The term “roof prism” was originally applied to the Abbe-Koenig (AK) prism design that corrected an image horizontally and vertically while maintaining a straight line from the point at which the light enters the prism and exits it. While the AK prism configuration is the most common, there are others that are variations on the original AK design, such as the Amici and Schmidt-Pechan (SP). While they accomplish the same basic function, the optical paths take different routes to correct the image orientation. The main advantage of the SP design is that it is more compact than both the Amici and AK prisms, resulting in thinner optical tubes that tend to be more comfortable to hold—especially during long glassing sessions. Zeiss is known for using SP prisms.
These Canon binoculars offer something different from the above options because of the image stabilization function. This means that they minimize any shake and are much easier to use by hand – you just push the image stabilization button and the shaky image steadies. This means that for casual stargazing and astronomy, they can be used without a tripod.
Optically, the TrailSeeker offered exceptional light-gathering abilities. I remember watching a northern harrier soaring against the sky and the colors of the streaks below were as sharp as can be. Another bonus is this pair’s ability to focus close—as near as 6.5 feet, with a field of view of 426 feet at 1,000 yards. However, the outer edges of that expansive field of view had some mild distortion. The streaks on a Lincoln’s sparrow got a little mushy through the edges of the Celestron lenses, yet remained razor-sharp through the lenses of the Athlon Optics Midas ED. Most users probably won’t notice this, but the Athlons were clearly superior, to my trained eye.
For the mechanics, Fujinon was the first company to have developed stabilization with high-speed gyroscopes and they brought this feature to market as the "Stabiscope" in 1980 with a 14X binocular. The design was improved and the Techno Stabi introduced in 1999 at price points that make it competitive with the Canon offerings. This stabilization approach works particularly well in adjusting for large movements, such as experienced with vessels on water, but also does admirably with smaller movements. Fujinon optics have earned their reputation for excellence and provide an above average crisp, clean, and bright viewing experience.
There are zoom binocular rangefinders which let you use the variable magnification feature. In these, you have the opportunity to change the magnification depending on the range they offer. If the rangefinder binocular is denoted as 7-15×40, you have the ability to adjust the magnification from 7x to 15x. This can be done by turning a lever or wheel which is placed at the center of the binocular perfectly within reach to your thumb or index finger. This offers great versatility to your rangefinder binoculars magnification. But at the same time, it can hamper the quality of the image if deliver.
You’ll want to start your moon-gazing when the moon is just past new – and visible as a waxing crescent in the western sky after sunset. At such times, you’ll have a beautiful view of earthshine on the moon. This eerie glow on the moon’s darkened portion is really light reflected from Earth onto the moon’s surface. Be sure to turn your binoculars on the moon at these times to enhance the view.
But, in practice, the radiant is an area at least 10 degrees across. You will spot more meteors with a wider field of view. [Note: You'll probably see the most with your unaided eye.] Higher power does you little good; the greater magnification of those fireballs you do catch will only dazzle your eyes, making it more difficult to see smaller ones immediately afterward.