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IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
Starlight Instruments 3.5" End Cap w/ 3.0" Compression Ring Opening

Starlight Instruments 3.5" End Cap w/ 3.0" Compression Ring Opening

by Starlight Instruments
SKU SI-EC35-505-3CR
$200.00 - $200.00
$200.00
$200.00 - $200.00
$200.00
Price Match Policy!
  • Adapts 3.5" Feather Touch focusers to accept 3.0" accessories
  • Provides a secure, non-marring grip with a brass compression ring
  • Ideal for heavy imaging trains with large format cameras and correctors
  • Features three adjustment screws for precise optical train collimation
  • Machined from high-grade aluminum for rigidity and durability
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  • Description
  • FAQ
  • In the Box
  • Downloads
  • Warranty

  • Starlight Instruments 3.5" End Cap w/ 3.0" Compression Ring Opening

    The Starlight Instruments 3.5" End Cap provides a robust, non-marring connection for your 3.0" accessories. This adapter is specifically designed for the Starlight Instruments 3.5" series of Feather Touch focusers, enabling you to securely attach large format cameras, field flatteners, or other 3.0" barrel components to your imaging train.

    Secure Your Imaging Train: Adapting 3.5" Focusers to 3.0" Accessories

    This end cap is the essential interface for connecting modern 3.0" imaging accessories to a Starlight Instruments 3.5" Feather Touch focuser. It replaces the focuser's standard end cap, providing a large, secure 3.0" opening that is critical for avoiding vignetting with full-frame or larger sensors while maintaining perfect alignment.

    • Direct Fit: Threads directly onto the drawtube of a 3.5" Feather Touch focuser, ensuring a solid, flex-free connection.
    • Brass Compression Ring: The internal brass ring clamps down evenly on your 3.0" accessory barrel, preventing scratches and providing a more secure grip than simple set screws.
    • Heavy-Duty Support: Engineered to hold heavy imaging trains consisting of cameras, filter wheels, and adaptive optics without flexure or sag.

    Collimation Control: 3-Point Tilt Adjustment Screws

    Achieving a perfectly flat field requires precise alignment of the entire optical train. This end cap features three integrated set screws, allowing you to make fine tilt adjustments directly at the focuser. This capability is crucial for eliminating field tilt caused by slight sensor misalignment or mechanical tolerances in your imaging setup, ensuring sharp stars from corner to corner.

  • What focusers is the Starlight Instruments 3.5" End Cap compatible with?

    This end cap is specifically designed for the Starlight Instruments 3.5" Feather Touch focuser series, such as the FTF35xxB-A models. It threads directly onto the focuser's drawtube, replacing the original end cap.

    How does the compression ring on this 3.0" end cap help when imaging with a heavy camera like a ZWO ASI6200MM Pro?

    The brass compression ring provides a full-circumference grip on the 3.0" barrel of your camera or accessory. This distributes the clamping force evenly, preventing the accessory from tilting and holding it more securely than single-point set screws, which is critical for maintaining collimation with a heavy imaging train.

    What is the purpose of the tilt adjustment screws on the Starlight Instruments 3.5" End Cap?

    The tilt adjustment screws allow you to make minute changes to the angle of your attached camera or accessory. This is used to correct for field tilt, ensuring your camera sensor is perfectly perpendicular to the light path for sharp, round stars across the entire image frame.

    Why would I use this 3.0" compression ring end cap instead of a threaded adapter?

    A compression ring offers more flexibility. It allows for easy rotation of your camera to frame your target and is quicker to attach and detach accessories. While a threaded connection is also secure, this 3.0" compression end cap provides convenience without sacrificing a solid mechanical connection.

    I'm using a large refractor with a 3.5" Feather Touch focuser and a 3.0" field flattener. Is this the right part?

    Yes, this is the exact component you need. The Starlight Instruments 3.5" End Cap with a 3.0" compression ring opening will thread onto your focuser's drawtube and allow you to securely mount your 3.0" field flattener, maintaining the rigidity of your imaging system.

    Will this Starlight Instruments end cap mar the barrel of my expensive 3.0" accessories?

    No. It uses a soft brass compression ring. When you tighten the thumbscrews, the brass ring is what makes contact with your accessory's barrel. This prevents the steel screws from digging in and causing scratches or gouges.

    • 3.5" End Cap w/ 3.0" Compression Ring Opening

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  • Starlight Instruments 2-Year Warranty