Choosing the right secondary mirror for your telescope is a nuanced process that combines science, precision, and a deep understanding of your astronomical goals. Whether you’re an amateur stargazer or a dedicated astro-photographer, the secondary mirror plays a pivotal role in your telescope’s optical system, affecting everything from image clarity to light throughput. In this comprehensive guide, we’ll explore how to select the perfect secondary mirror, with a special focus on the offerings from Antares Optics, a trusted name in the astronomy community for high-quality optical components.


Understanding Secondary Mirrors

Secondary mirrors are crucial in many telescope designs, particularly in reflectors and compound telescopes, where they serve to redirect light from the primary mirror to the eyepiece or imaging sensor. The quality, size, and shape of the secondary mirror significantly impact the telescope’s overall performance, affecting image brightness, contrast, and sharpness.


Factors to Consider

When selecting a secondary mirror, consider several key factors:


  • Optical Compatibility: The secondary mirror must match the optical design of your telescope. This includes the curvature (flat for Newtonians, curved for Schmidt-Cassegrains and Ritchey-Chrétiens) and the size, which should complement the primary mirror without unnecessarily obstructing light.
  • Material and Coating: High-quality materials like borosilicate glass or fused silica, combined with enhanced coatings (e.g., aluminum or silver), ensure high reflectivity and durability.
  • Wavefront Accuracy: The precision of the mirror’s surface, often expressed in fractions of a wavelength (e.g., λ/4, λ/10), dictates how accurately it can redirect light to the focal point without introducing aberrations.


Antares Optics: A Closer Look

Antares Optics is renowned for its extensive range of secondary mirrors, catering to various telescope designs and requirements. Their offerings include:

  • Minor Axis Sizes: From compact 1.25″ mirrors suitable for small reflectors to larger 4.0″ mirrors for advanced astro-imaging setups, ensuring compatibility with a wide array of telescope apertures.
  • Wavefront Precision: Antares mirrors are available in multiple precision grades, such as 1/12 wave, 1/20 wave, and even up to 1/30 wave, catering to the needs of both amateur hobbyists and serious researchers seeking the utmost in image clarity.
  • Material Choices: With substrates like low-expansion borosilicate glass and fused silica, Antares mirrors provide stability and minimal thermal distortion, crucial for consistent observational quality over varying temperatures.
  • Coating Options: Reflectivity is key for optimal light transmission. Antares mirrors come with high-quality coatings, ensuring excellent light reflection across the visible spectrum and into the infrared, crucial for deep-sky imaging.


Selecting the Right Mirror

When choosing a secondary mirror from Antares Optics, consider your telescope’s primary mirror size and focal ratio to determine the appropriate secondary size. A larger secondary mirror may be necessary for telescopes with very short focal ratios to fully illuminate the field of view, but it’s important to balance this with the potential for increased light obstruction.


For those engaged in astrophotography or detailed planetary observation, opting for a secondary mirror with a higher wavefront accuracy can significantly enhance image quality. Antares’ high-precision mirrors, such as those offering 1/30 wave precision, provide exceptional clarity and detail, crucial for capturing subtle celestial features.


Practical Considerations

Installation and alignment are critical. A secondary mirror must be precisely aligned with the primary to achieve optimal performance. Tools and techniques for collimation vary, but the process is essential for ensuring that your telescope delivers the best possible images.


Durability and maintenance should also influence your choice. Mirrors with robust coatings are more resistant to degradation over time, maintaining their reflectivity and optical quality even after years of use. Antares Optics mirrors, known for their durable coatings and high-quality substrates, stand up well to the rigors of regular observation and cleaning.



The selection of a secondary mirror is a critical step in optimizing your telescope for the wonders of the night sky. By considering factors such as optical design, material quality, and wavefront accuracy, and by choosing a reputable supplier like Antares Optics, you can significantly enhance your astronomical observations and imaging. Antares’ commitment to quality and variety ensures that astronomers of all levels can find the perfect secondary mirror to meet their needs, unlocking the full potential of their telescopic equipment. With the right secondary mirror, the universe’s most intricate details come into sharper focus, revealing the beauty and complexity of the cosmos like never before.