Cameras

QHY off-axis guider coupled with Minicam 8

Tuesday, July 15, 2025

Astrophotographers often strive to balance complexity and performance, and the QHY off-axis guider coupled with Minicam 8 offers a seamless solution, making it easier for enthusiasts to elevate their imaging setups without adding unnecessary weight or complication to their rigs.

Dylan O’Donnell recently took an in-depth look at the new QHY Off-Axis Guider (OAG), highlighting its performance, installation, and impact on his astrophotography workflow (like him, I love OAG too). Working from the Byron Bay Observatory, Dylan operates two primary telescope setups: a formidable Celestron 14-inch Edge HD on an EQ8 RH Pro mount and a highly portable Apertura 75Q paired with the QHY MiniCam 8. The larger rig demands its own dedicated structure due to its size and weight, while the smaller system has been built with portability, simplicity, and convenience in mind.

QHY off-axis guider coupled with Minicam 8

The QHY MiniCam 8, mounted on the Apertura 75Q, is a small-sensor camera that delivers impressive astrophotography results. It comes equipped with its own eight-position filter wheel, offering versatility for multi-band imaging without constant manual changes. Originally, this setup also included a second guide scope, but the introduction of the compact QHY Off-Axis Guider allowed Dylan to eliminate the extra guide scope, simplifying the system while maintaining guiding precision.

Off-axis guiding works by diverting a small portion of light from the main image path using a tiny prism. This light is sent at a right angle to a dedicated guide camera, which continuously monitors the position of guide stars to correct for tracking errors during long exposures. Dylan has long favored off-axis guiding on his larger telescope, where guiding accuracy is critical for sharp images, but integrating it into the smaller, portable rig brought a touch of luxury and an overall reduction in system complexity.

The installation process for the QHY Off-Axis Guider proved to be straightforward, following a series of methodical steps. First, Dylan removed the top screws on the frame, avoiding the bottom ones, and then attached the guider using the included long screws. A piece of tape on the prism was taken off, the thumb screw was loosened, and the prism was lifted out of the way. The compression ring was adjusted carefully, using the tool provided instead of fingers to ensure proper alignment. After repositioning the prism, the guide camera was installed, ensuring its sensor aligned perfectly with the prism. Thumb screws secured the camera in place, and extension rings were added as necessary to achieve the correct backfocus. Finally, the assembled camera and guider were reattached to the telescope, completing the integration.

Once installed, the first task was achieving focus on the main telescope. This required removing about 20 millimeters of extension, a routine adjustment given the specific optical path of the Apertura 75Q. After focusing the main tube, attention turned to the guide camera, which was slid in and out to achieve optimal focus on the guiding chip. This process went smoothly, and once completed, the setup was ready for field testing.

Observing a dense region of the Milky Way provided a wealth of guide stars, filling the guide camera’s field of view even at short exposures of two to three seconds. This abundance of stars made it effortless to lock onto a suitable guide point, ensuring the mount could track celestial targets with precision. While wide-field systems like the Apertura 75Q are generally forgiving when it comes to guiding, meaning they don’t demand sub-arcsecond accuracy, the addition of the OAG offered seamless replacement of the secondary guide scope and streamlined the setup significantly.

It’s worth noting that the MiniCam 8’s small sensor creates a field of view that feels zoomed in, adding to the challenge and satisfaction of obtaining sharp, well-guided images. However, Dylan observed no dramatic improvement in guiding performance with the OAG compared to the prior configuration, largely because the Star Adventurer GTi mount used in this portable rig was already operating at its payload limits. This particular mount, which Dylan received as a prototype from Sky-Watcher before its main production run, performs admirably but reaches its threshold with the current setup. He hinted at an upcoming upgrade to the mount that promises to resolve these limitations and improve overall performance.

Testing under a full moon presented additional challenges, as the bright lunar light washed out much of the available color data, limiting the quality of RGB imaging. Despite these conditions, Dylan managed to capture a usable image in just 46 minutes of integration time, demonstrating the reliability and convenience of the OAG. He noted that while the mount remains the weak point of the system, the combination of the Apertura 75Q, the MiniCam 8, and the QHY Off-Axis Guider works impressively well together.

A notable observation from Dylan’s experience is the design difference between the QHY Off-Axis Guider models. The Mini OAG designed for small rigs features a surprisingly large prism, providing greater flexibility in guide camera selection and making it easier to hit the ideal focus point. This contrasts with larger OAG models like the OAGM, which have smaller prisms despite being intended for bigger telescopes. The large prism on the Mini OAG proved advantageous, delivering an ample selection of guide stars and simplifying the guiding process.

While guiding improvements were subtle, the greatest benefit came in the form of reduced hardware complexity and improved system balance. By eliminating the separate guide scope, the setup became lighter and more streamlined, important factors for portable astrophotography where every ounce matters. Additionally, Dylan emphasized that the QHY Off-Axis Guider is an affordable accessory, making it a compelling upgrade for anyone already using the QHY MiniCam 8. The guider integrates seamlessly into the image train, requires minimal effort to set up, and offers immediate practical benefits.

The results, even under challenging sky conditions, were promising. With only 46 minutes of exposure time and a bright full moon overhead, Dylan was able to process the captured data into a satisfactory image. While it wasn’t the best possible photograph the rig could deliver, it effectively demonstrated the OAG’s role in maintaining stable guiding and image sharpness.

Dylan also made it clear that this was not a sponsored review. Although QHY provided the Off-Axis Guider unit for testing, they allowed him to keep it, and he expressed genuine appreciation for that. He openly shared that he intends to leave the guider permanently installed on his setup because of how well it complements his existing gear. For astrophotographers looking to simplify their rigs or enhance guiding accuracy without breaking the bank, the QHY Off-Axis Guider stands out as an excellent option.

Fully Integrated - QHY Off-Axis Guider (OAG)

NGC 6334 is a massive emission nebula and star-forming region located in the constellation Scorpius. It is colloquially known as the Cat's Paw Nebula, and can be found 3° to the west-northwest of the bright star Lambda Scorpii.