Sky-Watcher
Sky-Watcher Esprit 100EDX
A three-element ED apo built for the camera: flat, color-free, pinpoint stars across a full frame, a serious astrophotography refractor, not a grab-and-go.
93/ 100
Aperture
100mm
Focal Length
550mm
Focal Ratio
f/5.5
Mount Type
None (OTA only)
Optical Design
ED Triplet Apo Refractor
Weight
6.4 kg
From$2,095
Lowest in 90 days
Price tracked by PolarisObserved 55 timesTracking since Aug 2026
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01What it's good atWhat it's best at — and the trade-offs.
A true triplet ED objective: no visible chromatic aberration, tight stars corner to corner.
01What it's good at
What it's best at — and the trade-offs.
A true triplet ED objective: no visible chromatic aberration, tight stars corner to corner.
Best at
✓A true triplet ED objective: no visible chromatic aberration, tight stars corner to corner.
✓Ships with a dedicated field flattener matched to the optics, so stars stay round to the edge of a large sensor.
✓At 550mm f/5.5 it frames big nebulae and galaxy groups while staying fast enough for short subexposures.
✓Rotatable 3-inch focuser, tube rings, dovetail and a foam case included, a complete imaging OTA.
Trade-offs
!No mount included; it needs a capable EQ mount, which is a significant added cost.
!A camera, flattener spacing and guiding are required to realize the optics.
!100mm of aperture is modest for visual use next to a Dobsonian.
!Premium price for a refractor of this size.
02In plain EnglishWhat These Numbers Mean
100mm · f/5.5 · 550mm FL
02In plain English
What These Numbers Mean
100mm · f/5.5 · 550mm FL
Aperture
100 mm
Four inches of premium apochromatic glass. Enough light grasp for demanding deep-sky imaging and enough optical quality that it also gives reference-grade planetary and lunar views for its size.
Focal length
550 mm
Wide field with real aperture behind it. Large nebulae fit an APS-C frame while galaxies keep usable scale, which is a rare balance and part of why the Esprit line is popular with imagers.
Focal ratio
f/5.5
Fast for a triplet of this quality, so exposures build quickly and guiding tolerances stay comfortable. Combined with the supplied flattener, corner stars stay round across a full-frame sensor.
Optical design
ED triplet apochromat with dedicated flattener
Three-element correction plus a matched field flattener designed for this exact tube, which removes the guesswork of pairing a generic flattener. Colour correction is strong enough that bright stars stay clean in long exposures.
Weight
6.4 kg tube
About 14 lb before rings, camera and guiding. A mid-size equatorial handles it, but this is past the point where a star tracker is enough.
Mount
OTA only
No mount included. For a loaded imaging rig at 550 mm, plan on a tracking equatorial rated around 15 kg with autoguiding to do the optics justice.
03The Polaris ScoreHow it scores, and why.
93/100 · #1 of 4 astrophotography refractors
03The Polaris Score
How it scores, and why.
93/100 · #1 of 4 astrophotography refractors
93/ 100
Sky-Watcher Esprit 100EDX
#1 of 4 astrophotography refractors
Performance96
Ease of use65
Portability80
Upgrade potential90
Polaris weighs optical capability, how easy the scope is to live with, how portable it is, and how far it takes you before you outgrow it — not list price or brand.
04Who it's forAn honest fit check.
Astrophotographers who want a wide-field, deep-sky imaging refractor that will not fight…
04Who it's for
An honest fit check.
Astrophotographers who want a wide-field, deep-sky imaging refractor that will not fight…
Buy it if you
✓Astrophotographers who want a wide-field, deep-sky imaging refractor that will not fight them on stars.
✓Imagers ready to pair it with a solid equatorial mount and a cooled camera.
✓Anyone upgrading from a doublet who wants the last bit of color correction and edge sharpness.
Look elsewhere if you
!Beginners, this is an OTA that needs a mount, camera and imaging train to do its job.
!Visual-only observers, who get more aperture per dollar from a reflector.
!Grab-and-go users who want to set up in seconds.
05Build your rigWhat to buy next — and where it leads.
6 pieces of gear, ordered by what changes the view most
05Build your rig
What to buy next — and where it leads.
6 pieces of gear, ordered by what changes the view most
Recommended upgrades
No fogging on long sessions★ Top pickPegasus Astro Multi-Channel Dew Controller
Prevents fog on your optics during long sessions
$259.90View details →
Make nebulae popOptolong UHC Filter 2″
Improves contrast on nebulae and planets with this setup
Observe all night, no AA batteriesCelestron PowerTank Lithium
Keeps your mount running all night in the field
$99.95View details →
Growth path
Portable astrophotographyZWO AM5N Harmonic Equatorial Mount✓ Compatible
Start capturing images of the Moon and planets
$2,299View details →
Permanent-setup astrophotographySky-Watcher EQ6-R Pro✓ Compatible
Commonly paired with this telescope
$2,250View details →
Start imagingZWO ASI2600MC Pro
Start capturing images of the Moon and planets
$1,499View details →
06The numbersFull specifications.
6 measured and stated values
06The numbers
Full specifications.
6 measured and stated values
Optics
Optical DesignED Triplet Apo Refractor
Aperture100mm
Focal Length550mm
Focal Ratiof/5.5
Mount & drive
Mount TypeNone (OTA only)
Physical
Weight6.4 kg
07AlternativesFor a different goal, start here.
3 alternatives, each mapped to the goal it wins at
07Alternatives
For a different goal, start here.
3 alternatives, each mapped to the goal it wins at
wider field
→William Optics RedCat 51
A compact 250mm petzval for very wide fields at a much lower price.
budget
→Sky-Watcher Evostar 72ED
An ED doublet that is a great, affordable entry into imaging refractors.
all-in-one
→ZWO Seestar S50
If you want images without building an imaging rig, a smart telescope does it automatically.
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