{"product_id":"askar-3nm-colour-magic-ultra-ha-oiii-e1-filter-2","title":"Askar 3nm Colour Magic Ultra Ha\/OIII E1 Filter - 2\"","description":"\u003cul class=\"DAV-feature-list\"\u003e\n\u003cli\u003eDual-bandpass for Hydrogen-alpha (656.6nm) and Oxygen-III (500.7nm)\u003c\/li\u003e\n\u003cli\u003eUltra-narrow 3.7nm (Ha) and 4.0nm (OIII) FWHM bandwidths\u003c\/li\u003e\n\u003cli\u003e85% peak transmittance at both center wavelengths\u003c\/li\u003e\n\u003cli\u003e≥OD5 blocking from 200-1100nm to suppress star halos\u003c\/li\u003e\n\u003cli\u003e2-inch mounted format with 1.85mm glass thickness\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\u003eAskar 3nm Colour Magic Ultra Ha\/OIII E1 Filter - 2\"\u003c\/h2\u003e\n\u003cp\u003eThe Askar 3nm Colour Magic Ultra E1 filter isolates critical nebulae emission lines with its ultra-narrow 3.7nm Hydrogen-alpha and 4.0nm Oxygen-III bandpasses. It achieves a peak transmittance of 85% at both the 656.6nm and 500.7nm center wavelengths, maximizing signal capture from emission targets. With off-band blocking rated at ≥OD5 from 200-1100nm, this filter delivers exceptionally high-contrast images by suppressing light pollution, moonlight, and unwanted starlight.\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\u003eDual-Bandpass Imaging with 85% Peak Transmittance\u003c\/h3\u003e\n\u003cp\u003eDesigned for one-shot color cameras, the Ultra E1 captures the two most important emission lines simultaneously, drastically reducing total imaging time. By passing light at both 656.6nm (Ha) and 500.7nm (OIII) with 85% efficiency, you gather data for both the red and blue-green structures of targets like the Veil Nebula or the Rosette Nebula (NGC 2237) in a single set of exposures. This dual-band approach streamlines your workflow without compromising signal strength.\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\u003e3.7nm \u0026amp; 4.0nm Bandwidths for Extreme Light Pollution Rejection\u003c\/h3\u003e\n\u003cp\u003eThe defining feature of this filter is its extremely narrow full-width at half-maximum (FWHM). The 3.7nm band for Ha and 4.0nm for OIII aggressively reject unwanted light, including severe urban light pollution and natural skyglow. This surgical isolation of the nebula's signal creates a jet-black sky background, making faint, wispy details pop with dramatic contrast even from city backyards.\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\u003eOD5 Blocking and 30\" Parallelism for Halo-Free Stars\u003c\/h3\u003e\n\u003cp\u003eOptical precision extends beyond the passbands. The filter provides ≥OD5 blocking across the wide 200-1100nm spectrum, ensuring that stray UV and IR light, which can cause halos on bright stars, never reaches the sensor. A parallelism of 30 arcseconds guarantees the filter will not introduce distortions or degrade the sharpness of your optical system, maintaining pinpoint stars across the field of view.\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\u003eAskar 3nm Ultra vs. Wider Dual-Band Filters: Contrast and Star Size\u003c\/h3\u003e\n\u003cp\u003eCompared to filters with 7nm or wider bandpasses, the Askar 3nm Ultra E1 offers a significant advantage in signal-to-noise ratio under light-polluted skies. The trade-off for this extreme contrast is a slight reduction in star brightness and potentially longer sub-exposure times to achieve the same signal level.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eAskar 3nm Ultra E1:\u003c\/strong\u003e Delivers maximum nebula contrast by eliminating more background light. It is the superior choice for imaging from Bortle 7-9 locations or during bright moon phases.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWider Dual-Band Filters:\u003c\/strong\u003e Capture signal faster and often produce smaller, more natural-looking stars, as very narrow filters can sometimes slightly bloat the brightest stars due to diffraction effects. They are excellent for dark sky sites where light pollution is less of a concern.\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 Askar 3nm Ultra E1 filter effective in Bortle 8 or 9 skies?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, absolutely. The ultra-narrow 3.7nm and 4.0nm bandwidths are specifically designed for this purpose. The Askar Ultra E1 excels at isolating the specific wavelengths of light from emission nebulae while aggressively blocking the broad-spectrum glow from city lights, making it one of the most effective tools for imaging from heavily light-polluted areas.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eHow will the Askar 3nm Ultra E1 filter perform on the Trifid Nebula (M20) with my f\/7 refractor?