Celestron Off-Axis GuiderItem#: HN-CELE597
The Off-Axis Guider is an essential astroimaging accessory for long focal length telescopes that require the most accurate guiding possible. 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.
Off-Axis Guiders have been around for a long time, but typically pose three main challenges:
1. 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.
2. Getting both imaging camera and autoguider to reach focus with one another is time consuming and sometimes requires experimentation.
3. 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:
1. 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.
2. 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.
3. 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
The Off-Axis Guider (OAG) requires a telescope, imaging camera, autoguider, and a mount tracking equatorially with autoguiding capability. You should already be familiar with these items before using the Off-Axis Guider.
To attach the front of the OAG to the telescope, the telescope must have M42 T-threads, M48 threads, or 2" Schmidt-Cassegrain style threads. If your telescope has a 2" visual back, you will need to provide a camera adapter to attach the telescope to the Off-Axis Guider. Camera adapters are commonly available that adapt from 2" to M42 T-Thread (also called T2).
Note that because the OAG comsumes a significant amount of inward focus travel, some telescopes will not be able to reach focus with this accessory. Most Newtonian reflectors and some Refractors do not have enough inward focus travel to accommodate the Off-Axis Guider. Refractors designed for astroimaging typically have plenty of focus travel, as do most catadioptric telescopes such as the Schmidt-Cassegrain or EdgeHD.
You may need to configure the OAG to your particular telescope, camera, and autoguider combination. The measurements listed below refer to the actual length the part consumers when installed on the telescope..
- OAG Body: 29mm
- SCT Adapter: 25.3mm
- Male M42 and M48 camera adapters: 12.5mm
- Female M42 and M48 telescope adapters: 4.5mm
- Short T-Thread Spacer Ring: 6mm
- Medium T-Thread Spacer Ring: 11.55mm
- Long T-Thread Spacer Ring: 24.25mm
- Medium M48 Spacer Ring: 11.55mm
A CCD camera or specialized astroimaging camera should have female T-threads or 48mm threads. It will attach to one of the two camera adapters included with the OAG.
DSLR cameras require a T-ring specific to the make and model of the camera. Canon and Nikon T-rings are available from Celestron. Full frame DSLR cameras should use a wide T-ring with 48mm threads to fully illuminate the sensor's field of view.
Dimensions & Specifications
Telescope Accessories Series
Celestron Photographic / Visual Accessories
DocumentationDownload the Celestron Off-Axis Guider User Manual
- Industry-acclaimed Sony EXview HAD ICX618ALA monochrome CCD sensor
- High-speed USB 3.0 connection provides fastest possible frame rate (also backwards compatible with USB 2.0)
- Downloads up to 120 frames per second, acquiring more data in less time
- Capable of exposures faster than 1/100th of a second
- 12-bit image output provides superior dynamic range
- 5 Mega Pixel Color Sensor
- View and capture live video on your computer
- 1.25" Barrel format
- Barrel accepts 1.25" eyepiece filters
- Camera control software included
- Equivalent to approx 5mm telescope eyepiece
- Reduce vibration and dampening time with these pads
- Place under each tripod leg for suppressed vibration
- Helpful when viewing on patio's or decks
- Great for viewing at extremely high magnifications