Explore Scientific ED115mm f/5.5 Air-Spaced APO Triplet CF Refractor (OTA Only)

Ideal for visual observation and astrophotography, the Explore Scientific's ED115mm f/5.5 Air-Spaced APO Triplet CF Refractor strikes a delicate balance between aperture and weight, making it ideal for lunar, planetary, and deep-sky viewing while still being highly portable. Its relatively compact form factor makes it perfect as a fast grab-and-go option, or to be set up on a dual-mount rig for astrophotography/astroimaging. Using Ohara FPL-53 extra low-dispersion (ED) glass in an apochromatic air-spaced triplet lens configuration, with fully multi-coated optics, produces images that are clear and bright without fringing, halos, or distortion across the entire field of view, with true color rendition and high contrast. The fast focal ratio, when combined with the optical performance, makes this an ideal astrograph to capture images with accurate colors and limited distortion across the entire field of view.

To handle large imaging rigs and accessories, Explore Scientific outfitted the OTA with a heavy-duty focuser to carry imaging gear and accessories. Using a traditional rack-and-pinion mechanism makes it more solid and sturdy than comparable Crayfords, while the large 3" hexagonal drawtube is stronger and less prone to flexing than conventional round tubes. When put together, the focuser, by itself, has an impressive payload capacity of 10 pounds — allowing it to comfortably carry the heaviest of astrophotography rigs with ease. A two-speed system allows for fast coarse, then precision fine focusing to ensure the most sharp and crisp views possible.

Offered here as an OTA-only option for those with reliable support systems, the carbon fiber tube weighs just 15 pounds to be easily carried by even medium-sized mounts. A cradle ring set is included, with an integrated handle for safer setup and breakdown. A Vixen-style dovetail plate makes it compatible with a wide array of alt-azimuth, equatorial, and GoTo mounts. The cradle ring assembly also allows the orientation and position of the OTA relative to the mount to be adjusted for better balance and to avoid interference with equipment or mount. The OTA's carbon fiber construction also resists the expansion and contraction common in metal tubes when moving between extreme temperatures, which can cause the internal lens elements to move out of alignment over time, affecting the scope's ability to achieve sharp focus and causing fringing and halos.

Whether you want an OTA for fast observation without compromising image quality, or a fast OTA that produces bright and clear images of the moon, planets, galaxies, nebulae, or star clusters, this Explore Scientific optical tube assembly is ideal.