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

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

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

B&H # EXWD115F553F MFR # FPL53-115CF-T3
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Expected availability: 7-14 business days

Includes Free

Value: $35.00

Product Highlights

  • 115mm Aperture Refractor OTA
  • 632mm Focal Length, f/5.5 Focal Ratio
  • Apochromatic Triplet Lens Configuration
  • Ohara FPL-53 Extra Low-Dispersion Glass
  • Proprietary EMD Enhanced Multi-Coatings
  • 3" Starlight Feather Touch Focuser
  • Vixen-Style Dovetail Plate
  • Lightweight Carbon Fiber Optical Tube
  • 90° Dielectric-Coated Star Diagonal
  • OTA Only: Mount and Tripod Required
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Focuser: 3" Starlight True Focuser

3" Hexagonal Rack-and-Pinion

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3" Starlight True Focuser

Aperture: 115mm f/5.5

115mm f/5.5 140mm f/6.5

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165mm f/7

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Price:  $3,874.99

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Explore Scientific FPL53-115CF-T3 overview

  • 1Description

Ideal for visual observation and astrophotography, the Explore Scientific's ED 115mm 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.

This iteration of the OTA benefits from an upgraded Starlight Instruments True 3" FeatherTouch focuser. Its 10:1 two-speed system allows for fast coarse and fine precision fine focusing to ensure the most sharp and crisp views possible, with an easy-to-read scale etched into the drawtube for precise repeatability. Using a traditional rack-and-pinion mechanism makes it more solid and sturdy than comparable Crayfords, while the large 3"-diameter drawtube is stronger than the smaller tubes normally used. When put together, the focuser can comfortably carry heavier astrophotography rigs with ease, up to 15 pounds, while offering the precision focusing required for astrophotography.

Offered here as an OTA-only option for those with reliable support systems, the carbon fiber tube weighs just 15 pounds, and can be supported 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.

Optical Tube Assembly
  • Large 115mm aperture is ideal for lunar and planetary viewing with the ability to see bright deep sky objects
  • Fast f/5.5 focal ratio is useful for astrophotography, as shorter exposure times are required
  • Short 632mm focal length produces a fast focal ratio and less internal light diffusion for bright images and views
  • Refractor-style optical design produces less chromatic aberration than reflectors
  • Extra low-dispersion (ED) Ohara FPL-53 glass corrects chromatic aberration, for improved color rendition and contrast without halos, astigmatism, off-axis comas, and color fringing
  • Apochromatic triplet optical design virtually eliminates spherical and chromatic aberrations for views without distortion across the entire field of view, as well as accurate color representation
  • Proprietary anti-reflection EMD enhanced multi-layer coatings on all optics improve light transmission, color rendition, clarity, and contrast
  • Resolution: 0.9 arcsec, Dawes Limit
  • Carbon fiber optical tube reduces weight without sacrificing strength, and resists the expansion/contraction caused by temperature fluctuations, which can cause internal lenses to move out of alignment and affect image quality and focusing ability
  • Retractable dew shield keeps condensation off objective for clearer views — especially when moving from warm interiors and colder exteriors
Starlight Instruments Focuser Details
  • Sturdy rack-and-pinion design allows it to carry heavier eyepieces, accessories, and imaging rigs without flexing
  • Large 3"-diameter drawtube ensures full coverage of large imaging sensors, preventing vignetting of view
  • Two-speed mechanism allows for fast coarse and extremely precise fine focusing to resolve tack-sharp images, with a 10:1 reduction ratio
  • 1.5" drawtube travel with extensions for applications that require more travel such as when using certain eyepieces or performing prime-focus astrophotography
  • 2" holder accepts larger eyepieces and accessories
  • Heavy 15-pound (6.8kg) payload capacity to carry large imaging systems
  • Optical tube assembly (OTA) only: Mount and tripod required for proper use
  • Mounting ring assembly has an integrated handle for more secure setup and breakdown
  • OTA placement is adjustable on mounting ring assembly for precise balancing, and for finderscope and focusing knob orientation
  • Vixen-style dovetail plate is compatible with a variety of mounts
  • Lightweight and durable carbon fiber optical tube weighs 15 pounds
Included Accessories
  • 2" snout and holder accepts larger eyepieces and accessories
  • 90° angle places head in a comfortable position — especially when the OTA is aimed at or near the zenith
  • Star diagonal configuration corrects view horizontally, but not vertically
  • Highly reflective dielectric-coated mirror limits light loss and pushes transmission to greater than 99%
Reducer adapter:
  • 2"-to-1.25" reducer allows the use of the more common 1.25" eyepieces and accessories
Spacer rings:
  • Set of two spacer rings allows the back-focus distance to be increased and place the focal plane directly on imaging sensors
Carrying case:
  • Hard exterior protects case during transport and storage
  • Custom-cut foam lining perfectly fits OTA and accessories
  • Reinforced edges and corners
  • Hinged carrying handle
  • Dual snap-lock latches secures and seals lid from dust
Finder bracket:
  • Pre-mounted for user-supplied finderscope


UPC: 812257019045
In the Box
Explore Scientific ED115mm f/5.5 Air-Spaced APO Triplet CF Refractor (OTA Only, Starlight FeatherTouch Focuser)
  • 2" 90° Star Diagonal
  • Eyepiece Reducer Adapter
  • Hard Carrying Case
  • 2 x Back-Focus Extension Ring
  • Limited 1-Year USA Warranty, Extendable to Transferrable Lifetime Warranty with Registration
  • Table of Contents
    • 1Description

    Explore Scientific FPL53-115CF-T3 specs

    Optical Design Apochromatic air-spaced triplet refractor
    Aperture 115mm
    Focal Length 632mm
    Focal Ratio f/5.5
    Eyepiece Barrel Diameter 2"
    1.25" with included adapter
    Diagonal 90° star
    2" snout and holder
    Finderscope None
    Tripod None
    Mount Type Vixen-style dovetail
    Optical Tube Dimensions Diameter: 4.5" / 11.5 cm
    Length: 26.0" / 66.0 cm, with dew shield
    Length: 23.8" / 60.4 cm, without dew shield
    Weight 15.0 lb / 6.8 kg

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