The Celestron RASA 8" Rowe-Ackermann Schmidt Astrograph is an incredibly fast f/2 optical system designed for imaging with modern CMOS cameras. The RASA 8" provides a flat field free of optical aberrations across a 22mm field of view, with usable performance up to 32mm making it suitable for APS-C and smaller sized sensors. Note: the RASA 8" cannot be used with systems requiring filter wheels or large DSLR bodies. Instead, it is recommend to use colour or mono CMOS cameras with a filter drawer. As the focal plane is at the front of the optical system, it cannot be used visually with an eyepiece. As the RASA 8" is a fast f/2 system, you can use much shorter exposure times than usual to capture faint objects. This combined with the short focal length of 400mm means that you don't need to have super-accurate tracking over extended periods, making the RASA 8" suitable for use on a wide variety of equatorial mounts. The RASA 8" includes Celestron's Ultra-Stable Focus System which utilizes two sets of precision sealed ball bearings to virtually eliminate lateral movement of the primary mirror when focusing, slewing or tracking. Building on the legacy of Celestron's Schmidt Cameras of the 1970's, the RASA 8" allows astrophotographers to capture incredible data with minimal exposure times. The 4-element lens group with rare-earth ED glass provide images free from aberrations that are inherent in other types of telescopes. With an extended spectral range of 390-800nm, the RASA 8" is designed for use with modern cameras that are sensitive to NIR wavelengths in the 700-800nm range. Unlike many telescopes which are only designed for the visual spectrum up to 700nm, this extended range will be well focused in the RASA 8", leading to sharper and brighter images. The RASA 8" performs best once its optics have reached thermal equilibrium with the ambient air. To aid this, the telescope is equipped with cooling fans which direct air through the tube and around the primary mirror. Note: it is recommended to only use narrowband filters that are optimized for fast systems such as the Antlia ALP-T FAST or Baader Highspeed CMOS filters. Specifications Optical design Rowe-Ackermann Schmidt Astrograph Aperture 203 mm (8") Focal length 400 mm Focal ratio f/2.0 Resolving power 0.57 arc seconds Image circle 22 mm, 3.15° Usable field 32 mm, 4.6° with only minimal performance loss at edge of FOV Light gathering power 843 times the human eye Central obstruction diameter 93 mm (46% of aperture diameter) Wavelength range 390 - 800 nm Spot size < 4.6μm RMS across image circle Optical coatings StarBright XLT Off-axis illumination 93% at 11 mm off-axis Optical window diameter 46 mm Backfocus with included M42 adapter 25 mm Backfocus from top of threaded collar 29 mm Mount attachment CGE dovetail plate Focuser Ultra-Stable Focusing System Included connection adapters M42 x 0.75, C-mount Tube length 628 mm Tube weight 7.7 kg Tube diameter 235 mm SKU CE-91073 Items included RASA 8" CGE dovetail Dew cap M42 camera adapter C-thread adapter Fan battery pack Filter solutions Due to the very short backfocus of 29mm from the threaded collar, we recommend the Baader UFC filter drawer system for ZWO ASI cameras. or the FCCT filter drawer/tilt adjuster for QHY cameras. Usage with Baader UFC In order to connect ZWO ASI cameras with 6.5mm of backfocus such as the 533, 183 and 294 series, you will need the following pieces: UFC Base Chamber S70 - BA2459110 UFC M42 ASI adapter - BA2459170 UFC RASA 8" adapter - BA2459136 UFC filter slider - BA2459112 Usage with Baader FCCT In order to connect QHY cameras with a 90mm body diameter such as the 268M (pre-June 2023 revision), 294 or 533, you will need the following pieces: FCCT II filter changer - BA2459071 FCCT filter holder Downloads Celestron RASA 8" manual
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