{"product_id":"explore-scientific-epwp7240ed-01","title":"Explore Scientific 72° ED 40mm Waterproof Eyepiece","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003e40mm Focal Length\u003c\/li\u003e\n\u003cli\u003e72° Apparent Field of View\u003c\/li\u003e\n\u003cli\u003e2-Inch Barrel Diameter\u003c\/li\u003e\n\u003cli\u003eExtra-Low Dispersion (ED) Glass\u003c\/li\u003e\n\u003cli\u003eWaterproof and Gas-Purged Construction\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- more --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli class=\"active\"\u003eDescription\u003c\/li\u003e\n\u003cli\u003eFAQ\u003c\/li\u003e\n\u003cli\u003eSpecifications\u003c\/li\u003e\n\u003cli\u003eIn the Box\u003c\/li\u003e\n\u003cli\u003eDownloads\u003c\/li\u003e\n\u003cli\u003eWarranty\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\u003cli class=\"active\"\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section-center\"\u003e\n\u003ch2\u003eExplore Scientific 72° ED 40mm Waterproof Eyepiece\u003c\/h2\u003e\n\u003cp\u003eThe Explore Scientific 72° ED 40mm Waterproof Eyepiece combines a massive 40mm focal length with an immersive 72° apparent field in a 2-inch barrel to deliver the widest possible true field of view in its series. This 40mm, 72° design is engineered to frame the largest deep-sky objects, leveraging its 2-inch format for expansive, low-magnification sweeps of the night sky.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eThe 72° Apparent Field: Framing the Largest Celestial Objects\u003c\/h3\u003e\n\u003cp\u003eWith a 40mm focal length and a 72° apparent field, this eyepiece is built for one purpose: maximizing your true field of view. It provides an immersive, \"spacewalk\" perspective that allows you to take in entire star fields and vast deep-sky objects like the Andromeda Galaxy (M31) or the North American Nebula (NGC 7000) in a single, well-framed view. For owners of long focal-length telescopes like Schmidt-Cassegrains or Maksutovs, this eyepiece serves as the ultimate finder and low-power scanning tool.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003e40mm of ED Glass: High-Contrast, Color-Pure Views\u003c\/h3\u003e\n\u003cp\u003eAt the low magnifications produced by a 40mm eyepiece, controlling chromatic aberration is critical for a clean image. This eyepiece uses Extra-Low Dispersion (ED) glass to minimize color fringing, ensuring bright stars resolve to sharp points without distracting purple or blue halos. This superior color correction results in a higher-contrast view with a dark sky background, making faint nebulosity and galactic structure easier to detect.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eWaterproof 2-Inch Design for All-Weather Observing\u003c\/h3\u003e\n\u003cp\u003eBuilt for real-world observing conditions, the eyepiece is fully waterproof and gas-purged. This construction prevents internal fogging during nights with heavy dew and protects the internal lens surfaces from dust and fungus over the long term. The robust 2-inch barrel provides a secure connection to your focuser, essential for supporting an eyepiece of this class.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eExplore Scientific 72° 40mm vs. TeleVue Panoptic 41mm: Field and Correction\u003c\/h3\u003e\n\u003cp\u003eWhen choosing a low-power, 2-inch eyepiece, a key comparison is with the TeleVue Panoptic 41mm. While both eyepieces aim to maximize the true field of view, they take different design approaches.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eTeleVue Panoptic 41mm Advantage:\u003c\/strong\u003e The Panoptic uses a 46mm field stop, the maximum physically possible in a 2-inch barrel. This gives it the largest possible true field of view, even though its apparent field is a narrower 68°. It is renowned for its exceptional edge-of-field correction, even in fast telescopes.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eExplore Scientific 72° 40mm Advantage:\u003c\/strong\u003e This eyepiece delivers a wider, more immersive 72° apparent field of view. For observers who prioritize the \"spacewalk\" feeling over the absolute maximum true field, the wider apparent field can provide a more engaging visual experience. The use of ED glass is also a specific design choice aimed at maximizing contrast and color purity.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat is the primary use for the Explore Scientific 72° ED 40mm eyepiece?