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Starlight Instruments 3.5" Diameter Riser
The Starlight Instruments 3.5" Diameter Riser provides a critical 4.0" of height extension, enabling you to achieve focus in optical configurations where the focal plane sits significantly outside the stock focuser's travel range.
4.0" Draw Tube Extension for 3.5" Feather Touch Focusers
Designed for Newtonian telescopes and custom builds, this riser addresses the common problem of insufficient outward focus travel. By threading this 4.0" riser onto the draw tube of your 3.5" Feather Touch focuser, below the end cap, you extend the draw tube by 4.0" to meet a distant focal plane without compromising stability.
Starlight Instruments Build and System Integration
As a genuine Starlight Instruments component, this riser is not a generic spacer. It is machined in-house from high-grade aluminum to the same exacting tolerances as the Feather Touch focusers themselves. This ensures a perfect, rigid fit that prevents tilt or flex, preserving the mechanical integrity of your high-precision focusing system even with heavy cameras or accessory loads.
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How do I know if I need the Starlight Instruments 4.0" Riser?
You need a riser if your focuser runs out of outward travel before your eyepieces or camera can reach a sharp focus. This is common in Newtonian telescopes where the mirror's focal plane is positioned far from the tube wall. Measure the distance from your focuser's fully racked-out position to where focus is achieved to determine the required riser height.
Is the 3.5" Diameter Riser compatible with other focuser brands?
No. This riser is specifically designed to thread onto the draw tube of Starlight Instruments 3.5" Feather Touch focusers. It will not fit focusers or bases from other manufacturers.
Will adding the 4.0" riser introduce flex into my imaging setup?
The Starlight Instruments 4.0" Riser is machined from solid material to be extremely rigid. When properly installed, it is designed to provide a solid, stable extension that does not introduce flex into the focusing system, maintaining the precision necessary for critical imaging.
Can I stack multiple Starlight Instruments risers to get more height?
While mechanically possible, stacking risers is not recommended. Each additional component connection is a potential source of flex or tilt. It is always best to use a single riser of the correct height for maximum stability.
Will this riser work with my 2" or 2.5" Feather Touch focuser?
No. This model has a 3.5" diameter intended for Starlight's largest focusers, such as the FTF35xx series. You must use a riser that matches the draw tube diameter of your specific focuser.
What hardware is needed to install the 3.5" Diameter Riser?
No extra hardware is needed: remove the end cap, thread the riser directly onto the draw tube on the viewing side of the focuser, then thread the end cap onto the riser.
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| Diameter |
3.5" |
| Riser Height |
Adds 4.0" to draw tube length |
| Compatibility |
Starlight Instruments 3.5" Feather Touch focuser draw tube |
| Kind |
Draw tube extension |
| Optical length (added light path) |
4.0" (101.6 mm) |
| Telescope-side connection |
Threads onto 3.5" Feather Touch draw tube |
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3.5" Diameter Riser (4.0" Height)
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Starlight Instruments 2-Year Warranty
