Houdini 20mm 86° Coma-Correcting
The first eyepiece with a coma corrector built into the barrel, this 20mm shows a fast Dobsonian pinpoint stars across a huge 86° field with no separate Paracorr. It is the low-power wide-field to own if you observe at f/5 or faster.
At 20mm this is a low-power, wide-field eyepiece for framing large nebulae and star fields at a bright exit pupil. It is not a planetary or high-resolution eyepiece, and its coma correction is meant for fast Newtonians, not slow SCTs or refractors.
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Price tracked by PolarisObserved 43 timesTracking since Jul 2026
What it's best at — and the trade-offs.
One eyepiece. A different job in every scope.
An eyepiece has no magnification of its own — the telescope decides. The same eyepiece becomes 24× and 3.6° of sky in a little refractor, or 102× and a tight frame in a long SCT. Here’s what it does across common scopes.
The numbers, in plain English.
The targets this eyepiece was born for.
Where it sits in your eyepiece case.
A good eyepiece collection isn’t a pile of glass — it’s two or three focal lengths that hand off from wide to tight. This is the anchor at the bottom of the ladder: the one you find and frame with. You buy it once, and it stays your low-power eyepiece for life.
What it pairs with.
How it scores, and why.
It earns its standing on a genuinely novel idea executed well: built-in coma correction that keeps stars sharp to the edge of a huge field in exactly the fast scopes where ordinary wide-fields fall apart, with eye relief comfortable enough to actually use the whole view. It gives up ground only on an unproven brand track record and on being wasted effort in scopes that have no coma to correct.
Polaris weighs how well the eyepiece does the job it was designed for — optics, immersion, comfort and value — never list price or brand.
An honest fit check.
Full specifications.
For a generation, owning a fast Dob meant accepting comet-shaped edge stars or bolting a $500 Paracorr onto the focuser. The Houdini quietly folds that correction into the eyepiece itself, and the first time the outer edge of an 86° field stays needle-sharp in an f/5 scope, the trick feels a little like magic. The name fits.
For a different goal, start here.
Explore Scientific 28mm 68°
A proven 2-inch low-power eyepiece for less, if your scope is slow enough that coma is not a problem.
Tele Vue Panoptic 24mm
The classic 2-inch wide-field, though it needs a separate Paracorr to match this edge sharpness in a fast Dob.
GSO SuperView 30mm 2-inch
A wider, cheaper low-power view for slow scopes where edge coma never shows up.