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IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
Baader Photometric UBVRI-I Individual Filter

Baader Photometric UBVRI-I Individual Filter

by Baader Planetarium
SKU BAA-2961750I
$207.00 - $940.00
$207.00
$207.00 - $940.00
$207.00
Price Match Policy!
  • Conforms to the Johnson-Cousins UBVRI Photometric System
  • Optimized for the Bessel I-Band (Infrared)
  • Homofocal Design for Parfocal Operation with other Baader UBVRI filters
  • Advanced Anti-Reflection and Dielectric Coatings
  • Available in 8 formats, including 1.25" and 2" mounted sizes
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • Baader Photometric UBVRI-I Individual Filter

    The Baader Photometric UBVRI-I Filter is an essential tool for scientific astronomical measurement, designed to precisely isolate the infrared I-band as defined by the Johnson-Cousins UBVRI system. Engineered for data acquisition rather than visual appeal, this filter provides the strict, repeatable bandpass required for variable star observation, exoplanet transit timing, and stellar classification. Each filter is manufactured to be homofocal with its U, B, V, and R counterparts, ensuring your optical system remains parfocal when switching between filters during a photometric sequence.

    The Bessel I-Band Standard for Scientific Photometry

    This filter is not a generic infrared-pass filter; it is a scientific instrument designed to conform to the specific transmission curve of the Bessel I-band. This adherence to an established standard allows your measurements to be directly comparable to data from professional observatories and scientific literature worldwide. The result is verifiable, publishable data for your research projects.

    Homofocal Engineering for Parfocal Operation

    For photometric sequences that require cycling through multiple filters, maintaining focus is critical. Baader engineers their UBVRI filters to be homofocal, meaning each filter has an identical substrate thickness and optical effect. This ensures that once you achieve focus with one filter in the set, all others will snap to the same focal point, eliminating the need to refocus and saving critical time during observation.

    • Planeoptically Polished Substrate: Each filter is polished to a high degree of flatness to prevent any degradation of the incoming wavefront, preserving the sharpness of your telescope's optics.
    • Advanced Anti-Reflection Coatings: Multi-layer coatings eliminate ghosting and internal reflections, maximizing signal-to-noise ratio by ensuring that light from your target reaches the sensor without interference.

    Multi-Format Availability: 8 Options from 1.25" to 100x100mm

    The Baader Photometric I-Filter is available in a comprehensive range of 8 sizes to integrate into any imaging train. Whether you are using a small guide camera for transit timings or a large-format CCD on a research-grade instrument, there is a format to match your equipment. Options include standard 1.25" and 2" round mounted filters for common filter wheels, as well as unmounted round and square filters up to 100x100mm for professional camera systems.

    Photometric vs. Imaging Filters: Measurement over Aesthetics

    It is important to understand the distinction between a photometric filter and a standard LRGB or narrowband imaging filter. While an imaging filter is designed to produce visually pleasing color images, a photometric filter is built for metrology.

    • Strict Bandpass: The Baader Photometric I-Filter has a very sharp cutoff and a flat-topped transmission curve that adheres strictly to the Bessel I-band definition. This prioritizes measurement accuracy over capturing faint, out-of-band signal.
    • No IR/UV Cut: Unlike LRGB filters, this filter does not include additional blocking. It is designed to be used with sensors that have a known spectral response, as is standard practice in photometry.

  • What is the primary use for the Baader Photometric I-Filter?

    The Baader Photometric I-Filter is designed for scientific photometry. Its primary application is measuring the brightness of celestial objects in the infrared portion of the spectrum, as defined by the Johnson-Cousins UBVRI system. This is crucial for studying variable stars, monitoring supernova light curves, and analyzing the characteristics of stars and galaxies.

    Is this Baader I-band filter the same as a standard near-IR imaging filter?

    No, they are fundamentally different. A standard near-IR filter has a broad, less-defined passband designed to capture as much signal as possible for imaging. The Baader Photometric I-Filter has a precisely defined, rectangular transmission profile that conforms to the scientific Bessel I-band standard, prioritizing measurement accuracy and repeatability over raw signal.

