William Optics has developed the ZenithStar 61 to be the most versatile and portable instrument they've ever produced. Combined with any DSLR camera, the ZenithStar 61 offers superb, sharp images for astrophotography or wildlife photography. It can used in high power for visual applications as well as with a large image circle for photographing the Moon when used with a dedicated Flattener 61 (sold separately). The ZenithStar 61 is a great telescope you'll be able to enjoy for many years!
The objective lens uses FPL-53 glass which is a significant improvement over the older FPL-51 ED glass. ED and SD glass dispersion properties are critical to ascertain the general color correction. The abbe index is the number used to quantify the "partial dispersion" of a specific glass. FPL-53 glass features a partial dispersion that is so close to pure fluorite, which has the highest partial dispersion of any material at around 95 V, that it has been referred to as synthetic fluorite.
           FPL53 is top notch glass material that allows William Optics designers to achieve the best color correction. It is also the most expensive glass on the current market.
When you purchase a telescope from William Optics, you can be assured that your instrument was tested on their Interferometer. Furthermore, each telescope is individually star tested by William Optics professionals to guarantee the ultimate in optical quality.