{"product_id":"celestron-8-rowe-ackermann-schmidt-astrograph-optical-tube-assembly-91073","title":"Celestron 8\" Rowe-Ackermann Schmidt Astrograph Optical Tube Assembly - 91073","description":"\u003ch3 style=\"text-align: center;\"\u003eCelestron 8\" Rowe-Ackermann Schmidt Astrograph \u003cbr\u003e Optical Tube Assembly\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eFlat image field free of optical aberrations like field curvature, coma, astigmatism, and chromatic aberration across an entire APS-C sensor\u003c\/li\u003e\n\u003cli\u003eNEW Ultra-Stable Focus System – six precision sealed ball bearings virtually eliminate image shift\u003c\/li\u003e\n\u003cli\u003eIntegrated air cooling system –12V DC MagLev fan reduces cooldown time and provides optimal air flow while filtering out dust\u003c\/li\u003e\n\u003cli\u003eInternal filter mount – seamlessly accommodates a Light Pollution Imaging Filter into the optical path\u003c\/li\u003e\n\u003cli\u003eCGE dovetail mounting rail\u003c\/li\u003e\n\u003cli\u003ePerforms over a wider spectral range than most telescopes, from 390-800 nm, so more of the light passing through the astrograph is in sharp focus\u003c\/li\u003e\n\u003cli\u003eWider spectral range means brighter image results with your digital camera\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eThe 8\" Rowe-Ackermann Schmidt Astrograph (RASA) from Celestron, is a cost-effective optical system for wide field astroimaging. It offers unprecedented value in aperture, speed, field of view, and optical performance. The RASA design has a convenient external prime-focus image capture location with a flat focal plane, providing small spot sizes to the edge of a wide field. The result is images that are free of optical defects like field curvature, off-axis coma, or astigmatism. RASA 8\" has an ample back-focus distance of 25 mm which accommodates a wide variety of imaging sensors.\u003c\/p\u003e\n\u003cp\u003eSome Information About the RASA Technology:\u003c\/p\u003e\n\u003cp\u003eCelestron's 8\" Rowe-Ackermann Schmidt Astrograph (RASA’s) optical design is patented (US 2016\/0299331 A1). The design consists of a Schmidt corrector, spherical primary mirror, lens group, and optical window. The lens group contains 4 elements and utilizes rare-earth elements. Unlike many telescopes that only perform well over the visible spectrum (400 nm-700 nm), the 8” RASA’s optics are designed to perform over a wider spectral range, from 390 nm-800 nm. This allows more of the light emitted from the astronomical object to be sharply focused in the image. Also better spectral matching to silicon array sensors.\u003c\/p\u003e\n\u003cp\u003eWith many imaging systems, adding an extra piece of flat glass such as a filter may not affect the optical performance. However, that is not the case with super-fast optical systems like the RASA. Celestron's engineers addressed this concern by designing the RASA with a removeable optical window. This means you can maintain peak optical performance if a filter is added or if a camera has its own optical window. Simply remove the flat window and replace it with a Celestron filter. Celestron offers a Light Pollution Imaging Filter designed specifically for the 8” RASA, which replaces that optical window.\u003c\/p\u003e\n\u003cp\u003eAll refractive optical surfaces are coated with StarBright XLT coatings, while the primary mirror uses enhanced aluminum coatings. This maintains high light transmission through the entire optical system. When compared with a “Hyperstar SCT” system, the RASA 8 provides better optical performance and field illumination.\u003c\/p\u003e\n\u003cp\u003e8\" Astrograph Scope Description:\u003c\/p\u003e\n\u003cp\u003eCapture spectacular wide-field deep sky images in seconds with Celestron’s new portable astrograph, the 8” Rowe-Ackermann Schmidt Astrograph (RASA). This incredibly fast f\/2.0 system is the perfect companion to today’s color astronomical CMOS cameras, smaller CCD cameras, and mirrorless cameras. Thanks to its fast focal ratio and patented optical design, you can produce sharp, detailed images and often, you can eliminate the need for using an autoguider completely because of the fast exposures. Weighing in at just 17 pounds, it’s easy to transport your 8” RASA from Celestron to the most remote dark sky locations.