{"product_id":"pegasus-astro-2inch-mounted-photographic-filter-ha-7nm","title":"Pegasus Astro 2inch mounted photographic filter - Ha 7nm","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003e7nm Narrowband H-alpha Filter\u003c\/li\u003e\n\u003cli\u003eGreater than 80% Transmission at 656nm\u003c\/li\u003e\n\u003cli\u003e1\/4 Wavefront Polish\u003c\/li\u003e\n\u003cli\u003eParfocal with Other Filters\u003c\/li\u003e\n\u003cli\u003eStandard 2-inch (M48x0.75) Mounting\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 - Ha 7nm\u003c\/h2\u003e\n\u003cp\u003eThis 2-inch mounted photographic Ha 7nm filter isolates the critical hydrogen-alpha emission line with a tight 7nm full width at half maximum (FWHM) bandpass centered at 656nm. With an average transmission rate over 80% and a 1\/4 wavefront polish, it captures high-contrast signal from emission nebulae while maintaining image sharpness. The filter glass is 2mm thick and housed in a standard M48x0.75 threaded cell for direct compatibility with 2-inch filter wheels and accessories.\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\u003eH-alpha Imaging at 7nm: Over 80% Transmission at 656nm\u003c\/h3\u003e\n\u003cp\u003eThe core of this filter is its ability to isolate the 656nm H-alpha line, the dominant wavelength emitted by star-forming regions like the Orion Nebula (M42) and North American Nebula (NGC 7000). By restricting the incoming light to a narrow 7nm window, it dramatically increases contrast by rejecting moonlight and light pollution from sodium and mercury vapor streetlights. The greater than 80% average transmission within this bandpass ensures that faint nebulosity is captured efficiently, reducing required exposure times compared to filters with lower transmission rates.\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\u003e1\/4 Wavefront Polish for Sharp, Parfocal Imaging\u003c\/h3\u003e\n\u003cp\u003eOptical quality is maintained by a 1\/4 wavefront polish across the filter's surface, preventing degradation of the image formed by your telescope. The filter is also specified as parfocal, meaning it is designed to maintain the same focal point as other filters of the same series. This minimizes the need to refocus when switching between LRGB and other narrowband filters, streamlining your imaging sequence and ensuring all data channels are equally sharp.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eMultilayer Anti-Reflection Coatings:\u003c\/strong\u003e Applied to the 2mm thick glass, these coatings suppress halos and internal reflections that can occur around bright stars, preserving contrast and detail in the surrounding nebulosity.\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStrict Optical Tolerances:\u003c\/strong\u003e The 1\/4 wave specification ensures that the filter will not introduce astigmatism or other aberrations, preserving the performance of your optical tube assembly (OTA).\n\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\u003e2-inch Mounted M48x0.75 Format with 2mm Glass\u003c\/h3\u003e\n\u003cp\u003eThis filter is housed in a standard 2-inch cell, which uses M48x0.75 threads for direct installation into any 2-inch filter wheel, filter drawer, or camera nosepiece. The total thickness of the mounted filter is 5mm, with the thread itself accounting for 2.5mm of that height. This low-profile design ensures compatibility with most imaging setups without introducing spacing or clearance issues. The glass substrate itself is 2mm thick, providing a rigid and stable optical element.\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\u003e7nm H-alpha vs. Broader and Narrower Bandpasses\u003c\/h3\u003e\n\u003cp\u003eChoosing a bandpass is a critical trade-off in astrophotography. A 7nm filter strikes a balance between performance and versatility, making it a common choice for a wide range of equipment and skies.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003evs. 12nm Filters:\u003c\/strong\u003e A 7nm filter provides significantly better contrast and light pollution rejection than a broader 12nm filter. This makes the 7nm a superior choice for imaging from suburban or moonlit skies. The trade-off is slightly dimmer stars, which can be beneficial for making the nebula the hero of the image.\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003evs. 3nm or 5nm Filters:\u003c\/strong\u003e Ultra-narrow filters (3nm\/5nm) offer the absolute highest contrast, ideal for heavily light-polluted areas or for separating fine details in bright nebulae. However, they are more demanding on your mount's guiding accuracy and can introduce halos on some optical systems. The 7nm bandpass is more forgiving and often a better starting point for those new to narrowband imaging.\n\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\"\u003eIs the 7nm Ha filter good for imaging from the city?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. The \u003cstrong\u003e7nm bandpass\u003c\/strong\u003e is extremely effective at blocking the most common sources of urban light pollution, such as sodium and mercury vapor streetlights, as well as natural skyglow and moonlight. This dramatically improves the signal-to-noise ratio, allowing you to capture faint emission nebulae even from heavily light-polluted locations.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat kind of objects is this 7nm Ha filter best for?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThis filter is designed specifically for \u003cstrong\u003eemission nebulae\u003c\/strong\u003e, which are rich in ionized hydrogen gas. Prime targets include the Orion Nebula (M42), the Lagoon Nebula (M8), the North American Nebula (NGC 7000), and the Veil Nebula complex in Cygnus. It is not suitable for broadband targets like galaxies or reflection nebulae.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill I need to refocus my 8\" f\/10 SCT when I switch to this 7nm Ha filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThis filter is designed to be \u003cstrong\u003eparfocal\u003c\/strong\u003e. This means that when used with other parfocal filters (typically from the same manufacturer), there should be minimal to no focus shift. For an f\/10 system like an SCT, any focus change will likely be too small to notice, saving you time during an imaging session.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow does the 7nm Ha filter affect star sizes?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eBecause the 7nm bandpass is so restrictive, it significantly reduces the brightness of stars, which emit light across the entire spectrum. This is often seen as a benefit, as it creates smaller, tighter stars in the final image and allows the faint structure of the nebula to stand out more prominently.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eCan I use this 7nm Ha filter with my color astronomy camera?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, you can. Using a narrowband filter like this with a One-Shot-Color (OSC) camera is a popular technique. Since the H-alpha light at 656nm will only pass through the red pixels of your camera's Bayer matrix, you will get a high-contrast monochrome image. This H-alpha data can then be blended with a standard color image of the same object to enhance the detail and \"pop\" of the red nebulosity.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill the M48x0.75 threads on this 7nm Ha filter fit my camera's 2-inch nosepiece?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes. The \u003cstrong\u003eM48x0.75 thread pitch\u003c\/strong\u003e is the standard for 2-inch astronomy filters. It is designed to thread directly into the base of any standard 2-inch eyepiece or camera nosepiece, as well as dedicated 2-inch filter wheels and filter drawers.\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 H-alpha\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\u003eCentral Wavelength\u003c\/td\u003e\n\u003ctd\u003e656 nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTransmission\u003c\/td\u003e\n\u003ctd\u003e\u0026gt;80% Average\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter Size\u003c\/td\u003e\n\u003ctd\u003e2 inch\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 Quality\u003c\/td\u003e\n\u003ctd\u003e1\/4 wavefront polish\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\u003e2 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTotal Mounted Thickness\u003c\/td\u003e\n\u003ctd\u003e5 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eThread Height\u003c\/td\u003e\n\u003ctd\u003e2.5 mm\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 Ha 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 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":52686359855389,"sku":"PEG-FLTR-2M-Ha","price":246.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/pegasus-astro-2inch-mounted-photographic-filter-ha-7nm-1_a9f0beef-4bd3-478b-8c25-5b3e846932dd.png?v=1793650768","url":"https:\/\/davidastro.com\/fr-int\/products\/pegasus-astro-2inch-mounted-photographic-filter-ha-7nm","provider":"David Astro","version":"1.0","type":"link"}