    How would I use the Baader I-Filter to measure a variable star like Mira (Omicron Ceti)?

    Mira is a long-period variable star whose brightness changes significantly, especially in the infrared. To measure its magnitude with the Baader I-Filter, you would take a series of exposures of Mira, along with several nearby, non-variable "comparison" stars of known I-band magnitude. Using photometry software, you would measure the instrumental magnitude of all stars and use the known magnitudes of the comparison stars to calibrate your measurement of Mira, producing a standardized I-band magnitude for your observation time.

    Why is the homofocal design of the Baader Photometric I-Filter important?

    The homofocal design means all Baader UBVRI filters have the same optical thickness, making them parfocal. When you are taking photometric measurements, you often need to cycle through U, B, V, R, and I filters quickly. A parfocal set means you only have to focus once. When you switch filters, the image remains sharp, which is critical for automated data acquisition and maintaining consistency across your dataset.

    Do I need the entire UBVRI set to use the Baader I-Filter?

    No, you can use the Baader I-Filter on its own for projects specifically requiring I-band data. However, its true power is realized as part of the complete UBVRI set, which allows you to determine the color indices (like V-I) of stars. These color indices are essential for determining a star's temperature, spectral type, and other physical properties.

    Which Baader filter format is best for my SBIG STX-16803 camera on a PlaneWave CDK?

    For a large-format camera like the SBIG STX-16803, which often uses a 7-position or 8-position filter wheel, you would typically use one of the larger unmounted square formats. The 50x50mm Square Unmounted option is a common standard for this class of instrument, as it is large enough to prevent vignetting on the large KAF-16803 sensor, even with a fast optical system like a PlaneWave CDK.

  • Filter Type Photometric Bessel I-Band
    System Johnson-Cousins UBVRI
    Parfocal Yes, homofocal with other Baader UBVRI filters
    Coatings Dielectric and Anti-Reflection
    Substrate Planeoptically Polished Glass
    Available Options 1.25" Mounted, 2" Mounted, 31mm Unmounted, 36mm Unmounted, 50mm Unmounted, 50x50mm Unmounted, 65x65mm Unmounted, 100x100mm Unmounted
    Net weight (kg) 0.01 (1.25" Round Mounted, 2" Round Mounted, 50mm Round Unmounted)
    0.02 (50x50mm Square Unmounted)
    0.03 (65x65mm Square Unmounted)
    0.08 (100x100mm Square Unmounted)
    Filter size 1.25 inch (1.25" Round Mounted)
    2 inch (2" Round Mounted)
    31 mm (31mm Round Unmounted)
    36 mm (36mm Round Unmounted)
    50.4 mm (50mm Round Unmounted)
    50 x 50 mm (50x50mm Square Unmounted)
    65 x 65 mm (65x65mm Square Unmounted)
    100 x 100 mm (100x100mm Square Unmounted)
    Filter shape round (1.25" Round Mounted, 2" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted)
    square (50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted)
    Single or Set? Single Filter
    Filter mounted Mounted (LPFC 6mm) (1.25" Round Mounted, 2" Round Mounted)
    Unmounted (31mm Round Unmounted, 36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted)
    Filter Usage CMOS, CCD, UBVRI
    Special Features Life-Coat™ Warranty
    Filter Thickness (without cell) 2 mm (1.25" Round Mounted, 2" Round Mounted, 31mm Round Unmounted, 36mm Round Unmounted)
    3 mm (50mm Round Unmounted, 50x50mm Square Unmounted, 65x65mm Square Unmounted, 100x100mm Square Unmounted)
    CWL (Central Wavelength) UBVRI-I
    Transmission Range Transmission according to Bessel
    AR-Coating Reflex-Blocker™ hard coated, planeoptically polished
    Suitable for f/ratio f/15 to f/1.8
  • Baader Planetarium Warranty