TelescopesPlus - The #1 Online Store for Telescopes and Accessories

AstroZap Full Aperture Aluminum Bahtinov Focus Mask for 2.5" - 5.5" OD Telescopes - AZ501

AstroZap Full Aperture Aluminum Bahtinov Focus Mask for 2.5" - 5.5" OD - Main image
$24.82 $38.78 In stock

Category: Telescope Accessories

AstroZap Bahtinov Focus Mask for 2.5" to 5.5" OD Telescopes

The AstroZap Bahtinov is a full-aperture focusing mask that is produced using aluminum for hassle-free application. The bahtinov includes adjustable grommets for telescopes with a 2.5" - 5.5" (63 mm - 139 mm) outer diameter. The thin construction allows for enhanced performance.

AstroZap Bahtinov Focus Masks

All observers and imagers are aware of the fact that sharp focus is necessary for making the most out of your valuable time with the telescope. The Bahtinov-style mask has now passed the Hartmann mask in popularity due to its novel diffraction pattern that enables higher accuracy for detecting the ideal focus point. For observational light side astronomy, the Bahtinov mask allows quicker, more exact focusing when switching eyepieces. For imaging (dark side astronomy), where camera focusing is crucial to achieving the finest images, the Bahtinov mask makes it easy to find the point of optimal focus without having to guess and enables quick adjustments when switching filters or fine-tuning focus as your imaging session persists into the night.

The Astrozap Focusing Mask is proudly made in the United States from solid sheet aluminum, contrary to plastic focusing masks available from other manufacturers that are not anywhere near as durable. Powder coating helps maintain its appealing looks by preventing corrosion. AstroZap carries several sizes of focusing masks to fit telescopes with the most common outside diameters. Plastic screws mounted in rubber grommets are adjustable in order to conform to the exterior of the optical tube, keeping the screen in place while avoiding scratching or otherwise causing harm to the telescope's finish. The unique Bahtinov diffraction pattern utilized by this AstroZap Focusing Mask enables consistently optimal focus.

Completing your purchase

Take a moment to review your selection and total before payment.

Preparing your order

Please consider both preparation and transit when planning your purchase.

Standard Shipping: Handling (business days) 0–1; Transit (business days) 7–15.

Express Shipping: Handling (business days) 0–1; Transit (business days) 7–15.

View policy
Requesting a refund

Contact the store with your order details so your request can be reviewed.

Please contact us for the refund processing timeframe before returning an item.

View policy
Delivery arrangements

The available delivery services and charges are listed below.

Standard Shipping · United States: $0.00

Express Shipping · United States: $3.99

View policy
Before arranging a return

Speak with the store before arranging a return shipment.

United States · Return window (days after delivery): 30. Return method: By mail. Return postage: Seller pays.

View policy

Customer Reviews (4.8 / 5 · 5 reviews)

Eva ★★★★★

The aluminum frame feels solid and durable, and the diffraction pattern it produced was sharp and easy to read on my first try. I was able to dial in focus on a faint nebula in just a couple of minutes, which is a huge improvement over my old method.

Ruby D. ★★★★★

Swapping out the plastic focusing aid for this aluminum mask made a noticeable difference—it’s rigid and doesn’t flex when mounting. The diffraction spikes snapped into a sharp, clean pattern on my first test star, and the full-aperture design covers my scope perfectly.

William L. ★★★★★

Came with a perfect fit for my 4.5-inch refractor tube, and the rigid aluminum actually feels like it’ll last years of outdoor use. Dialing in focus on Jupiter’s moons was noticeably faster than my old paper mask.