\u003c\/p\u003e\n\u003cp\u003eThe 8” RASA is an imaging telescope that delivers a flat field without optical aberrations for razor sharp stars across a wide field of view. This astrograph can capture stunning deep-sky astronomical images without the challenges typically presented by longer focal length instruments at a fraction of the cost of those systems. The latest addition to the RASA family, this 8” version has many of the same thoughtfully designed features as its “big brother” the RASA 11\", including the integrated air-cooling system, internal filter mount, and sturdy CGE dovetail mounting bar.\u003c\/p\u003e\n\u003cp\u003eAs a typical astrograph design, this scope was purely designed for imaging, hence the 8” RASA cannot be used visually. The prime focus focal plane is located near the front aperture of the optical system, so it cannot accommodate a traditional eyepiece. Since it is an F\/2.0 optical system, imagers can use shorter exposure times to capture detail in faint objects. With sensitive cameras and the proper “live stacking” software, the 8” RASA can provide an almost real-time observing experience. View images on a computer instantly that are brighter and more detailed than can be seen in much bigger telescopes with the naked eye.\u003c\/p\u003e\n\u003cp\u003eBecause shorter exposure times are possible, your equatorial mount won’t need to accurately track over extended periods. The 8” RASA’s relatively short 400 mm focal length also lessens the demand for equatorial tracking accuracy. In many cases, autoguiding will not be required. Weighing only 17 lb, this optical tube pairs perfectly with a wide variety of mounts. Celestron has unveiled a new focuser design that mitigates lateral movement of the primary mirror when focusing, slewing, or tracking with the astrograph. Focusing is easier, more accurate, and more stable than ever. This Ultra-Stable Focus System uses two sets of precision bearings that are precisely aligned and tested during the assembly process to ensure optimal focus results.\u003c\/p\u003e\n\u003cp\u003eNote that the 8” model RASA was designed with color astronomical CMOS cameras, smaller CCD cameras, and mirrorless cameras in mind. The telescope does not work with standard DSLR cameras. It is optimized for sensors which have up to a 22 mm diagonal, but performs well with sensors up to 32 mm in diagonal. The APS-C sized sensors used in many mirrorless cameras are a good choice. 42 mm full frame sensors will also work, but performance will be poor at the edges of the sensor and field illumination will be reduced. Additionally, it is not recommended to pair RASA 8 with any camera body more than 4” in diameter. See the chart below to determine if your camera is compatible with RASA 8.\u003c\/p\u003e\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eCamera\u003c\/td\u003e\n\u003ctd\u003eCompatible with RASA 8?\u003c\/td\u003e\n\u003ctd\u003eAdapter required\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eAstronomical CMOS\/CCD camera with C-mount\u003c\/td\u003e\n\u003ctd\u003eYes\u003c\/td\u003e\n\u003ctd\u003eC-mount adapter (included)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAstronomical CMOS\/CCD camera with M42-thread mount\u003c\/td\u003e\n\u003ctd\u003eYes\u003c\/td\u003e\n\u003ctd\u003eM42 adapter (included) with M42 extension tubes (not included)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAstronomical CMOS\/CCD camera with other mount\u003c\/td\u003e\n\u003ctd\u003eYes\u003c\/td\u003e\n\u003ctd\u003eCustom camera adapter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCanon mirrorless with APS-C sensor\u003c\/td\u003e\n\u003ctd\u003eYes\u003c\/td\u003e\n\u003ctd\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCanon mirrorless adapter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e(sold separately)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSony mirrorless with APS-C sensor\u003c\/td\u003e\n\u003ctd\u003eYes\u003c\/td\u003e\n\u003ctd\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSony mirrorless adapter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e(sold separately)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCanon mirrorless with full frame (42mm) sensor\u003c\/td\u003e\n\u003ctd\u003eYes, but not optimized across the full sensor\u003c\/td\u003e\n\u003ctd\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCanon mirrorless adapter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e(sold