{"product_id":"pegasus-astro-2inch-mounted-photographic-filter-s2-7nm","title":"Pegasus Astro 2inch mounted photographic filter - S2 7nm","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eIsolates the Sulfur-II emission line at 672nm\u003c\/li\u003e\n\u003cli\u003e7nm FWHM bandpass for high-contrast imaging\u003c\/li\u003e\n\u003cli\u003eTransmission greater than 80% at the target wavelength\u003c\/li\u003e\n\u003cli\u003eParfocal design minimizes refocusing when switching filters\u003c\/li\u003e\n\u003cli\u003eStandard 2-inch mounted format with M48 x 0.75 threads\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\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\u003e2-inch Mounted Photographic Filter - S2 7nm\u003c\/h2\u003e\n\u003cp\u003eThis 2-inch mounted S2 filter isolates the 672nm emission line with a tight 7nm FWHM bandpass, delivering over 80% peak transmission to capture faint, ionized sulfur structures in deep-sky nebulae. Its 1\/4 wavefront polished, 2mm thick glass substrate ensures sharp stars, while the parfocal design maintains focus when used alongside other narrowband filters in your wheel. The standard M48 x 0.75 thread fits all common 2-inch filter wheels and accessories for immediate integration into your imaging train.\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\u003eIsolating Sulfur-II: The 7nm Bandpass at 672nm\u003c\/h3\u003e\n\u003cp\u003eThe core of this filter is its ability to reject all light except for a narrow 7nm window centered on the 672nm wavelength. This is the spectral line for singly ionized sulfur (S-II), a key component in many emission nebulae like the Eagle Nebula (M16) and the Rosette Nebula (NGC 2244). By isolating this signal, the filter dramatically increases contrast, revealing delicate structures that are normally lost in the glare of starlight and light pollution.\u003c\/p\u003e\n\u003cp\u003eWith a peak transmission of over 80%, this filter efficiently passes the faint S-II signal to your camera sensor. This efficiency is critical for reducing exposure times and improving the signal-to-noise ratio in your final data, allowing you to pull out more detail from the faintest regions of your target.\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\u003eOptical Precision: 1\/4 Wavefront Polish and Parfocal Design\u003c\/h3\u003e\n\u003cp\u003eTo prevent image degradation, the 2mm thick optical glass is polished to a 1\/4 wavefront standard across its surface. This level of precision ensures that the filter will not introduce distortions or soften star images, preserving the resolution of your telescope. The filter's parfocal design means it shares a common focal point with other filters of the same series, eliminating the need for significant refocusing when sequencing different narrowband exposures.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e1\/4 Wavefront Polish:\u003c\/strong\u003e Guarantees that the filter maintains the sharpness and optical quality of your telescope system.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eParfocal Design:\u003c\/strong\u003e Saves critical imaging time by minimizing focus shifts when you switch between S-II, H-alpha, and O-III filters during an automated session.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-bg-light\"\u003e\n\u003cdiv class=\"DAV-section\"\u003e\n\u003ch3\u003eBuilt for Modern Imaging: 2-inch M48 Cell and AR Coatings\u003c\/h3\u003e\n\u003cp\u003eThe filter is housed in a durable 2-inch cell with standard M48 x 0.75 threads, ensuring compatibility with virtually all 2-inch filter wheels, drawers, and camera nosepieces. The surfaces of the filter are treated with a multilayer anti-reflection coating. This coating suppresses halos and internal reflections that can occur around bright stars, resulting in cleaner data with higher contrast and darker sky backgrounds.\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\u003eS-II in Context: Completing the Hubble Palette with H-alpha \u0026amp; O-III\u003c\/h3\u003e\n\u003cp\u003eWhile powerful on its own, this S2 7nm filter is most often used as part of a narrowband trio with Hydrogen-alpha (H-alpha) and Oxygen-III (O-III) filters. This combination allows you to create full-color images in the \"Hubble Palette,\" mapping S-II, H-alpha, and O-III data to the red, green, and blue channels, respectively. This technique produces dramatic, scientifically valuable images that reveal the detailed chemical composition and structure of nebulae.\u003c\/p\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 types of celestial objects are best for this S2 7nm filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThis filter is designed specifically for emission nebulae that are rich in ionized sulfur. It excels on targets like the Eagle Nebula (M16), the Omega Nebula (M17), and the Lagoon Nebula (M8), where it reveals intricate details in star-forming regions that are often invisible in broadband images.