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Starizona Nexus 0.75x Newtonian Focal Reducer/Coma Corrector
Starizona Nexus 0.75x Newtonian Focal Reducer/Coma Corrector
Starizona Nexus 0.75x Newtonian Focal Reducer/Coma Corrector

Starizona Nexus 0.75x Newtonian Focal Reducer/Coma Corrector

by Starizona
SKU STZ-NEXUS-075
$449.00 USD - $449.00 USD
$449.00 USD
$449.00 USD - $449.00 USD
$449.00 USD
Price Match Policy!
  • Focal Reduction: 0.75x
  • Corrected Image Circle: 28mm (APS-C Format)
  • Required Backfocus: 55mm
  • Barrel Size: 2"
  • Camera Connection: M48 x 0.75 Threads
  • Filter Threads: M48 (2")
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  • Description
  • FAQ
  • Specifications
  • Warranty

  • Starizona Nexus 0.75x Newtonian Focal Reducer/Coma Corrector

    The Starizona Nexus 0.75x Newtonian Focal Reducer/Coma Corrector transforms your Newtonian into a dedicated astrograph, delivering both a wider field and sharper stars from edge to edge across its 28mm image circle. This dual-purpose optic provides a 0.75x focal reduction while correcting coma, fitting into any standard 2" focuser and maintaining the common 55mm backfocus distance for modern cameras.

    0.75x Reduction: Transform Your f/4 Newtonian into an f/3 Astrograph

    Most coma correctors maintain a telescope's native focal ratio. The Starizona Nexus accelerates it. The 0.75x reduction factor converts a standard f/4 imaging Newtonian into a faster f/3 system, widening your field of view and gathering light 1.8 times faster. This significant reduction in exposure time allows you to capture more data on faint nebulae and galaxies in a single night.

    A 28mm Coma-Free Image Circle for APS-C Sensors

    Engineered with extra-low dispersion (ED) glass, the Nexus delivers a flat, coma-free field across a 28mm image circle. This is perfectly matched to the APS-C sensors found in many popular DSLR, mirrorless, and dedicated astronomy cameras, ensuring pinpoint stars across the entire frame without vignetting. The optical design provides professional-grade correction for Newtonians as fast as f/3.

    Standard 55mm Backfocus and M48 Threads

    The Nexus integrates seamlessly into standard imaging trains. It requires 55mm of backfocus from the corrector's M48 x 0.75 male threads to your camera sensor, a distance compatible with DSLRs using a standard T-ring and most CMOS/CCD camera setups with extension tubes. The telescope side of the 2" barrel features M48 threads for mounting 2" filters, while a removable outer lip allows the unit to be seated deeper in the focuser or attached directly via optional threaded adapters.

    Understanding the Parfocal Design and 55mm Requirement

    The Nexus is designed to be parfocal, meaning it does not shift your telescope's native focal point. If your camera can achieve focus in your Newtonian without the Nexus, it will also reach focus with it. However, this comes with a critical caveat: the entire imaging train, including the Nexus, must maintain 55mm of spacing between the corrector and the sensor.

    This requirement is the primary limiting factor. While most f/4 Newtonians designed for imaging have ample backfocus, many visual Newtonians (often f/5 or slower) may not have enough inward focuser travel to accommodate a camera at the required 55mm distance. Always verify your telescope has sufficient backfocus before use.

    Starizona Nexus vs. Standard 1.0x Coma Correctors

    While a high-quality 1.0x coma corrector provides a larger corrected field and maintains your telescope's native image scale for maximum resolution on small targets, it does not reduce your exposure time. The Nexus offers a different set of advantages for wide-field imagers.

    • Choose a 1.0x Corrector for: Maximum image scale on galaxies and planetary nebulae; use with full-frame sensors that exceed the Nexus's 28mm image circle.
    • Choose the Starizona Nexus for: Capturing large nebulae, maximizing data acquisition speed with its 0.75x reduction, and turning an f/4 scope into a faster f/3 system.

  • What does the Starizona Nexus do for my f/4 Newtonian?

    The Starizona Nexus serves two functions: it corrects coma for sharp stars across the field and reduces the focal ratio by a factor of 0.75x. This makes your f/4 telescope an f/3 system, giving you a wider field of view and cutting your exposure times nearly in half (a 1.8x speed increase).

    Will the Starizona Nexus work with my full-frame camera?

    No, the Starizona Nexus is not recommended for full-frame sensors. It is designed to produce a corrected 28mm image circle, which is ideal for APS-C and smaller sensors. A full-frame sensor (typically 42-44mm diagonal) would show significant coma and vignetting in the corners.

    How do I achieve the 55mm backfocus with the Starizona Nexus?

    The 55mm distance is measured from the base of the M48 threads on the camera side of the Nexus to your camera's sensor. This is a standard distance for most imaging correctors. You can achieve it using a DSLR with a standard 48mm T-ring, or with a dedicated astronomy camera by using a combination of M48 extension rings to make up the required distance.

    Is the Starizona Nexus truly parfocal?

    Yes, in the sense that it doesn't change the telescope's focus position. However, it still requires 55mm of spacing between itself and the camera sensor. Many visual Newtonians lack the focuser in-travel to accommodate this 55mm distance, even though the corrector itself is parfocal. It is primarily designed for imaging Newtonians that have ample backfocus available.

    With an 8" f/4 imaging Newtonian, how will the Nexus change my images of the Andromeda Galaxy (M31)?

    An 8" (200mm) f/4 Newtonian has a focal length of 800mm. With the 0.75x Nexus, this becomes a 600mm f/3 system. This wider, faster configuration will allow you to frame the entirety of the Andromeda Galaxy (M31) and its companions M32 and M110 more easily on an APS-C sensor, while capturing the faint outer dust lanes with significantly shorter exposures.

    My 10" f/5 Dobsonian has limited backfocus. Can I use the Starizona Nexus for imaging?

    It is unlikely. Most visual telescopes like Dobsonians are not designed with the extra backfocus needed for photographic correctors. The Starizona Nexus requires your camera sensor to be placed 55mm behind it, and a typical Dobsonian focuser cannot rack in far enough to bring this configuration to focus. This corrector is intended for Newtonians built specifically for astrophotography.

  • Focal Reduction Factor 0.75x
    Corrected Image Circle 28mm (APS format)
    Required In-Focus Travel None (parfocal)*
    Backfocus from Corrector 55mm
    Camera Side Threads M48 x 0.75
    Telescope Side Filter Threads M48 (for 2" mounted filters)
    Barrel Size 2"
    Overall Length 3.14" (80mm)
    Weight 0.74 lbs (335g)
  • Starizona Warranty