Astro-Tech 5.5mm 1.25″ PF Eyepiece

Description

A CN reviewer barlowed the 5.5mm PF with a 2x Barlow in a 16-inch Dob (530x) and was impressed with the results. That’s extreme magnification, useful only on the steadiest nights, but it confirms the optics hold up under a Barlow. A more practical use is a 2x Barlow in a medium-aperture scope giving you an effective 2.75mm eyepiece at 16mm eye relief.

Accessories

• Astro-Tech PF 10.5mm 1.25″ eyepiece The medium-high power companion. Together with the 5.5mm and 25mm PF, you complete the three-eyepiece starter set Alan Dyer recommended in his Cloudy Nights review.
• Astro-Tech PF 25mm 1.25″ eyepiece Low-power wide-field. The bookend to the 5.5mm from survey to detail in two eyepieces.
• Astro-Tech 2x Telecentric Barlow (AT2XTB) Doubles the magnification of any PF eyepiece while maintaining eye relief. Turns the 5.5mm into an effective 2.75mm.
• Any standard 1.25″ planetary or color filter A light yellow (#8) or blue (#80A) filter can enhance planetary contrast at high magnification.

Final Thoughts

Short-focal-length eyepieces have always been where budget designs hit a wall too few elements to correct the field, too little eye relief to observe comfortably, too narrow a view to enjoy the magnification. The 5.5mm PF pushes through that wall with six elements, 16mm of eye relief, and a 60 field that actually lets you use the magnification it delivers. It was tested at f/4.5 in a 16-inch Dob and held its own. If you observe planets, double stars, or small planetary nebulae and you’ve been putting off buying a high-power eyepiece because the good ones cost ten times this much stop putting it off.

Tech Details: