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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 SLOAN/SDSS u' Individual Filter
Baader Photometric SLOAN/SDSS u' Individual Filter

Baader Photometric SLOAN/SDSS u' Individual Filter

by Baader Planetarium
SKU BAA-2961700U
$199.00 - $893.00
$200.00
$199.00 - $893.00
$200.00
Price Match Policy!
  • Standardized SLOAN/SDSS u'-band photometric filter
  • Isolates the near-ultraviolet (UV) spectrum for scientific analysis
  • Designed for repeatable, high-precision stellar magnitude measurements
  • Ideal for pro-am collaboration, variable star research, and exoplanet transits
  • Available in multiple mounted and unmounted sizes for various filter wheels
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Downloads
  • Warranty

  • Baader Photometric SLOAN/SDSS u' Individual Filter

    The Baader Photometric SLOAN/SDSS u' Filter is a specialized scientific instrument designed for precise data acquisition in the near-ultraviolet spectrum. This is not a filter for creating color composites; its purpose is to isolate a specific spectral window defined by the Sloan Digital Sky Survey, enabling astronomers to measure the brightness of celestial objects with the high accuracy required for research-grade photometry. It is a critical tool for studying high-energy astronomical phenomena, such as cataclysmic variables, hot young stars, and active galactic nuclei.

    The Role of the u'-Band in Photometry

    The u' (ultraviolet) band is the shortest wavelength filter in the five-filter SLOAN/SDSS system. It provides a unique window into high-energy astrophysical processes that are faint or invisible at longer wavelengths. By measuring flux in the u'-band, you can characterize the temperature of very hot O- and B-type stars or quantify the violent accretion processes occurring in binary star systems.

    This filter's strict adherence to the SDSS standard ensures your data is comparable to that from professional surveys, making it invaluable for pro-am collaborations. Whether you are contributing to the AAVSO database or conducting independent research, the Baader u' filter provides a standardized, repeatable measurement baseline.

    The u' Filter vs. Other SLOAN/SDSS Bands

    While the u' filter is powerful on its own, its true scientific utility is often realized as part of the complete u'g'r'i'z' set. Each filter provides a piece of the puzzle for determining an object's temperature, composition, and distance through color indices.

    • u' vs. g' and r': The u'-band is essential for measuring the "Balmer break" in stellar spectra, a key indicator of temperature and surface gravity. A u'-g' color index is far more sensitive to temperature variations in hot stars than a g'-r' index alone.
    • Trade-offs: The trade-off for this specialized scientific capability is its unsuitability for general-purpose imaging. The u'-band image will appear dim, have low contrast, and will not contribute to a natural-color LRGB composite. This filter is exclusively for data collection with a monochrome sensor.

    Engineered for Repeatable Scientific Measurement

    A filter's "photometric" designation implies a higher standard of manufacturing. While specific transmission values are not provided, these filters are designed with the core requirements of scientific measurement in mind: steep bandpass slopes to cleanly isolate the desired wavelength, and stable, non-ageing coatings to ensure that measurements taken years apart remain consistent.

    Baader's construction aims to minimize halos and internal reflections, preserving the integrity of stellar point-spread functions (PSFs) for accurate magnitude extraction. Available in a wide range of sizes from 1.25" mounted to 100x100mm unmounted, the Baader u' filter can be integrated into nearly any amateur or institutional imaging train.

  • What is the Baader Photometric u' filter primarily used for?

    The Baader u' filter is a scientific tool used with a monochrome camera for photometry—the precise measurement of an object's brightness. It's specifically used to study objects that are bright in the near-ultraviolet, such as hot young stars, accretion disks around white dwarfs (cataclysmic variables), and distant quasars.

    Can I use the Baader u' filter for visual observing or color imaging?

    No, this filter is not suitable for either. Visually, the near-UV bandpass will result in an extremely dim, colorless image. For color imaging (LRGB), the u' band does not correspond to a standard color channel and will not produce a natural-looking result. It is designed exclusively for scientific measurement with a monochrome sensor.

    How would I use the Baader u' filter to study a cataclysmic variable like SS Cygni with my SCT?

    SS Cygni is a dwarf nova that undergoes dramatic outbursts. The source of these outbursts is the accretion disk, which becomes extremely hot and bright in the ultraviolet. Using the Baader u' filter on your SCT with a monochrome camera, you can take a series of exposures and measure the changing brightness of SS Cygni relative to nearby, stable stars. This allows you to create a light curve of the outburst in the u'-band, providing critical data on the physics of the accretion process.

    Do I need the entire Baader SLOAN/SDSS filter set for my research?

    It depends on your goal. For monitoring the brightness of an object in a single high-energy band, the u' filter alone is sufficient. However, to determine an object's temperature or create a Spectral Energy Distribution (SED), you need to measure its brightness through multiple filters (e.g., u', g', and r') to calculate color indices.

    Will the Baader u' filter work with my observatory's automated filter wheel?

    Yes. The Baader u' filter is offered in all standard astronomical sizes, including 1.25" and 2" mounted for smaller wheels, and unmounted round (31mm, 36mm, 50mm) and square (50x50mm, 65x65mm, 100x100mm) formats for larger, research-grade filter carousels. Be sure to select the option that matches your filter wheel's specifications.

    What makes this Baader u' filter "photometric"?

    A "photometric" filter is manufactured to meet a strict transmission standard, in this case, the Sloan Digital Sky Survey u' band. This ensures that data you collect is consistent and can be compared directly with data from other observers and professional surveys using the same system. The design emphasizes sharp bandpass cutoffs, high transmission, and coating stability over time.

  • Filter Type Photometric SLOAN/SDSS u' Bandpass Filter
    Available Sizes 1.25" Mounted, 2" Mounted, 31mm Unmounted, 36mm Unmounted, 50mm Unmounted, 50x50mm Square, 65x65mm Square, 100x100mm Square
    Net weight (kg) 0.01 (1.25" Round Mounted, 2" Round Mounted, 50mm Round Unmounted)
    0.02 (50x50mm Square Filter)
    0.03 (65x65mm Square Filter)
    0.08 (100x100mm Square Filter)
    Filter size 1.25 inch (1.25" Round Mounted)
    2 inch (2" Round Mounted)
    36 mm (36mm Round Unmounted)
    50.4 mm (50mm Round Unmounted)
    50 x 50 mm (50x50mm Square Filter)
    65 x 65 mm (65x65mm Square Filter)
    100 x 100 mm (100x100mm Square Filter)
    Filter shape round (1.25" Round Mounted, 2" Round Mounted, 36mm Round Unmounted, 50mm Round Unmounted)
    square (50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)
    Single or Set? Single Filter
    Filter mounted Mounted (LPFC 6mm) (1.25" Round Mounted, 2" Round Mounted)
    Unmounted (36mm Round Unmounted, 50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)
    Filter Usage SLOAN, CMOS, CCD
    Special Features Life-Coat™ Warranty
    Filter Thickness (without cell) 2 mm (1.25" Round Mounted, 2" Round Mounted, 36mm Round Unmounted)
    3 mm (50mm Round Unmounted, 50x50mm Square Filter, 65x65mm Square Filter, 100x100mm Square Filter)
    CWL (Central Wavelength) SLOAN-u'
    Transmission Range Transmission according to SLOAN-Specification
    AR-Coating Reflex-Blocker™ hard coated, planeoptically polished
    Suitable for f/ratio f/15 to f/1.8

    • Baader Photometric SLOAN/SDSS u' Individual Filter (selected size)

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  • Baader Planetarium Warranty