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Used Antlia 3nm H-alpha Pro Imaging Filter - 31mm

Brand: Used Equipment

SKU : UT-15659

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  • This used item is in "Excellent" condition and comes with original packaging.
  • Minor signs of wear; only noticeable under close inspection. Does not affect function.
  • Unmounted 31mm round H-alpha 3.0nm filter. 
  • Ultra-narrow 3.0nm bandwidths, designed for astroimaging.
  • Made for capturing H-alpha emission nebulas, planetary nebulas, and supernova remnants.
  • High transmission of typically >90%: The filter gives you an enormous contrast boost. It does not brighten deep-sky objects, it blocks unwanted light from other wavelengths and highlights the contrast of the H-alpha band. 
  • Ultra-thin filter cell to minimize vignetting by maximizing possible clear aperture.

Not Recommended:

  • Solar Observing and imaging.
  • Visual observation.
  • Serious eye damage will result if you fail to observe the warning. 

Product Details

  • The Antlia H-alpha Pro 3.0nm filter - 31mm size.

    The Antlia H-alpha 3.0nm filter is suitable for imaging of H-alpha nebulas from both observation sites with light pollution and dark sites as well. It allows only 3.0nm bandwidth high-transmission at a center wavelength of 656.3nm. With an extremely narrow bandwidth, it can effectively improve the contrast of the band at 656.3nm, at the same time it effectively interference the light from other wave bands, especially artificial mercury and sodium lamps.


    Antlia narrowband filters are designed to enhance contrast. Contrast brings out faint features by reducing the background – the narrower the filter, the better.

    Suitable for most emission nebulas, planetary nebulas, and supernova remnants, it can highlight the details of H-alpha contained in these imaging objects well.


    Extremely narrow bandwidth results in a small amount of light, Antlia Filters recommends you use a large-aperture telescope and long exposure time. This will aid to collect enough signal to obtain the details of those faint objects with the H-alpha ultra-narrow filter.

    Blocks other bands:

    The unwanted light from other wavelengths is cut-off, leaving only a width of 3.0nm at 656.3nm, so that you get the highest contrast and your background is increased enormously. This results in an extremely dark background and minimized halos around bright stars. 


    Antlia 3.0nm filters

    In the production process, they use very strict quality control standards. Each filter is individually tested and scanned to ensure that the product meets the parameters they set. It is particularly pointed out that starting from the selection of the substrate, they must control the tolerance of each substrate to a very high standard of +/-0.05mm. As we all know, when light passing through optical materials, it will be refracted and the thickness of the glass will affect the length of light refraction. They allow Antlia filters to achieve parfocal by minimizing tolerance of +/-0.05mm.

    All Antlia narrowband filter edges are blackened. This is critical to minimize stray light for a filter that blocks most light except for the narrow bandpass. As this edge blackening must be hand-made, it becomes very costly to the manufacturer.

    The Antlia Filters cut-off rate has reached a very high technical data point. Many users will be very concerned about how high their filter transmission rate is and ignore the cut-off rate. They keep the signal to >90%T at the 656.3nm line. This makes it stable as the filter becomes spectrally narrower to ensure the best Signal-to-noise Ratio, a cut-off rate of OD3 (0.1%) is required to reduce interference from other wavelengths. It is a very important quality index, and the accomplishment is very difficult. This process requires very high-end equipment, constantly thickens the layers of coating, adds longer production times, and adds more cost to the completed products. 

    Wavelength Graph

    To see the graph, click on the Gallery thumbnail image to expand. Then use [CTRL]-scroll-up for an even closer look.

    Images like Hubble

    Many images of planetary nebula and supernova remnants are taken only with H-a and OIII filters; With an HSO-set of filters (H-alpha, SII, and OIII) you are able to process your images like the ones from the Hubble Space Telescope.

    See the Gallery Tab for an example.  

    Not Recommended:

    • Solar Observing and imaging.
    • Visual observation.
    • Serious eye damage will result if you fail to observe the warning. 

    Technical Data:

    • Schott optical substrate.
    • Surface Quality: 60/40 (Refer to MIL-O-13830).
    • 2 sides fine-optically polished to ensure accurate 1/4 wavefront.
    • 30 arcsec parallelism.
    • Center-Wavelength of Antlia H-alpha 3.0nm filter: 656.3nm.
    • >90% transmission at H-alpha line 656.3nm.
    • >OD3(0.1%)at 300 to 1100nm.
    • 2 sides Multi-layers anti-reflection coating.
    • Single / Non-glued substrate.
    • Ultra-thin filter cell to minimize vignetting by maximize possible clear aperture.
    • Black Anodized Finish.
    • Laser Engraving No Fading.
  • specifications

    Filter ShapeRound
    Filter Size31mm
    Filter TypeH Alpha
  • included items

    • Used Antlia 3nm H-alpha Pro Imaging Filter - 31mm

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