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the 7nm bandpass on this S2 filter help with light pollution?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe extremely narrow 7nm bandpass blocks out a vast majority of the visible spectrum, including common sources of light pollution like sodium and mercury-vapor streetlights. This allows you to capture clean, high-contrast images of emission nebulae even from suburban or city locations.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eIs this 2-inch S2 7nm filter parfocal with other filters?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, it is designed to be \u003cstrong\u003eparfocal\u003c\/strong\u003e. This means that if you are using it in a filter wheel with other parfocal H-alpha and O-III filters, you should not need to make significant focus adjustments when switching between them. This is a crucial feature for automated and remote imaging sessions.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use this S2 7nm filter for visual observing?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, this is not recommended. Narrowband filters like this one pass such a tiny fraction of the visible spectrum that the resulting image is far too dim for the human eye to see. This filter is designed exclusively for long-exposure astrophotography with monochrome cameras.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat does the M48 x 0.75 thread on this 2-inch filter mean for compatibility?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe M48 x 0.75 thread is the standard for 2-inch astronomy filters. It ensures this filter will screw directly into any 2-inch filter wheel, filter drawer, or accessory that accepts 2-inch filters. It is the largest standard thread before moving to larger, specialized filter sizes.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow would this S2 filter perform on the Heart Nebula (IC 1805) with a monochrome camera and an f\/5 refractor?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Heart Nebula is an excellent target for this filter. The S-II signal is prominent in the outer regions and central structures. With an f\/5 refractor and a sensitive monochrome camera, the filter's \u0026gt;80% transmission and 7nm bandpass would allow you to capture deep, high-contrast S-II data to complement your H-alpha and O-III exposures for a full Hubble Palette image.\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\u003eFilter Type\u003c\/td\u003e\n\u003ctd\u003eNarrowband (7nm)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCentral Wavelength\u003c\/td\u003e\n\u003ctd\u003e672 nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBandpass (FWHM)\u003c\/td\u003e\n\u003ctd\u003e7nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePeak Transmission\u003c\/td\u003e\n\u003ctd\u003e\u0026gt;80%\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSize\u003c\/td\u003e\n\u003ctd\u003e2 inch (mounted)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eThreads\u003c\/td\u003e\n\u003ctd\u003eM48 x 0.75\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Polish\u003c\/td\u003e\n\u003ctd\u003e1\/4 wavefront\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eParfocal\u003c\/td\u003e\n\u003ctd\u003eYes\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCoatings\u003c\/td\u003e\n\u003ctd\u003eMultilayer Anti-reflection\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eGlass Thickness\u003c\/td\u003e\n\u003ctd\u003e2mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTotal Cell Thickness\u003c\/td\u003e\n\u003ctd\u003e5mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eThread Height\u003c\/td\u003e\n\u003ctd\u003e2.5mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eShape\u003c\/td\u003e\n\u003ctd\u003eRound\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\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003e2-inch Mounted S2 7nm Filter\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eProtective Storage Case\u003c\/p\u003e\n\u003cp class=\"DAV-item-subtitle\"\u003e× 1\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"https:\/\/davidastro.com\/pages\/pegasus-astro-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003ePegasus Astro 2-Year Warranty\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Pegasus Astro","offers":[{"title":"Default Title","offer_id":52686360936733,"sku":"PEG-FLTR-2M-S2","price":344.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/pegasus-astro-2inch-mounted-photographic-filter-s2-7nm-1_daf8e68a-4ad3-4d31-a9ed-0624313326b0.png?v=1793650768","url":"https:\/\/davidastro.com\/fr\/products\/pegasus-astro-2inch-mounted-photographic-filter-s2-7nm","provider":"David Astro","version":"1.0","type":"link"}