The Celestron Off-Axis Guider uses a prism to intercept a small portion of the telescope’s focal plane (outside the field of view of the main imaging camera) to locate a guide star.
Any movement seen by the guide star will be the exact same movement seen by the imaging camera.
Guiding this way will correct for tracking errors, as well as opto-mechanical errors or flexure. The result: better astroimages with pinpoint round stars.
The Off-Axis Guider is an essential astro-imaging accessory for long focal length telescopes that require the most accurate guiding possible.
Off-Axis Guiders have been around for a long time, but typically pose three main challenges:
- Finding a guide star from the far edges of the telescope’s focal plane can be difficult, considering the small field of view and sometimes less-than-ideal illumination.
- Getting both imaging camera and autoguider to reach focus with one another is time consuming and sometimes requires experimentation.
- Additional spacers and adapters are usually required for your particular camera, telescope, and autoguider, which adds to cost and complexity.
Celestron’s Off-Axis Guider addresses these challenges by:
- Providing a large 12.5mm prism that can be adjusted to move closer to the center of the telescope’s focal plane, depending on the size of the imaging camera. This results in brighter guide stars, with the help of the large prism to fully illuminate the autoguider sensor.
- Featuring a high-quality, fixed-orientation Helical focuser. This provides extremely smooth and accurate focus of the autoguider without changing (or twisting) the autoguider camera orientation.
- Including all the needed spacers and adapters are included for most common imaging configurations, including DSLR cameras, Nightscape CCD cameras, and more. The following adapters are included: SCT/EdgeHD, female M48, female M42 (T-thread), male M48, male M42 (T-thread), 3 T-thread spacers
- Helical Focuser Travel: 8mm
- Telescope Connection: M42 T-thread, M48, and SCT/EdgeHD
- Autoguider Connection: M42 T-thread, and standard 1.25″ adapter
- Camera Connection: M42 T-thread, and M48
- Most accurate way to guide – improved accuracy compared to using a separate guide scope.
- 12.5mm multi-coated prism with aluminized backing for maximum reflectivity and illumination to the autoguider
- Fixed-orientation helical focuser for easy, smooth and accurate autoguider focus
- 48mm clear aperture supports full frame cameras without vignetting
- Includes adapters with the correct spacing for DSLR cameras, Nightscape CCD and other popular astroimaging cameras
- Ideal for Schmidt- Cassegrain and EdgeHD telescopes
Weight (oz):18 oz (510 g)
Clear Aperture (mm): 48mm mm (1.89 in)
Please Note: The optimum photographic back focus of the EdgeHD 8” when used with #94242 Reducer Lens at f/7 is 105 mm (please note, the back focus distance for Edge 8″ without the reducer is 133mm)
Our #93648 Off-Axis Guider, when used with the reducer #94242 and a DSLR, reaches appx 120mm (other imaging equipment may vary, please carefully work out your distances prior to purchase)
Therefore because the 105mm distance is so critical, the Off-Axis Guider is not typically compatible for use with a DSLR, EdgeHD 8″ and Reducer lens
The EdgeHD 11″ and 14″ all keep the same 146mm back focus with or without the reducer so are not affected.