Celestron's C102 HD is a 102mm (4") diameter, glossy black tubed refractor, equivalent to a 1000/f10 focal length lens. Carefully designed for the more serious astronomer and terrestrial observer and feature exquisite optics and precision, heavy duty mounts. Optics are made to exacting standards, with high quality materials to ensure top performance. Astronomical viewing is a delight with these large, powerful 4" telescopes, offering 63% increase in image brightness over 80mm models. The larger aperture delivering incredible images of the moon, Saturn and its ring structure, Jupiter and its belts and hundreds of deep-sky objects, including galaxies, nebulae and star clusters. Includes heavy duty CG4 German equatorial mount, RA & DEC slow motion controls and setting circles, 6x30 finderscope, 20mm 1.25" plossl, diagonal, djustable aluminum tripod with accessory tray. Optional motor drives 93517 or 93522 available. Adaptable for astro and telephoto photography with optional T-Adapter 93625, combined with T-Ring matched to your SLR body. Eyepiece size: 1.25".