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThis eyepiece is designed for \u003cstrong\u003elow-magnification, wide-field observing\u003c\/strong\u003e. Its main purpose is to act as a \"finder\" eyepiece for locating objects and for viewing very large celestial targets like the entire Veil Nebula complex, the Andromeda Galaxy (M31), or sweeping through the Milky Way's star clouds.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow will the 72° ED 40mm eyepiece perform in my 8-inch f\/10 SCT?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eIt's an excellent match. In a typical 8\" f\/10 SCT with a 2000mm focal length, this eyepiece provides 50x magnification and a 4mm exit pupil, which is ideal for comfortable, bright views of deep-sky objects. It will deliver the widest possible true field of view your telescope can achieve, turning it into a capable instrument for scanning rich star fields.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs the 72° ED 40mm eyepiece a good choice for my f\/4.5 Dobsonian?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eIt can be, but there is a trade-off. In a fast f\/4.5 telescope, this 40mm eyepiece produces a very large 8.9mm exit pupil. Since the human eye can typically only dilate to about 7mm, some of the telescope's light-gathering capability will be lost. You may also see the shadow of your telescope's secondary mirror in the center of the view. It is generally better suited for telescopes of f\/6 or slower.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat does \"waterproof\" mean for an eyepiece like the 72° ED 40mm?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eA waterproof eyepiece is sealed with O-rings and purged with an inert gas (like argon or nitrogen). This has two key benefits:\n\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eIt prevents moisture from getting inside the eyepiece on dewy nights, stopping internal fogging.\u003c\/li\u003e\n\u003cli\u003eIt keeps dust, pollen, and fungus from contaminating the internal lens elements, ensuring a lifetime of clear views.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy would I choose the 72° ED 40mm eyepiece over a 32mm Plössl?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eWhile a 32mm Plössl is an excellent 1.25-inch eyepiece that also provides a wide true field, the \u003cstrong\u003eExplore Scientific 72° ED 40mm\u003c\/strong\u003e operates in a different class. It uses a 2-inch barrel to provide an even wider true field of view, lower magnification, and a more immersive 72° apparent field compared to the Plössl's ~50°. The ED glass also provides superior color correction.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use filters with the Explore Scientific 72° ED 40mm eyepiece?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. The 2-inch barrel is threaded to accept standard 2-inch (48mm) astronomy filters. This eyepiece is an excellent candidate for use with nebula filters like an O-III or UHC filter when observing targets like the Orion Nebula (M42) or the Lagoon Nebula (M8), as the low magnification and bright image help offset the dimming effect of the filter.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ctable class=\"DAV-specifications\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocal Length\u003c\/td\u003e\n\u003ctd\u003e40mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eApparent Field of View\u003c\/td\u003e\n\u003ctd\u003e72°\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBarrel Size\u003c\/td\u003e\n\u003ctd\u003e2-inch\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eLens Elements\u003c\/td\u003e\n\u003ctd\u003eExtra-Low Dispersion (ED) Glass\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eConstruction\u003c\/td\u003e\n\u003ctd\u003eWaterproof, Gas-Purged\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cul class=\"DAV-grid\"\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/explore-scientific-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eExplore Scientific Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Explore Scientific","offers":[{"title":"Default Title","offer_id":52909340000541,"sku":"ES-EPWP7240ED-01","price":630.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/ExploreScientific-72-ED-Series-40mm-Waterproof-Eyepiece-1_6b083fee-1c99-4b34-8c00-8c8eb5180814.jpg?v=1789061321","url":"https:\/\/davidastro.com\/fr\/products\/explore-scientific-epwp7240ed-01","provider":"David Astro","version":"1.0","type":"link"}