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Antlia 4.5nm Narrowband H-alpha Edge Filter

Antlia 4.5nm Narrowband H-alpha Edge Filter

by Antlia
SKU ANT-HA-4.5NM-1.25
CA$263.00 - CA$497.00
CA$263.00
CA$263.00 - CA$497.00
CA$263.00
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  • 4.5nm Narrowband H-alpha Filter
  • Usable down to f/3 with minimal loss of signal
  • Peak transmission greater than 90% at 656.3nm
  • Out-of-band blocking greater than OD5 (300-1000nm)
  • Single substrate with Lambda/4 or better transmitted wavefront
Size
3 in stock
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • Antlia 4.5nm Narrowband H-alpha Edge Filter

    The Antlia 4.5nm Narrowband H-alpha Edge Filter isolates the critical 656.3nm H-alpha emission line with a tight 4.5nm bandpass and greater than 90% peak transmission. T>90% is guaranteed within 1nm range of the center bandwidth, and blue-shift data shows the filter can be used with nearly all systems as fast as f/3 with minimal loss in emission signal. With out-of-band blocking of over OD5 from 300-1000nm, carried over from the 3nm Pro series, it delivers a superior signal-to-noise ratio and better contrast, in light-polluted areas and at dark sites.

    4.5nm Bandpass: High Contrast on H-Alpha Targets

    With a full width at half maximum (FWHM) of just 4.5nm, this filter lowers the background signal from light pollution, moonlight and natural skyglow, which raises contrast on H-alpha emission nebulae, planetary nebulae, Wolf-Rayet nebulae and supernova remnants. It can be used in light-polluted areas and dark sites, and it extends imaging time when the moon is up. Centered on 656.3nm, it is designed to deliver high transmittance at the H-alpha line.

    EDGE Series: T>90% Within 1nm, Usable Down to f/3

    Conventional broader narrowband filters suffer a heavy loss in transmission from the center wavelength (CWL) shift that occurs with fast focal ratio telescopes. With T>90% guaranteed within 1nm range of the center bandwidth, the filter keeps high transmittance with both long focal ratios and fast optical systems. Blue-shift data shows the 4.5nm EDGE filters can be used with nearly all systems as fast as f/3 with minimal loss in emission signal.

    OD5 Blocking and Lambda/4 Optics to Minimize Halos

    The Antlia 4.5nm EDGE filter provides stringent out-of-band blocking at OD5 (a factor of 100,000) across the 300-1000nm range, for a superior signal-to-noise ratio. It is built on a single, non-glued optical substrate, which eliminates internal reflections, with a transmitted wavefront of Lambda/4 or better and parallelism under 30 arcseconds, and its steep spectral profile minimizes halos around bright stars. All unmounted versions also feature blackened edges to further minimize stray light and internal reflections.

    Antlia 4.5nm EDGE vs. 3nm Pro: Bandwidth and Contrast

    Antlia offers H-alpha filters in several bandwidths, and both the 4.5nm EDGE and the 3nm Pro can be used down to f/3 with minimal loss of signal. The EDGE series carries over the OD5 blocking and transmittance characteristics of the 3nm Pro series.

    • Antlia 3nm Pro: The narrower bandpass lowers the background signal further for higher contrast, with a peak transmission of >88%.
    • Antlia 4.5nm EDGE: A slightly wider bandpass with a peak transmission of >90%, passing more signal per exposure at slightly lower contrast.

  • What makes the Antlia 4.5nm EDGE filter special for fast telescopes?

    The guaranteed T>90% within 1nm range of the center bandwidth keeps transmittance high when the center wavelength shifts in fast optics. Blue-shift data shows it can be used with nearly all systems as fast as f/3 with minimal loss of emission signal, while conventional broader narrowband filters suffer a heavy loss in transmission.

    How will the Antlia 4.5nm H-alpha filter perform on the North American Nebula (NGC 7000) with an f/4 astrograph?

    An f/4 system is within the range for this filter, which can be used down to f/3 with minimal loss of signal. NGC 7000 is a bright H-alpha emission nebula, and the 4.5nm bandpass at 656.3nm improves the contrast of its structures against the background.

    Should I choose the Antlia 4.5nm EDGE or a 3nm Pro filter for my f/5 refractor?

    Both work at f/5, since both series are rated for use down to f/3 with minimal loss of signal. The 3nm Pro gives higher contrast by passing less background light, which helps from light-polluted locations. The 4.5nm EDGE passes more signal per exposure, with a peak transmission of >90% against >88% for the 3nm Pro.

    Is the Antlia 4.5nm H-alpha filter a good choice for imaging the Horsehead Nebula (Barnard 33) from a Bortle 7 zone?

    Yes. The Horsehead is seen in silhouette against the H-alpha glow of IC 434, which this filter records at 656.3nm. The filter can be used in light-polluted areas, and the 4.5nm bandpass rejects much of the city skyglow, improving the contrast of IC 434 against the background.

    Can I use the Antlia 4.5nm EDGE filter for visual observation?

    No. Antlia does not recommend this filter for night visual observation. It is designed for imaging deep-sky objects that contain H-alpha emissions.

    Can I use the Antlia 4.5nm H-alpha filter for imaging the Sun?

    No. This is not a solar filter, and Antlia does not recommend it for solar imaging. DO NOT LOOK AT THE SUN WITH THIS FILTER. Serious eye damage will result if you fail to observe this warning.

  • Filter Type H-alpha narrowband (4.5nm EDGE series)
    Central Wavelength (CWL) 656.3nm
    Bandpass (FWHM) 4.5nm
    Peak Transmission >90%
    Transmission Guarantee T>90% within 1nm range of the center bandwidth
    Out-of-Band Blocking >OD5 @ 300-1000nm
    Recommended F-Ratio Usable down to f/3
    Substrate Optical, single / non-glued substrate
    Transmitted Wavefront Lambda/4 or better
    Parallelism < 30 arcsec
    Surface Quality 60/40 (scratch/dig) per MIL-O-13830
    Filter Thickness 2mm +/-0.05mm (1.25", 31mm, 36mm, 2")
    3mm +/-0.05mm (50mm)
    Filter Threads (Mounted) 1.25" (M28.5x0.6), 2" (M48x0.75)
    Edge Treatment Unmounted filters are edge blackened
    Usage Warning Not recommended for solar imaging or night visual observation
    Filter Size 1.25" Mounted, 31mm Unmounted, 36mm Unmounted, 2" Mounted, 50mm Unmounted (by variant)

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  • This Antlia filter is covered by a 3-year warranty against delamination.