Daystar Flat Cap Imaging Diffuser
 Daystar Flat Cap Imaging DiffuserDaystar Flat Cap Imaging Diffuser 

Daystar Flat Cap Imaging Diffuser

£81.00✓ 2 year warranty


1x in stock shipped 1-2 working days

About this product

Model:  daystar_fc90
Part Number:  FC90

Taking a Flat field reference image removes the effects of dust spots, vignetting, and filter uniformity.

The DayStar FlatCap is a Gaussian diffuser that is temporarily installed over the front of your telescope when taking flat field reference images.

By strongly blurring the Sun, the only details you will see in the reference image are from defects in your imaging train that can be removed in software.


  • Construction: Spun Aluminium mounting ring with polymer diffuser

  • Intensity distribution: Gaussian​

  • Divergence angle: 4 degrees FWHM

  • Exposure time adjustment factor: 100x longer

  • Maximum field of view: 1 degree with Sun backlight

  • Wavelength transmission range: 350-800nm

  • Operating temperature: -10 to 100°C (14-212°F)

FlatCap is sold by inside diameter of the mounting cap. Measure the outside diameter of the frontmost component of your telescope or ERF, and then round up to the next larger size. For example, a telescope with a 160mm front should use model FC170, and then optionally install the included felt pads for a secure fit.

IMPORTANT: This DayStar FlatCap Gaussian diffuse filter must be used together with a suitable purpose-made solar filter. 


  • FC90 Flatcap - Fits 80-89mm Tube OD or 63mm ERF
  • FC100 Flatcap - Fits 90-99mm Tube OD
  • FC110 Flatcap - Fits 100-109mm Tube OD or 80mm ERF
  • FC120 Flatcap - Fits 110-119mm Tube OD
  • FC130 Flatcap - Fits 120-129mm Tube OD
  • FC140 Flatcap - Fits 130-139mm Tube OD
  • FC150 Flatcap - Fits 140-149mm Tube OD
  • FC154 Flatcap - Fits 145-154mm Tube OD
  • FC160 Flatcap - Fits 150-159mm Tube OD
  • FC170 Flatcap - Fits 160-169mm Tube OD
  • FC180 Flatcap - Fits 170-179mm Tube OD
  • FC190 Flatcap - Fits 180-189mm Tube OD
  • FC210 Flatcap - Fits 190-209mm Tube OD



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