Houdini 2× Coma-Correcting Barlow
Optimized for use with the 1.25" Houdini eyepieces, this Barlow corrects 75% of the Newtonian coma, while the remaining 25% is corrected by the eyepieces. The result is a number of high-power combinations that are essentially diffraction-limited over the entire 86° field.
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Description
The Barlow is a doublet design using advanced glass types in a 1.25" barrel. It has a modular body with a T2 connector, a centering clamp, and a detachable cell containing the optics. Another nice comfort feature is that the Barlow is designed to be parfocal with all the 1.25" Houdini eyepieces.
When the whole Houdini line-up is complete, you'll have 12, 9, 7, 6*, 5.3, 4.5*, 4, 3.5*, 2.65* and 2* mm coma-corrected 1.25" eyepieces. The * denotes the focal lengths obtained with the Barlow.
The doublet has a 27 mm clear aperture, providing full illumination across all 1.25" eyepieces.
How does it work?
The Barlow is designed to provide correction for 75% of the Newtonian coma from the parabolic mirror.
The Houdini eyepiece that follows will see a light bundle with twice the original focal ratio. For example, an F/4 bundle becomes F/8 after the Barlow. Since the effect of coma correction decreases with the square of the focal ratio, the eyepiece will only correct 25% of the Newtonian coma.
The 75% correction provided by the Barlow, combined with the 25% correction from the eyepiece, produces essentially perfect correction of the original coma. Ray tracing of the 1.25" Houdini eyepieces used with the Barlow demonstrates that this produces high-power combinations that are essentially diffraction-limited over the entire 86° field.
Specifications
| Power | 2× |
| Height | 107 mm |
| Weight | ? g |
| Barrel | 1.25 inch (31.75 mm) and 2 inch (50.8 mm) |
| Clear Aperture | 27 mm |
| 1.25" Barrel Length | 57.5 mm |
| 2" Barrel Length | 37.4 mm |
| Focal point | 0.5 mm below top of 1.25" barrel |
| Provided backfocus | 49.5 mm |
| EAN |