Pentax 100 SDUF II High Speed Astrograph Telescope, 400mm f/4.0 SMC 4-Element SD Apo, 100mm Diameter Objective.

The next generation apochromat refractors from Pentax. These SD apochromat refractors are not just improved models of the former PENTAX ED's. As the material of the objective lens is newly developed SD (Super Excellent Low Dispersion) glass, which is very similar to fluorite in optical quality . It is however far more durable and stable.

These models achieve ultimate image quality that can never be expected from any other achromat or ED apochromat refractor. Every lens surface is fully Super Multi-Coated (SMC), yielding highest transmission in every wavelength.

The Pentax 3.9-inch f/4 100 SDUF II, with a built-in field flattener, is an ideal instrument for taking wide-field photos of Milky Way star clouds, huge nebulae, as well as expansive star clusters.

It is mounted on a single-arm bracket, making it look more like a big finderscope than a freestanding telescope. It has a 100mm diameter objective, 400mm focal length, f/4.0, SMC 4-element SD-APO (field flattener included) and a 112mm filter threaded in front of the objective.

The focuser is a precision helical type with a rubber-coated locking clamp (graduations in 0.02mm's equipped). The Eyepiece holder is 2.37"-1.5"- 0.965" ( 58mm -36mm filter threads). The Telescopes Color is a white tube with a Moss green rear end ring.

It's size is 115mm diameter and 436mm length (when dew cap is drawn-in). It weighs 4.0 kg. This is really an astrograph. Its focal ratio is 4 and is optimized for 67 format, too. Many people even use it on 4x5 film.