• DayStar FlatCap White Light Solar Filter — 190–209mm Flat Field Filter for Safe Solar Observation
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Daystar

DayStar Flat Cap Imaging Diffuser — 190–209mm Flat-Field Diffuser for Solar Astrophotography

DayStar Flat Cap Imaging Diffuser — 190–209mm Flat-Field Diffuser for Solar Astrophotography

$99.00
$99.00
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The DayStar Flat Cap is an imaging diffuser for solar astrophotography — not a solar filter, but a calibration tool that helps you take clean flat-field frames. It slips over the front of your telescope and blurs the Sun into an even, featureless glow, so a reference "flat" frame records only the dust spots, vignetting, and uneven illumination in your imaging train. Your software then subtracts those artifacts, leaving a cleaner final image of the Sun.

This size fits telescope tubes with a 190–209mm outer diameter. Ships free to the US.

Safety note: the Flat Cap is not a solar filter and offers no eye protection. Only point your telescope at the Sun when a safe, dedicated solar filter or solar telescope is in use.

Who it's for
Solar imagers who want properly calibrated, artifact-free H-alpha or white-light results on large-aperture setups. New to imaging? See our beginner's guide to astrophotography.

  • Flat-field calibration: records vignetting, dust shadows, and pixel-response variations so they can be removed in processing.
  • Gaussian diffuser: blurs the Sun into an even field, leaving only imaging-train defects in the reference frame.
  • Slide-over fit: friction-fits over the front of the tube — no threads or tools required.
  • Broad transmission: passes roughly 350–800nm for white-light and narrowband solar imaging.
  • Sized to your scope: fits 190–209mm tubes.
Specifications
Type Imaging diffuser (flat-field calibration cap)
Purpose Flat-frame calibration for solar astrophotography
Optical Gaussian diffuser, ~4° FWHM divergence, transmits ~350–800nm (approx.)
Fit Method Slide-over friction fit on telescope front
Telescope Tube OD 190–209mm outer diameter
Model / SKU FC210
What's in the Box Flat Cap imaging diffuser for 190–209mm tubes

Is the Flat Cap a solar filter?
No. It is an imaging diffuser and provides no eye protection. Always use a proper solar filter or solar telescope when pointing at the Sun.

What is a flat frame and why do I need one?
A flat frame captures the dust, vignetting, and uneven illumination in your optics so software can subtract them, giving a cleaner, more even final solar image.

How do I choose the right size?
Measure the outer diameter of your telescope tube and pick the Flat Cap whose range covers it — this one fits 190–209mm.

Do flats need special exposures?
Yes. Because the diffuser strongly dims the Sun, flat exposures are much longer than your normal solar exposures.

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Frequently Asked Questions

With a beginner telescope you can see a surprising amount — the craters and mountains on the Moon, the rings of Saturn, the moons of Jupiter, and star clusters like the Pleiades. As you get more comfortable, you can also spot nebulae and distant galaxies. Not sure which beginner telescope is right for you? Check out our Telescope Buying Guide.
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