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThe Askar Ultra E1 is an excellent choice for the Trifid Nebula (M20). It will cleanly separate the red hydrogen-alpha emission region from the blue-green oxygen-III structures with a one-shot color camera. In an f\/7 system, you won't have issues with band-shifting, and the filter's high 85% transmittance will help capture good signal despite the slower focal ratio.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhy are the bandwidths for the Askar Ultra E1 filter different for Ha (3.7nm) and OIII (4.0nm)?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eThis is a deliberate optical design choice. The OIII emission line is often fainter than Ha in many nebulae, so providing a slightly wider 4.0nm bandpass allows more OIII signal to be collected, helping to balance the final color image. The Ha line is typically stronger, so a tighter 3.7nm band can be used for maximum contrast without sacrificing too much signal.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eDo I need a monochrome camera to use the Askar 3nm Ultra E1 filter?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eNo, this filter is specifically designed for use with \u003cstrong\u003eone-shot color (OSC) cameras\u003c\/strong\u003e. It passes both red (Ha) and blue-green (OIII) light simultaneously, which are then captured by the corresponding pixels on your color sensor to create a rich color image with minimal processing effort.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWhat does the ≥OD5 blocking specification mean for my images?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003e\u003cstrong\u003eOD5 (Optical Density 5)\u003c\/strong\u003e means the filter blocks at least 99.999% of unwanted light outside its designated passbands. For astrophotography, this is critical for preventing halos around bright stars, which are often caused by out-of-focus UV and Infrared light that your telescope's optics were not designed to correct. This deep blocking ensures clean, high-contrast results.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion\"\u003e\n\u003ch3 class=\"DAV-accordion-Q\"\u003eWill this 2\" Askar Ultra E1 filter work with a full-frame sensor?\u003c\/h3\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"DAV-accordion-A\"\u003e\n\u003cp\u003eYes, the 2-inch mounted format is designed to be large enough to fully illuminate full-frame sensors (36mm x 24mm) without vignetting, assuming it is placed correctly in the optical train, such as in a filter drawer or wheel close to the sensor.\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\u003eFWHM (Full-Width Half-Maximum)\u003c\/td\u003e\n\u003ctd\u003eHa: 3.7nm ± 0.3nm \/ OIII: 4.0nm ± 0.3nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCenter Wavelength (CWL)\u003c\/td\u003e\n\u003ctd\u003e656.6nm (Ha) \u0026amp; 500.7nm (OIII)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePeak Transmittance\u003c\/td\u003e\n\u003ctd\u003e≥85%\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOff-Band Blocking\u003c\/td\u003e\n\u003ctd\u003e≥OD5 (Optical Density 5) @ 200-1100nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eGlass Thickness\u003c\/td\u003e\n\u003ctd\u003e1.85 ± 0.05mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSurface Finish\u003c\/td\u003e\n\u003ctd\u003e60\/40\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eParallelism\u003c\/td\u003e\n\u003ctd\u003e30 arcseconds\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\"\u003eAskar 3nm Colour Magic Ultra Ha\/OIII E1 Filter - 2\"\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\n\u003cul class=\"DAV-grid\"\u003e\n\u003cli class=\"DAV-grid-item\"\u003e\u003ca href=\"https:\/\/www.sharpstar-optics.com\/download_list_1\/7.html\" target=\"_blank\"\u003e\u003csvg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" viewbox=\"0 0 640 512\" class=\"DAV-img-box\"\u003e\u003cpath fill=\"#0047a7\" d=\"M128 32C92.7 32 64 60.7 64 96l0 256 64 0 0-256 384 0 0 256 64 0 0-256c0-35.3-28.7-64-64-64L128 32zM19.2 384C8.6 384 0 392.6 0 403.2C0 445.6 34.4 480 76.8 480l486.4 0c42.4 0 76.8-34.4 76.8-76.8c0-10.6-8.6-19.2-19.2-19.2L19.2 384z\"\u003e\u003c\/path\u003e\u003c\/svg\u003e \n\u003cdiv\u003e\n\u003cp class=\"DAV-item-title\"\u003eDownload Software \u0026amp; Drivers\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/davidastro.com\/pages\/askar-warranty-policy\" rel=\"noopener\" target=\"_blank\"\u003eAskar 1-Year Warranty\u003c\/a\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Askar","offers":[{"title":"Default Title","offer_id":50344440856861,"sku":"ASK-ASKAR2DBE1","price":605.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0753\/5280\/1565\/files\/Askar-Colour-Magic-E1-Filter.jpg?v=1757644549","url":"https:\/\/davidastro.com\/fr-us\/products\/askar-3nm-colour-magic-ultra-ha-oiii-e1-filter-2","provider":"David Astro","version":"1.0","type":"link"}