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DayStar 90mm Off-Axis ERF with 325mm Inside Diameter Cap

by DayStar
SKU E-325F90
Original price $695.00 - Original price $695.00
Original price
$695.00 - $695.00
Current price $695.00
In stock

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DayStar 90mm Off-Axis Energy Rejection Filter with 325mm Inside Diameter Cap - for 11-inch SCT - E-325F90

Discover the DayStar 90mm Off-Axis Energy Rejection Filter, complete with a 325mm Inside Diameter Cap and tailored for 11-inch SCT telescopes, offers a solution to minimize the heat generated by your filter system.

It achieves this by either absorbing or reflecting harmful UV and/or IR light while permitting the transmission of light within the desired visual spectrum.

These filters are typically fashioned from red or yellow glass, or they may employ dielectric coatings to block IR and UV, ensuring that only desired visible light is allowed through.

Additionally, the ERF can double as an aperture mask, helping to maintain an optimal angle for incoming light.

DayStar filter systems work most effectively when used with telescopes operating at f/30 or slower.

Achieving an f/30 setup is a straightforward task when you have the right ERF and/or Barlow lens at your disposal.

This ensures that your observations are carried out with the utmost precision and image quality.

 Important Instructions:

To facilitate a seamless integration, after your order is placed, please reach out to us via email with the following details:

  • Please specify the telescope intended for use with this ERF and meticulously measure the outer diameter of the telescope's dew shield at the front using a ruler. This precise measurement is paramount, as ERFs are custom made on an individual basis to ensure a perfect fit.
  • Failure to provide this measurement may result in a temporary hold on your order until the necessary information is retrieved. Your satisfaction and optimal performance is our priority.

Features & Highlights:

  • 90mm ERF Glass: Crafted with precision, the 90mm ERF aperture is expertly tailored for optimal solar observation. Striking a perfect balance between light-gathering capacity and resolution, it delivers crisp, detailed views of solar phenomena.
  • 325mm Inside Diameter Cap: Included in the package is a 325mm inside diameter cap, ensuring a secure and snug fit with compatible telescopes. This cap plays a pivotal role in minimizing stray light, enabling precise and unobstructed solar observations.
  • SCT Compatibility: Engineered specifically for 11-inch SCT (Schmidt-Cassegrain) telescopes, the ERF seamlessly integrates with your existing optical setup. This ensures a seamless, hassle-free, and effective solar observation experience.
  • Advanced Energy Rejection: The ERF is meticulously designed to significantly diminish the heat load on your filter assembly. This is accomplished through efficient absorption or reflection of UV and/or Infrared light, allowing the transmission of light within the desired visual spectrum.
  • Multi-Coated Optics: All optical surfaces are expertly multi-coated to enhance light transmission and minimize internal reflections. This results in vibrant, high-contrast solar images with exceptional clarity and detail.
  • Off-Axis Design: The off-axis design provides an unobstructed view of the solar disk, maximizing the amount of light collected by the telescope. This design feature ensures precise observation of the sun's features.
  • Dual Functionality as an Aperture Mask: The ERF serves a dual purpose as an aperture mask, guaranteeing a direct angle of incidence for incoming light. This unique feature enhances filtering efficiency, ensuring that only the desired wavelengths are transmitted.
  • Robust Construction: Constructed from high-quality materials, the ERF guarantees durability and longevity. It is designed to withstand the demands of outdoor use and maintain peak performance over time.
  • Recommendations for Optimal Performance: For the best results, DayStar recommends operating filter assemblies at f/30 or slower. This configuration is effortlessly achieved with the appropriate ERF and/or Barlow. In cases of higher resolution or larger aperture configurations, the addition of a Barlow is recommended for an enhanced viewing experience.


            What's Included:

            ✓ DayStar 90mm Off-Axis ERF for 11-inch SCT

             ✓ 5 Year Warranty



            SKU E-325F90
            Block Ultraviolet Yes
            Block Infrared Yes

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