Astrozap Focusing Cap w/ Built-In Bahtinov Focusing Mask For Most 130mm Aperture Refractors

AstroZap Focusing Cap with Built-In Bahtinov Mask – For Most 130mm (5.1") Refractors

When you're working with a high-performance 130mm refractor, especially for imaging, precise focus isn't optional—it's essential. The AstroZap Focusing Cap with Built-In Bahtinov Mask makes achieving that perfect focus fast and repeatable, all while protecting your telescope’s optics when not in use. Designed to fit most 130mm refractors, this clever cap combines two essential tools in one streamlined, easy-to-use accessory.

Built into the front cap is a precision-cut Bahtinov focusing mask, which is accessed via a sliding shutter. Simply slide open the cover, center a bright star, and use the resulting diffraction spike pattern to fine-tune your focus. As you adjust, the central spike shifts position—when it lines up perfectly between the outer two, you’ve nailed it.

Once focused, just close the shutter, and your cap returns to duty as a protective dust shield for transport or storage. No more digging through your gear bag or fumbling with loose accessories in the dark—this cap is always in place and ready to work.

Features:

• Fits most 130mm (5.1") aperture refractor telescopes

• Combines a dust cap with a built-in Bahtinov focusing mask

• Sliding shutter mechanism allows quick transition between focus and storage modes

• Achieves fast, ultra-precise focus using Bahtinov diffraction pattern

• Lightweight and rugged for regular use in the field or observatory

• Ideal for imaging, visual observing, and collimation checks

Compatibility Note:

Sized to match the outer diameter of typical 130mm refractor dew shields or lens cells. Fit may vary slightly between manufacturers—contact us for assistance if you're unsure about sizing.

Observing Tip:

130mm refractors hit a sweet spot for portability, resolution, and contrast. But when paired with high-resolution cameras or narrowband filters, critical focus gets very picky. A built-in Bahtinov mask lets you lock in perfect sharpness without adding bulk or interrupting your workflow.