Lunático Astronomía

Baader Planetarium Photometrics U-Filter


Baader Planetarium, amplia gama de filtros para astrofotografía y fotometría con muy buena relación calidad-precio.


Baader UBVRI Photometric U-Filter

  • U filter
  • Photometric Johnson/Bessel filter system
  • partial dielectric design with BBAR minimized reflections
  • Planeoptically polished, 4mm glass thickness
  • non-ageing sealed coating edges

Baader UBVRI Filters – Specifications

Baader 4 mm thick UBVRI filters feature a proprietary design that strictly adheres to the classic Johnson/Bessel transmission specification. Unlike the classic construction that regularly has a thickness of 5mm or more, the Baader-filters are made of dielectric layers as well as absorption glasses. This allows for a smaller filter thickness of 4 mm. The original stack of pure colored glass had a thickness of 5 or 6 mm and would be too thick and too heavy for modern filter wheels.

In the old days, UBVIR-filters were used for photodetectors and no one would care if the huge stack of cemented absorption glasses would cause havoc in terms of inherent internal reflections. Our method of combining dielectric coatings with a combination of a short pass and long pass filters does provide for perfect off-band blocking into the far ends of the spectrum. This steep off-band-blocking would not be possible with pure dielectric layers over such a large transmission range.

Transmission curve:

Technical Data:

FILTER SIZE 1 25 inch 50 x 50 mm
MANUFACTURER Baader Planetarium  Baader Planetarium
SKU (#) 2459440U 2459444U
EAN CODE 4047825101761
WEIGHT (KG) 0.029 0.029
TRANSMISSION RANGE Transmission range after Bessel multiple bands (see spectral image)
AR-COATING dielectrically coated, planeoptically polished dielectrically coated, planeoptically polished
FILTER USAGE Specialty, UBVRI Specialty, UBVRI
FILTER MOUNTED Mounted (LPFC 6mm) Unmounted
TYPE OF FILTER Bandpass Bandpass
SINGLE OR SET? Single Filter Single Filter
FILTER SHAPE round square

If you have any doubt, contact us at

Filter thread

1,25", 50x50mm.

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