separately)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSony mirrorless with full frame (42mm) sensor\u003c\/td\u003e\n\u003ctd\u003eYes, but not optimized across the full sensor\u003c\/td\u003e\n\u003ctd\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSony mirrorless adapter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e(sold separately)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDSLR\u003c\/td\u003e\n\u003ctd\u003eNo\u003c\/td\u003e\n\u003ctd\u003e--\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003ch3 style=\"text-align: center;\"\u003eSpecifications:\u003c\/h3\u003e\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Design\u003c\/td\u003e\n\u003ctd\u003eRowe-Ackermann Schmidt Astrograph (RASA)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAperture\u003c\/td\u003e\n\u003ctd\u003e203 mm (8\")\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocal Length\u003c\/td\u003e\n\u003ctd\u003e400 mm (15.74\")\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocal Ratio\u003c\/td\u003e\n\u003ctd\u003ef\/2.0\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCentral obstruction diameter\u003c\/td\u003e\n\u003ctd\u003e93 mm (3.66\") (46% of aperture diameter)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eLight Gathering Power (Compared to human eye)\u003c\/td\u003e\n\u003ctd\u003e843X\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eResolution (Rayleigh)\u003c\/td\u003e\n\u003ctd\u003e0.68 arcsecond\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eResolution (Dawes)\u003c\/td\u003e\n\u003ctd\u003e0.57 arcsecond\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eImage circle\u003c\/td\u003e\n\u003ctd\u003e22 mm (.86\") Ø, 3.15°\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eUseable field\u003c\/td\u003e\n\u003ctd\u003e32 mm (1.26\") Ø, 4.6°, only minimal performance loss at edge\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWavelength range\u003c\/td\u003e\n\u003ctd\u003e390 nm – 800 nm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpot size\u003c\/td\u003e\n\u003ctd\u003e\u0026lt; 4.6 μm RMS across image circle\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical coatings\u003c\/td\u003e\n\u003ctd\u003eXLT multi-coatings used throughout\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOff-axis Illumination\u003c\/td\u003e\n\u003ctd\u003e93% at 11 mm (0.43\") off-axis\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical window\u003c\/td\u003e\n\u003ctd\u003e46 mm (1.81\") Ø\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBack focus with included camera adapter\u003c\/td\u003e\n\u003ctd\u003e25 mm (0.98\")\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBack focus from top of threaded collar\u003c\/td\u003e\n\u003ctd\u003e29 mm (1.14\")\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Tube\u003c\/td\u003e\n\u003ctd\u003eAluminum\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Tube Dims.\u003c\/td\u003e\n\u003ctd\u003e628 mm (24.7\") length | 235 mm (9.3\") diameter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFocuser\u003c\/td\u003e\n\u003ctd\u003eNew focuser design, minimizes focus shift\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFinderscope\u003c\/td\u003e\n\u003ctd\u003eNot included\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOptical Tube Weight\u003c\/td\u003e\n\u003ctd\u003e17 lb (7.7 kg)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOther features\u003c\/td\u003e\n\u003ctd\u003eVentilation fan, built in filter mount\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eIncluded items\u003c\/td\u003e\n\u003ctd\u003eM42 camera adapter, C-Thread camera adapter, fan battery pack\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDovetail Mount\u003c\/td\u003e\n\u003ctd\u003eCGE Dovetail Bar\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e","brand":"Celestron","offers":[{"title":"Default Title","offer_id":19436632440945,"sku":"CEL-91073","price":1973.95,"currency_code":"EUR","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0851\/2766\/products\/91073_8in_Rowe-Ackermann_Schmidt_Astrograph_01_570x380_2x_09fd6c14-fcef-4b00-9601-e8da6ad53a0a.jpg?v=1776459290","url":"https:\/\/khanscope.com\/en-fr\/products\/celestron-8-rowe-ackermann-schmidt-astrograph-optical-tube-assembly-91073","provider":"Khan Scope Centre","version":"1.0","type":"link"}