arm focus. This is not quite as fast but will generally give you good results. Third is the center barrel focus where you twist a knob. This type is the slowest of the three.
DiopterYou should verify that any binoculars you buy have a diopter adjustment ring on the right eyepiece. This adjustment allows you to configure the binoculars for your specific eyes.
SizeThe physical size of the binoculars can make quite a difference in how comfortable and convenient they are for you to use. Smaller, lighter binoculars will be much more comfortable hanging around your neck for four or five hours. Given two binoculars that are equal in every other way, take the smaller ones.
Objective LensThis is the "other" number, that is, those 10x50 binoculars are ten power, but have a 50mm objective lens. The larger the second number the more light the binoculars will let in. While this is important for bird watchers and star gazers most NASCAR races are pretty well lit. :) If you are only using your binoculars for NASCAR then the objective lens measurement is much less important to you.