How does the Baader BFM-OAG attach to the FlipMirror II?
The Baader BFM-OAG is designed to connect directly to the 19 mm nosepiece port located on the bottom of the Baader FlipMirror II diagonal. This provides a secure, dedicated connection point that keeps the guider perfectly aligned with the optical train.
What is the purpose of the 4mm spacer ring on the Baader BFM-OAG?
The 4mm spacer ring adjusts how far the pick-up prism intrudes into the light path. Removing it sets the prism at the optimal 17.5mm offset for maximum guide field illumination. However, if this causes any obstruction in your specific optical setup, you can re-install the ring to pull the prism back slightly, at the cost of a marginally smaller illuminated area for guiding.
Can I use the Baader BFM-OAG without a FlipMirror II?
No, this unit is specifically designed to mate with the FlipMirror II's bottom port. To use this OAG with a standard telescope setup, you would need the complete Baader Off Axis Guider for RCC (RCC-OAG) #2956950, which includes this prism assembly along with the necessary T-2 adapters.
My guide camera is not parfocal with my main camera using the Baader BFM-OAG. How do I fix this?
You need to adjust the distance of the guide camera from the OAG body. The easiest way to do this is with spacing rings or dedicated extenders. Baader recommends using one or two DT-4 nosepiece extensions (#1905130), which thread into the 1.25" filter threads of your guide camera to push it further out until it reaches the same focal plane as your main imager.
I'm imaging Jupiter with a planetary camera on my FlipMirror II's top port. Can I still guide with the Baader BFM-OAG?
Yes, absolutely. The BFM-OAG prism is located in the body of the FlipMirror II, below the mirror itself. This means it picks off guide stars from the incoming light path before the light hits the flip mirror. As a result, the OAG functions perfectly whether the mirror is down (sending light to the top port) or up (sending light to the rear port).
When using the Baader BFM-OAG with my SCT and a DSLR, where should the prism be positioned?
For the best results with a rectangular sensor like that in a DSLR, the FlipMirror II body should be oriented so the OAG prism sits under the long side of the camera sensor. This placement allows the prism to find guide stars in the largest available off-axis field of view without risk of intruding into the corners of your main image frame.
