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$Focusing cap with built-in Bahtinov focusing mask for 80mm refractors and similar scopes$ $Focusing cap with built-in Bahtinov focusing mask for 80mm refractors and similar scopes$ $Focusing cap with built-in Bahtinov focusing mask for 80mm refractors and similar scopes$ $Focusing cap with built-in Bahtinov focusing mask for 80mm refractors and similar scopes$ $Focusing cap with built-in Bahtinov focusing mask for 80mm refractors and similar scopes$

$Focusing cap with built-in Bahtinov focusing mask for 80mm refractors and similar scopes$

$Images showing how the Bahtinov mask changes a star's diffraction pattern as the focus changes.$

Image showing a typical Astrozap focusing mask with the Bahtinov wheel in the closed (dust cover function) position.

Image showing a typical Astrozap focusing mask with the Bahtinov wheel in the open (focusing) position.

Close-up of the foam-lined rim and one of the nylon screws that hold the focusing mask in place on your scope and allow it to fit a range of scope sizes.

Astrozap Focusing cap with built-in Bahtinov focusing mask for 80mm refractors and similar scopes

3 Review(s) | Add Your Review

$77.00

Availability: More on the way

This Astrozap Bahtinov mask focusing cap fits most 80mm refractors, such as the Astro-Tech AT80EDT, or any scope with an optical tube outer diameter between 101mm and 110mm . . .

Our Product #: FC80AZ

Astrozap Product #: AZ-403

Product Description

This Astrozap focusing cap with built-in Bahtinov focusing mask will fit most 80mm aperture fast focal ratio ED refractors, such as the Astro-Tech AT80EDT ED triplet apo, or any scope with an optical tube or lens shade measuring between approximately 101mm (4") and 110mm (4.3") in outer diameter. Check your optical tube diameter for certain before ordering.

The inside of the focusing cap is lined with soft foam to protect the finish on your scope or lens shade. Three nylon thumbscrews tighten onto your scope's front cell or lens shade to hold the focusing cap in place and allow the cap to fit the above range of scope diameters. When not used for focusing, the Bahtinov wheel can be closed as shown below allowing the focusing cap to be used as a dust cap for your scope.

The feature image below will show you a star's appearance in a Takahashi Epsilon 180 reflector as seen through the Bahtinov Mask. The difference in the focuser position between the almost-in-focus images and the sharply focused image shown below is very small, only a few tenths of a millimeter, showing the sensitivity of the Bahtinov focusing method.

Tech Details

Warranty	1 year

Reviews

Review by: Matthew

I use this with my ED 80 and love it. Much faster and more precise feeling way to focus. (Posted on 1/13/2019)

Review by: Nimitz

Let’s face it, if you cn’t achieve perfect focus, there really is no point to trying to do the rest of AP. This Bahtinov mask is the gold standard for achieving perfect manl focus every time, whether your using a DSLR or CMOS. This fits perfectly over my 81mm APO & integrated cover is a nice plus. Just find a bright star & adjust focus until the center diffraction spike is exactly in the middle of the “X’” and you’re at perfect focus! Brilliant . (Posted on 1/5/2019)

Review by: cevoner

I use AstroZap on my Orion 80ED CF telescope to focus on stars before I attempt a fine focus. It works well on this telescope. Ia dded tape to quickly remove the mask before I check through my eyepiece. (Posted on 11/14/2018)

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