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Shelyak 0.63x SCT F/6.3 Focal Reducer
The Shelyak 0.63x SCT F/6.3 Focal Reducer converts a standard f/10 Schmidt-Cassegrain telescope into a faster f/6.3 instrument, specifically for spectroscopy. This 0.63x reduction is achieved with a anti-reflection coated apochromatic triplet. It attaches via a standard 2-inch (50.8 mm) rear cell thread, making it compatible with most Meade and Celestron SCTs.
An Apochromatic Triplet for F/6.3 Spectroscopy
Transforming your telescope from f/10 to f/6.3 is critical for efficient spectroscopy. The faster focal ratio concentrates the star's light more intensely onto the narrow slit of a spectrograph like the Alpy 600 or UVEX, dramatically improving signal-to-noise ratio and reducing exposure times on faint targets.
This unit employs an apochromatic triplet design. This ensures that different wavelengths of light are brought to a single, sharp focal point before entering the spectrograph, preventing chromatic aberration from contaminating your spectral data and ensuring maximum accuracy in your measurements.
2-inch SCT Threads for Meade and Celestron Telescopes
This reducer is engineered for seamless integration into the most common catadioptric setups. It features the standard 2-inch (50.8 mm) female thread found on the rear cell of virtually all modern Schmidt-Cassegrain telescopes from Celestron and Meade.
The output side of the reducer is threaded to accept accessories like the Shelyak variable T-adapter (BA0027), allowing you to achieve precise back focus for your specific instrument. This direct-thread system creates a rigid, flexure-free connection between your telescope and spectrograph, which is essential for maintaining alignment throughout a long observation session.
Made for Low-Resolution Spectroscopes
Shelyak designed this reducer to bring an F/10 Schmidt-Cassegrain to F/6.3 for its low-resolution spectroscopes.
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Suited instruments: the Alpy 600, UVEX, Star'Ex LR and the eShel injection unit (FIGU).
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Optics: an anti-reflection coated apochromatic triplet. The variable T-adapter (BA0027) fits directly onto it.
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Why do I need the Shelyak 0.63x reducer for spectroscopy with my SCT?
A standard f/10 SCT produces a small, dim image at the focal plane. The Shelyak 0.63x reducer converts this to f/6.3, creating a brighter, more concentrated beam of light. This allows more photons to pass through the narrow slit of your spectrograph per unit of time, significantly boosting your signal and allowing you to capture spectra of fainter objects.
What makes this Shelyak reducer different from a standard Celestron or Meade f/6.3 reducer?
Shelyak builds it as an anti-reflection coated apochromatic triplet and intends it for low-resolution spectroscopes such as the Alpy 600, UVEX, Star'Ex LR and the eShel injection unit (FIGU). The variable T-adapter (BA0027) fits directly onto it.
Will this 0.63x reducer work with my 8" Celestron SCT and an Alpy 600 spectroscope?
Yes, this is an ideal combination. The reducer will thread directly onto the 2-inch rear cell of your 8" SCT. Shelyak names the Alpy 600 among the low-resolution spectroscopes that F/6.3 suits better than F/10.
How do I attach the Shelyak 0.63x reducer to my telescope and spectrograph?
The reducer has female 2-inch SCT threads. You simply unthread your existing visual back or camera adapter from your telescope's rear cell and thread the reducer on in its place. The output side of the reducer has male threads that connect to other accessories, such as the Shelyak variable T-adapter (BA0027), which then connects to your spectrograph.
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| Reduction Factor |
0.63x |
| Resulting Focal Ratio |
f/6.3 (from f/10) |
| Optical Design |
Apochromatic Triplet |
| Coatings |
Anti-reflective |
| Telescope Connection |
2-inch (50.8 mm) SCT Female Thread |
| Compatibility |
Most Meade & Celestron SCTs |
| Camera-side connection |
2-inch SCT Male Thread |
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0.63x SCT F/6.3 Focal Reducer
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Shelyak 1-Year Warranty
