Houdini Eyepiece Specifications
| Eyepiece | Focal Length mm | AFOV ° | Field Stop mm | Layout | Eye Relief mm | Weight g | Diameter mm | Height mm | Barrel | Barrel Length mm | Focal Point mm | Flatness diopter | Angular Magnification Distortion |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Houdini 20 | 20 | 86 | 30.0 | 8 / 6 | 20 / 15 | 570 | 64 | 140 | 2" | 35 | +2 | < 0.7 | < 2% |
| Houdini 12 | 12 | 86 | 18.0 | 9 / 7 | 19 / 15 | 330 | 51 | 121 | 1.25" | 34 | -0.5 | < 0.5 | < 3% |
| Houdini 9* | 9 | 86 | 13.5 | 9 / 7 | 19 / 15 | 310 | 48.5 | 127 | 1.25" | 31 | -0.5 | < 0.5 | < 2% |
| Houdini 7* | 7 | 86 | 10.5 | 9 / 7 | 19 / 15 | 290 | 47 | 129 | 1.25" | 30 | -0.5 | < 0.5 | < 2% |
AFOV = Apparent Field of View
Layout: Number of Elements / Number of Groups
Eye Relief: Theoretical Eye Relief (center of field, to glass) / Effective Eye Relief (edge of field, to body)
Diameter: Maximum diameter of the aluminum body - the rubber grips add around 1 mm to the diameter
Height: Includes the height of the eyecup
Barrel: Standard size 2" = 50.8 mm or 1.25" = 31.75 mm
Focal Point: Position of the focal plane with respect to the barrel. Positive values are above and negative values are below the top of the barrel
* Houdini 7 expected in December 2025, Houdini 9 in March 2026.
Houdini Eyepiece Performance
The following graph illustrates the performance of the Houdini eyepieces in a F/4 Newtonian telescope. Spot diagrams with 3,000 rays are shown at the center, halfway, and near the edge of the field.
The spots have been strongly magnified to show them clearly. In the center of the field a spot diagram smaller than 2' is almost perfect, at the edge a spot diagram smaller than 10' is considered excellent. The top left shows 2' and 5' circles.
There is no trace of coma left in the Houdini spot diagrams. Some spherical aberration and some lateral color remain, which shows on very bright objects, such as a magnitude 1 star or Jupiter, at the edge of the field. This is not visible at all in a typical deep sky field that does not contain magnitude 1 stars. Such a field will appear essentially sharp from edge to edge.
