Sky-Watcher Esprit 100ED 100/550 f/5.5 Pro OTA Apochromatic Refractor Telescope
The Sky-Watcher Esprit 100ED is a premium apochromatic ED triplet refractor built for astrophotographers and demanding visual observers who refuse to compromise on image quality. The 100mm objective combines an Ohara FPL-53 ED lens with two additional lenses, delivering outstanding colour contrast and virtually no chromatic aberration - even when observing the brightest objects in the sky. A field flattener is included and screws directly onto the focuser, so the telescope is ready for astrophotography with no extra accessories required.
Ohara FPL-53 glass - why it matters
Ohara is a German optical glass manufacturer based in Hofheim in the Taunus mountains and is recognised as one of the world leaders in optical glass research and production. Ohara developed the FPL glass series specifically for astronomical applications. The exceptionally low dispersion of FPL-53 glass is the key to the sharp, high-contrast images that the Esprit 100ED delivers.
Who is this telescope for?
- Astrophotographers looking for a ready-to-use imaging telescope with a field flattener included
- Visual observers who demand the highest colour accuracy and contrast
- Anyone who wants a professional-grade APO refractor without the need for additional optical accessories
Key features
- Apochromatic ED triplet objective - virtually zero chromatic aberration
- Ohara FPL-53 extra-low dispersion glass
- Objective aperture: 100mm
- Focal length: 550mm
- Focal ratio: f/5.5
- Screw-on field flattener included
- OTA only - no mount included
Technical specifications
| Parameter |
Value |
| Optical design |
Apochromatic ED triplet refractor |
| Objective aperture |
100mm |
| Focal length |
550mm |
| Focal ratio |
f/5.5 |
| Lens glass |
Ohara FPL-53 ED |
| Field flattener |
Included (screw-on) |
| Supplied as |
OTA only |
What is an apochromatic refractor?
A standard refractor lens bends different colours of light by slightly different amounts, which causes coloured fringes around bright objects - this is called chromatic aberration. An apochromatic (APO) lens corrects this across three wavelengths of light instead of two, and a high-quality ED glass element such as Ohara FPL-53 reduces residual colour fringing further still. The result is a sharper, cleaner image with true colour accuracy - essential for both serious visual observation and astrophotography.
Specifications
Type of telescope:
ED & Apochromats
Optical scheme:
Apochromat Triplet
Focal length:
550 mm
Aperture:
100 mm (4″)
Aperture ratio:
5.5
Resolving capacity:
1.4"
Limit value:
13.8 magnitude
Light gathering capacity:
204x
Product range:
Esprit
Max. useful magnification:
200x
Connection type:
3″
Mounting:
No mount
Recommended for:
Advanced, Experienced
Application area:
Astrophotography, Deep Sky observation, Planets observation, Nature observation
Package contents of "Apochromatic Refractor Sky-Watcher Esprit 100ED 100/550 1:11 Pro OTA":
✅ ED refractor 100/550mm
✅ Threaded reducer 3″/2″
✅ Reducer 2″/1.25″
✅ M48 adapter
✅ Rings and Vixen-style rail
✅ 9x50 finder scope
✅ 2" zenith mirror
✅ Carrying case
Typical magnifications
The recommended magnification is highlighted in yellow.
D = telescope aperture in millimeters
