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Starlight Instruments 3.5" Base Flat w/ Leveling Screws
The Starlight Instruments 3.5" Flat Base provides a solid, adjustable foundation for the 3.5" Feather Touch focuser, featuring a 5.25" center-to-center mounting hole pattern for securing to custom telescope back plates or other flat mounting surfaces.
Precision Mounting for 3.5" Focusers with a 5.25" Hole Pattern
This heavy-duty base is the starting point for integrating a premium 3.5" Feather Touch focuser into a custom instrument with a flat mounting surface. The integrated leveling screws are essential for achieving perfect alignment of the optical axis, allowing you to collimate the focuser and eliminate image train tilt—a critical step for serious astrophotography.
Critical Compatibility: The M138x1 A35-503-TMB Adapter
This base does not attach directly to the focuser. It is engineered to connect with the Starlight Instruments A35-503-TMB tube adapter ring, which features M138x1 threads. The focuser then mounts to the adapter ring, creating a secure, rotatable, and precisely aligned system. Both the 3.5" Feather Touch Focuser and the A35-503-TMB adapter ring must be purchased separately.
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What is the purpose of the leveling screws on the Starlight Instruments 3.5" Flat Base?
The leveling screws allow you to make fine adjustments to the tilt of the entire focuser assembly. This is crucial for ensuring the focuser's drawtube is perfectly perpendicular to the focal plane, which prevents elongated stars at the corners of your images and is essential for precise collimation of the imaging train.
Can I mount a 3.5" Feather Touch focuser directly to this flat base?
No. This base requires the A35-503-TMB Tube Adapter Ring (sold separately) to act as an interface. The base threads into the adapter ring, and the 3.5" Feather Touch Focuser then attaches to the adapter ring.
What are the mounting hole dimensions for this 3.5" flat base?
The base has a mounting hole pattern of 5.25 inches from center to center. You will need to drill your mounting surface to match this pattern.
Is this Starlight Instruments base suitable for a curved telescope tube like a Newtonian?
No, this model is a flat base designed specifically for flat surfaces, such as the rear cell of a Ritchey-Chrétien or a custom-built instrument. For standard Newtonian tubes, you would need a curved base that matches your telescope's tube diameter.
I'm building a custom telescope with a flat mounting surface; does this base include hardware?
Yes, the base comes complete with the necessary mounting hardware to attach it to your telescope's flat surface. The specific bolts or screws to attach the focuser and adapter ring are part of those respective components.
How does the Starlight Instruments 3.5" Base connect to the A35-503-TMB adapter ring?
The base is threaded and screws directly into the A35-503-TMB tube adapter ring. This creates a solid, unified component that you can then attach your 3.5" Feather Touch focuser to.
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Starlight Instruments 2-Year Warranty
