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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.
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.

Astronomical Filter Transmission & Bandpass Measurement Service

by David Astro
SKU DAV-SPECTRO
$35.17 - $35.17
$35.17
$35.17 - $35.17
$35.17
Price Match Policy!
  • 350nm to 1050nm Spectral Range
  • 1.5nm Spectral Resolution
  • Calibrated Peak Transmission Accuracy
  • Full FWHM and CWL Verification
  • Rotation-based Uniformity Testing
Qualifies for FREE Shipping in CONUS on orders over $350.
  • Description
  • FAQ
  • Specifications

  • Astronomical Filter Transmission & Bandpass Measurement Service

    The Astronomical Filter Transmission & Bandpass Measurement Service provides empirical verification of optical filter performance using a calibrated spectrometer with 1.5nm spectral resolution. By measuring the actual transmission curve rather than relying on nominal manufacturer data, this service identifies the specific Central Wavelength (CWL) and Full Width at Half Maximum (FWHM) of your individual optic.

    Spectral Precision and Bandpass Characterization

    Thin-film coatings can vary across production batches, leading to shifts in transmission peaks that affect signal-to-noise ratios in narrowband imaging. Measurements are optimized for filters with bandpasses of 5nm and wider, providing high-fidelity data for broadband and wide-narrowband optics.

    • Peak Transmission (%): Measure the exact percentage of light passing through the desired bandpass to quantify potential signal loss.
    • CWL Accuracy: Identify if the filter's peak is centered on the target emission line or shifted due to manufacturing tolerances or aging.
    • FWHM Verification: Confirm the actual bandwidth of filters to determine their effectiveness in suppressing light pollution or moonlight.

    Narrowband Analysis and Instrumental Constraints

    While our service is optimized for 5nm+ bandpasses, narrower filters can be analyzed with appropriate data interpretation. At 1.5nm resolution, the instrumental profile may broaden the measured FWHM of ultra-narrowband filters (e.g., 3nm), requiring deconvolution for true width estimation. We will do the deconvolution to get the true width estimation.

    • Instrumental Broadening: Understand how the 1.5nm spectrometer resolution interacts with the physical filter width.
    • Relative Peak Analysis: Ensure your Hydrogen-alpha (Ha) or Oxygen III (OIII) peak alignment is consistent across your filter set.

    Operational Comparison

    Understanding the difference between lab-grade testing and manufacturer marketing specs is vital for high-end astrophotography.

    • vs. Nominal Manufacturer Specs: While factory charts represent idealized batches, individual measurement reveals the unique "fingerprint" and actual deviations of your specific unit.

  • Can the Astronomical Filter Transmission Service measure 3nm narrowband filters?

    Yes, though at 1.5nm resolution, the measured FWHM will appear slightly broader than the true physical width due to instrumental convolution. The measurement remains highly accurate for determining Central Wavelength (CWL) alignment.

    Why is the Astronomical Filter Transmission Service optimized for 5nm filters and wider?

    At 5nm and wider, the 1.5nm spectrometer resolution has a negligible effect on the transmission curve shape. This ensures the peak transmission percentage and bandwidth data are captured with maximum fidelity.

    Does the service include testing for IR-cut leakage?

    The standard Full Spectral Analysis scans up to 1050nm, effectively identifying any significant Infrared (IR) leaks that could cause bloated stars in sensors with high NIR sensitivity.

  • Spectral Range 350nm – 1050nm
    Spectral Resolution ~1.5nm
    Optimization Bandpasses ≥ 5nm
    Measured Metrics CWL, FWHM, Peak %, Uniformity
    Compatibility 1.25", 2", 31mm, 36mm, 50mm, 50mm²
    Turnaround Time 1–3 Business Days