What problem does the Starlight Instruments 3.5" Riser solve?
This 3.35" riser solves the problem of having insufficient outward focuser travel. This happens when the telescope's focal plane sits farther behind the focuser than the draw tube can reach. If this distance is greater than your focuser's draw tube can extend, you won't be able to achieve focus. The riser adds a fixed 3.35" of length, pushing your eyepiece or camera back to a point where the focuser can reach the focal plane.
How do I install the 3.35" Riser on my FTF35xx focuser?
Installation is straightforward. First, you unthread and remove the end cap (e.g., the 2" compression ring adapter) from your 3.5" Feather Touch focuser's draw tube. Then, you thread the riser directly onto the now-exposed draw tube threads. Finally, you thread your original end cap onto the end of the riser.
Will this 3.5" riser introduce any flex into my imaging train?
No. The Starlight Instruments riser threads directly onto the FTF35xx draw tube, below the end cap. This ensures a rigid, secure connection that becomes an integral part of the focuser assembly, preventing tilt and flex even with heavy loads.
Can I use this 3.5" riser with a 2" or 2.5" Feather Touch focuser?
No, this riser is specifically designed for the 3.5" diameter FTF35xx series of Feather Touch focusers. It will not fit focusers with smaller diameter draw tubes.
I'm trying to use a binoviewer with my large refractor and FTF35xx focuser, but I can't reach focus. Is this 3.35" riser the right solution?
No. A binoviewer's long optical path needs more inward travel, and the riser moves the binoviewer farther out, which makes the problem worse. The riser only helps when focus lies beyond the draw tube's outward travel.
My custom imaging train on my Ritchey-Chrétien telescope places the sensor too far away from the FTF35xx focuser to reach focus. Will this 3.35" riser help?
No. If the sensor already sits too far from the focuser, the riser adds another 3.35" (85 mm) and moves it farther out, because it reduces the remaining backfocus. Shorten the imaging train instead. The riser helps only when focus lies beyond the draw tube's outward travel.
