QHYCCD QHYOAG-M Pro Off-Axis Guider

A 14 x 10mm Prism for Large Guide Sensors

At the heart of the OAG-M Pro is an oversized 14 x 10mm prism, designed to fully illuminate the large sensors found on modern guide cameras like the QHY5III174M. This large clear aperture captures a wider patch of sky, dramatically increasing the number of available guide stars compared to OAGs with smaller prisms. This is especially critical in long focal length systems where the field of view is narrow and stars are sparse.

By providing an unvignetted field for your guide camera, the OAG-M Pro ensures you can leverage the full sensitivity and field of view of your guide sensor. The result is a better chance of finding a usable guide star at long focal lengths.

Rigid, Thin Profile: 12mm Back Focus & 6-Screw Mounting

Engineered for stability and minimal impact on your imaging train, the QHYOAG-M Pro has a slim body that uses only 12mm of back focus. This thin profile preserves precious back focus for use with filter wheels and other accessories. The telescope side uses M54/0.75 with the matching adapter; a 5mm M54 spacer is included.

For a completely rigid connection, the OAG-M Pro attaches directly to QHYCFW3L and QHYCFW3M filter wheels using a pattern of six 3mm through holes. This screwed connection gives a solid, parallel and reliable mechanical link between the guider, filter wheel and camera.

QHYOAG-M Pro vs. Standard OAGs: Finding Guide Stars at Long Focal Lengths

The primary advantage of the QHYOAG-M Pro over previous generations of off-axis guiders is its prism size. Many standard OAGs use a prism around 8x8mm, which can cause significant vignetting on guide cameras with larger sensors. When using a camera like the QHY5III174M with a small-prism OAG, the corners of the sensor are starved for light, effectively reducing your field of view and limiting your guide star options.

The OAG-M Pro's 14 x 10mm prism solves this problem by delivering a much larger illuminated field. In the same optical system, the difference is immediately apparent: where a smaller prism would produce a heavily vignetted image, the OAG-M Pro provides a bright, usable field across the entire guide sensor.

Precision Focus: 1.25-inch Helical Focuser with Lock

Achieving sharp focus with your guide camera is critical for accurate guiding. The QHYOAG-M Pro incorporates a 1.25-inch helical focuser that allows for fine, smooth focus adjustments. Once you've achieved a sharp star profile, a locking knob secures the focuser in place, preventing any drift during an imaging session.

• Prism Position Adjustment: A side-mounted locking knob allows you to adjust the prism's stalk position. If the prism shows in your main camera's image, loosen the knob and move the prism further away from the sensor.
• Parfocal Setup: To achieve focus, the distance from the prism to the guide camera sensor must equal the distance from the prism to the main imaging sensor. The helical focuser's range makes it easy to dial in this precise spacing for perfectly parfocal guiding and imaging.