Dave's 16 Inch Binocular Telescope Page

 

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The main reason that I chose curved spider vanes was for viewing believability. I believe that visual astronomy needs to project a believable view to truly engage your mind. If you look through most standard telescopes you will almost always see moderate to large size diffraction spikes caused by the straight spider vanes. Now imagine what would happen if you were to try and view this image through both eyes simultaneously. The unfortunate thing is that the diffraction spikes would be rotationally offset to one another. You would see eight diffraction spikes and your brain would not be able to make sense of the image it was seeing and ruin the reality effect.  This would mostly be a problem of course on bright stellar sources.

Using curved spider vanes the diffraction energy is still present however it is an a circular pattern. This sometimes makes the brighter stars to always appear out of focus or slightly bloated. However the real appearance when seen with both eyes is perfectly acceptable, making such things as open clusters, often with red giant stars among them appear to hang silently just out of reach as if through a porthole window. Only on extremely bright stars is this bloating effect noticeable.

The vanes are made from plate steel, these were then cut and rolled by a local engineering firm. The hubs are made up of two circular pieces of Bakelite held apart with three pieces of aluminum strap that we drilled and tapped to allow the assembly to be screwed together. Having three separate attachment points for the curved vanes also allowed me to feed power to some secondary heater units via the vanes.

The secondary holder is a standard Novak mirror holder, although at 3.5 in. it is slightly larger than what would normally be considered the correct size for a 16 in. primary mirror. The main reason for this is that due to the teriaries mirrors the secondary mirrors end up approximately 3 in. further away from the focus point. This means that the light cone at the point where it is intersected by the secondaries is slightly larger.