dew prevention

Astrozap AstroCap Focusing Caps

Astrozap   ——   SKU: AST-AZ-402
$32.57 CAD
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Product Info


About the AstroZap AstroCap Focusing Cap...

Every observer (light side) and imager (dark side) knows that sharp focus is essential for getting the most out of precious telescope time. Recently, the Bahtinov-style mask has overtaken the Hartmann mask in popularity for the reason that the Bahtinov diffraction pattern's unique display provides a more accurate guide to determining the optimum focus point. For light side astronomy, the Bahtinov mask enables faster, more precise focusing when changing eyepieces. For dark side astronomy, where camera focusing is critical to obtaining the best images, the Bahtinov mask eliminates the guesswork in locating the point of best focus and permits quick adjustment when changing filters or tweaking focus as the imaging run continues through the night.

Enter the Astrozap Focusing Caps...

Astrozap's unique Focusing Cap designs fit most telescopes and performs a dual function. The cap itself contains three holes at a calculated points around the perimeter of the cap. When the center knob is rotated, the inside panel lines up with the holes to create the Bahtinov pattern that admits starlight, creating the unmistakable Bahtinov diffraction spikes that enable determination of the best focus point. Turn the center knob again, and the inside panel rotates, closes the holes, and converts the focusing cap into a dust cap. All Astrozap Focusing Caps are proudly made in the USA out of solid aluminum, and powder coated to resist corrosion and retain their handsome appearance for years to come. As one imager discovered, it is good to have an Astrozap Focusing Cap handy because one never knows when the electric focuser will quit.


AstroZap AstroCap Focusing Cap - Features... 

  • The sizes listed below refer to the outside diameter of the telescope or dew shield that the Bahtinov mask will attach to.  Measure carefully before choosing the proper size for your telescope.
  • Achieve perfect focus with the Astrozap Astrocap with integrated Bahtinov Focusing Wheel!


  • The Astrozap AstroCap also functions as cover for your dew shield or optical tube assembly when wheels are closed.


  • Open the Astrocap focusing wheels with the turn of a thumbscrew when you are ready to focus an image.


  • Close the wheels when you wish to image dark frames with your CCD camera.


  • The Astrozap AstroCap is made of aluminum, and no tools are required!