AO-7 Direct Connect Distances

Using a 6.3 Focal Reducer with a SBIG AO-7/CFW-8A/ST-8E can be rewarding and a challenge all at the same time. The challenge is staying within the operating parameters for Focal reducer to CCD chip distances. The AO-7, by its size and SBIG specs, adds 3.5" or 88.9 mm of back focus/focal reducer distance to the optical path. This can be reduced to 2.5" or 63.5 mm by direct attaching it to the camera or color filter wheel (in SBIGs case), and removing the "Captains Wheel" from the front and using a very short adapter to mount the 6.3 reducer. True Technology makes a SCT thread to T-Thread adapter that adds only 3 mm of additional distance to the path. What you then end up with is a total distance of 109 mm from Focal reducer lense to the CCD chip. The pictures below show the parts connected. Total weight for the 6.3 reducer/AO-7/CFW-8A/ST-8E and JMI 2" adapter is just over 5 lbs. I use a JMI NGF-S for focusing and it is rated at 10 lbs, so the loading is approx. 50%.

Click on any thumbnail picture for the larger version
The True Technology adapter is between the Celestron Focal Reducer and the AO-7. It is sold by ADIRONDACK VIDEO ASTRONOMY
A description can be found here: Sctf-t
This shows the entire image train. JMI NGF-S w/RoBoFocus, Celestron F6.3 reducer, True Technology adapter, AO-7, CFW-8A, ST-8E.
A view from the rear, showing the directly connected devices. Another view showing the components connected and ready for imaging.
A closeup of the AO-7 to CFW-8A coupling. Yet another perspective of the whole image train. In addition to minimizing the optical distance, the direct connections make a very rigid, non flexing light path to the chip.