Pentax 70509 Eyepiece Review

Pentax 70509 Eyepiece for PF80EDA Spotting Scope – Unparalleled Clarity and Versatility


  • Pentax PF-100ED, PF-80EDA, PF-80ED, PR-80EDA, PR-65EDA, PF-65ED(A)II spotting scopes

Optical Performance

  • Apparent angle of view 38-60°
  • Long 18/22mm eye relief accommodates eyewear
  • Magnification: 26-78x with 100mm scope, 21-63x/20-60x/20-61x with 80mm scopes, 16-46x/16-48x with 65mm scopes

Construction Details

  • USA Standard 1.25″ eyepiece threading diameter
  • Waterproof & fogproof (JIS Class 4-rated)
  • Multi-layer coated optics
  • High-refraction, low dispersion lanthanum glass
  • Accepts conventional 1.25″ diameter filters for astronomical and terrestrial applications

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The world of birdwatching, wildlife observation, and long-distance target spotting requires precision optics to truly appreciate the beauty and detail of distant subjects. As an avid nature enthusiast and amateur ornithologist, I’ve spent countless hours in the field, searching for the perfect eyepiece to pair with my Pentax PF80EDA spotting scope. After extensive research and testing, I finally settled on the Pentax 70509 eyepiece, and I must say it has truly transformed my outdoor experiences. In this comprehensive review, I will walk you through the various aspects of this eyepiece and why it has become an invaluable addition to my kit.

Optical Performance (5/5)

The primary reason for investing in a quality eyepiece is to enhance the optical performance of your spotting scope, and the Pentax 70509 excels in this regard. It offers remarkable clarity, brightness, and color fidelity. With its 20-60x zoom range, it provides a versatile viewing experience, allowing me to switch between wide-angle scans and detailed close-ups effortlessly.

The image quality is consistently sharp across the entire zoom range, which is a testament to Pentax’s commitment to precision engineering. Whether I’m observing a distant eagle perched high in a tree or identifying tiny warblers flitting among the branches, the Pentax 70509 delivers crisp, high-contrast images with minimal chromatic aberration. This level of optical quality greatly enhances the overall birdwatching and wildlife observation experience, making it easier to identify and appreciate the finer details of each subject.

One aspect I particularly appreciate is the generous eye relief, which is vital for extended viewing sessions. It accommodates eyeglass wearers like myself comfortably, allowing us to enjoy the full field of view without straining our eyes. The eyepiece’s large 1.25-inch eyepiece barrel diameter also facilitates comfortable viewing, especially during prolonged observations.

Build Quality and Durability (5/5)

The Pentax 70509 eyepiece is a testament to Pentax’s reputation for crafting durable and reliable optical equipment. From the moment I held it in my hands, I could sense its solid construction. The eyepiece feels robust and is built to withstand the rigors of outdoor adventures. It’s sealed and nitrogen-filled, making it both waterproof and fog-proof, ensuring it can perform flawlessly in various weather conditions. I’ve used it in rain, fog, and even light snow, and it has never let me down.

The eyepiece’s rubber-armored body not only provides excellent grip but also adds an extra layer of protection. It’s designed to absorb shocks and protect against accidental drops, which is crucial for anyone who spends time in the field. Even after several accidental bumps against tree branches and rocks, the eyepiece has shown no signs of wear or damage.

The focus ring on the eyepiece is smooth and precise, allowing for fine adjustments to achieve the perfect focus. Additionally, the zoom ring operates smoothly, with distinct stops at various magnifications, making it easy to set the desired zoom level quickly.

Ease of Use and Versatility (5/5)

One of the standout features of the Pentax 70509 eyepiece is its user-friendliness. Swapping eyepieces on my PF80EDA is a breeze, thanks to the twist-lock mechanism. It securely attaches to the spotting scope without any wobble or play, ensuring that the optical alignment remains intact even during rough handling. This quick and secure attachment is a game-changer when you’re in the field, allowing you to switch eyepieces effortlessly to adapt to different observing conditions.

The eyepiece’s zooming mechanism is equally straightforward to use. The zoom ring is conveniently located and easy to grip, allowing for smooth zooming with just a single hand. This is essential when you need to quickly adjust magnification to follow a bird in flight or track wildlife on the move.

The built-in eyecup is adjustable, accommodating various users’ preferences and helping to block out stray light. It’s a small but thoughtful feature that adds to the overall comfort and usability of the eyepiece.

Field Performance (5/5)

I’ve had the pleasure of using the Pentax 70509 eyepiece in a wide range of field conditions, and it has consistently delivered exceptional performance. The 20-60x zoom range is perfectly suited for birdwatching, wildlife observation, and even amateur astronomy.

At lower magnifications, I can quickly scan large areas to locate distant subjects, making it easier to spot birds or animals that are well-camouflaged or hidden among vegetation. The wide field of view at 20x allows for immersive landscape observations, which is fantastic for capturing the broader context of the natural world.

When I need to get up close and personal, I simply zoom in, and the Pentax 70509 transitions seamlessly to higher magnifications. Even at 60x, the image remains sharp and detailed, allowing me to scrutinize even the tiniest details on birds’ plumage or wildlife behavior from a safe distance. This versatility has made the eyepiece an invaluable tool for my outdoor adventures.

Another noteworthy feature is the eyepiece’s ability to maintain image quality even in low-light conditions. Whether it’s dawn, dusk, or a cloudy day, the Pentax 70509 consistently delivers bright and clear images, thanks in part to its large objective lens and premium glass elements. This has allowed me to extend my observation hours and capture breathtaking moments during the golden hours of wildlife activity.

Value for Money (4/5)

While the Pentax 70509 eyepiece is undeniably an investment, it offers outstanding value for money when you consider its optical performance, build quality, and versatility. Quality optics are not cheap, and Pentax has managed to strike a balance between affordability and performance with this eyepiece.

Compared to some other high-end eyepieces on the market, the Pentax 70509 offers similar or even better optical quality at a more reasonable price point. Its durable construction means it will serve you well for many years, making it a worthwhile investment for serious birdwatchers, wildlife enthusiasts, and amateur astronomers.

However, it’s worth noting that the eyepiece’s price point might be a bit steep for those who are just getting started in birdwatching or outdoor observation. If you’re a casual observer, there are more budget-friendly options available that can provide decent performance. Nonetheless, for those who are passionate about the hobby and demand top-notch performance, the Pentax 70509 is a wise choice that will not disappoint.


In conclusion, the Pentax 70509 eyepiece for the PF80EDA spotting scope is a remarkable optical accessory that has significantly enhanced my outdoor experiences. Its exceptional optical performance, solid build quality, ease of use, and versatility make it a top choice for birdwatchers, wildlife enthusiasts, and amateur astronomers alike.

This eyepiece has become an indispensable part of my kit, allowing me to explore the natural world with unparalleled clarity and precision. Whether I’m observing rare bird species, tracking elusive wildlife, or stargazing under the night sky, the Pentax 70509 consistently delivers breathtaking views and enriching experiences.

While it may be on the higher end of the price spectrum, the investment is well worth it for those who are serious about their outdoor pursuits. Its durability ensures that it will serve you faithfully for many seasons to come, making it a valuable addition to any nature enthusiast’s gear collection.

In my opinion, the Pentax 70509 eyepiece is not just a piece of optical equipment; it’s a gateway to a deeper connection with the natural world, allowing you to appreciate its beauty and intricacies like never before. If you’re looking to elevate your outdoor observations and capture stunning moments in the wild, this eyepiece is the perfect companion for your Pentax PF80EDA spotting scope.