• DayStar 115mm Off-Axis ERF with 410mm Cap — Solar Filter for H-Alpha Observation on Large SCT Telescopes
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Daystar

DayStar 125mm Off-Axis ERF with 460mm Cap — Solar Filter for H-Alpha Observation on Large SCT Telescopes

DayStar 125mm Off-Axis ERF with 460mm Cap — Solar Filter for H-Alpha Observation on Large SCT Telescopes

$1,195.00
$1,195.00
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The DayStar 125mm Off-Axis ERF (Energy Rejection Filter) is a front-mounted solar filter designed for large Schmidt-Cassegrain and other catadioptric telescopes. Instead of a centered opening, the red-glass ERF sits off to one side of a full front cap, so it clears the telescope's central obstruction (the secondary mirror) and gives an unobstructed 125mm solar aperture. It blocks most of the Sun's ultraviolet and infrared energy while passing the visible red light around the hydrogen-alpha line (~656nm), protecting your Quark or Quantum sub-filter from heat.

The full cap has a 460mm inner diameter that slides over the front of your SCT's corrector cell. Ships free to the US.

Safety note: a red-glass ERF is a pre-filter, not a complete solar filter. It must be used together with a proper H-alpha filter (Quark/Quantum) or solar telescope — never view the Sun through the ERF alone.

Who it's for
Large SCT and catadioptric owners running a DayStar Quark or Quantum who need a large off-axis front ERF that clears the central obstruction. New to filters? See our guide to telescope filters.

  • Off-axis design: the aperture sits to one side, clearing an SCT's central obstruction.
  • Full-aperture red glass: blocks most UV and IR, passes visible light including H-alpha.
  • 125mm clear aperture: a large unobstructed off-axis opening for high-resolution solar work.
  • 460mm cap (ID): slides over the front of a large Schmidt-Cassegrain corrector cell.
  • Reduces heat load: protects your Quark/Quantum sub-filter and steadies the image.
Specifications
Type Off-axis front energy-rejection filter (red glass)
Clear Aperture 125mm (off-axis)
Cap ID 460mm (slides over SCT corrector cell)
Function Blocks UV/IR, passes visible (incl. H-alpha ~656nm)
Designed For Large SCT / catadioptric telescopes
Model / SKU E-460F125

Why off-axis?
An SCT has a central obstruction from its secondary mirror. An off-axis ERF places the clear aperture to the side so light reaches the filter unobstructed.

Do I need one?
A front ERF is recommended when using a Quark or Quantum on larger apertures or for long solar sessions.

How do I choose the cap size?
Match the cap inner diameter to your telescope's front corrector cell — this one has a 460mm cap.

Is it a complete solar filter?
No. It is a pre-filter used with a Quark or Quantum H-alpha filter — never view the Sun through the ERF alone.

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Frequently Asked Questions

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