An OAG, or off-axis guider, offers a better way to guide when used with longer focal length telescopes when compared to traditional guide scopes, which can add unwanted weight, balance and possible flexure issues. An OAG also lets you guide at the same focal length as your telescope. This is especially important to focal lengths beyond 1000mm. The ZWO OAG-L Off-Axis Guider has a large prism size of 12*12mm, far bigger than standard ZWO OAG's prism size of 8*8mm. The bigger clear aperture allows for a wider field of view. OAG-L Features Lightweight, with a thickness of 17.5mm A large 12*12mm prism Effective light-passing aperture is 11.7mm*8.3mm The OAG-L can be used to connect the main camera and guide camera simultaneously. No guide telescope required. The OAG-L comes with an M48 sensor tilt plate with a thickness of 5 mm The OAG-L is designed a bit differently than the now discontinued OAG-M68, should you be familiar with that model. On the OAG-L, the inner threads are removed so you can use the screws to directly connect to other equipment. A helical focuser is built into the OAG-L...there is no need to buy the ZWO 1.25" Helical Focuser separately. Please Note... When you are choosing a guide camera for the ZWO OAG-L, remember that it can only work with ASI Mini cameras like the ASI174MM Mini (best match for prism size), ASI290MM Mini and ASI120MM Mini. It is not compatible with other ZWO planetary cameras. When matching up your main imaging camera to the OAG-L, keep in mind that the large clear aperture of the OAG-L supports both APS-C and full-frame cameras without vignetting. You can also use it with a ZWO 2” EFW or 7x36mm EFW filter wheel. That said, if you have an imaging camera with a 4/3" or smaller sensor, you may want to consider buying the standard ZWO OAG instead. While your camera would work with the OAG-L, it would not be necessary. Additionally, ZWO recommends that you do not use the OAG-L with telescopes whose clear aperture is smaller than M48, again, in that case, the standard OAG would be your best bet. Matching the Sensor Tilt Plate to Your Telescope Threads... ZWO includes an M48 sensor tilt plate with the OAG-L, and so if the thread of your telescope side is M48, you are golden. However, if the thread of your telescope is larger than M48, such as M54 or M68, you will need to remove and replace it with the proper size sensor tilt plate to match the corresponding thread of your telescope. You can choose an M54 or M68 sensor tilt plate from the suggested accessories listed below if needed. Removing the M48 Sensor Tilt Plate... Finally, when adding OAG-L into your optical train, please make sure the prism won’t block the camera sensor. You can use the guiding screw to adjust the guiding camera’s focus length. Please make sure the distances from the prism to the main camera and to the guide camera are the same. To ensure the result, it is better to do this during the daytime as the adjustment will be very difficult at night. 1. Use an M2 hex wrench in the through hole of the sensor tilt plate to loosen the M4 screw. 2. Pinch the prism on both sides and then pull it to the proper position. 3. Re-tighten the M4 screw with the M2 hex wrench. Connection Methods for the OAG-L...
