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Antlia CH4 Methane Filter - 1.25"

Antlia CH4 Methane Filter - 1.25"

by Antlia
SKU ANT-CH4
CA$236.00 - CA$236.00
CA$236.00
CA$236.00 - CA$236.00
CA$236.00
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  • Isolates the 889nm methane absorption band for planetary imaging
  • 20nm wide bandpass centered at 889nm, in the near infrared
  • Average transmission above 90%, with 90% transmission at 889nm
  • OD5 (0.001%) blocking from 200-1050nm suppresses unwanted signal
  • Both sides fine-optically polished to an accurate 1/4 wavefront
  • Standard 1.25" (M28.5x0.6) threaded cell
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • Antlia CH4 Methane Filter - 1.25"

    The Antlia CH4 Methane Filter passes a 20nm wide band of near-infrared light centered at 889nm, where methane absorbs strongly. Antlia developed it to show finer details and more contrast of the methane in planetary atmospheres, and recommends it for imaging Jupiter, Saturn, Mars and the other planets. Average transmission is above 90%, with OD5 (0.001%) blocking from 200-1050nm.

    Imaging at 889nm: Isolating Methane Absorption Bands

    This filter transmits light in a narrow 20nm window around 889nm, a wavelength where methane gas strongly absorbs light. When you image Jupiter or Saturn, regions where sunlight travels deeper through methane appear dark, while high-altitude clouds and hazes, and moons reflecting sunlight, appear bright. The result shows atmospheric structure differently from visible light, with more contrast in the methane band.

    1/4 Wavefront Optics for High-Resolution Planetary Data

    The Antlia CH4 filter is fine-optically polished on both sides to an accurate 1/4 wavefront, with 30 arcsecond parallelism and multi-layer anti-reflection coating on both sides. It sits in an ultra-thin, black anodized 1.25" cell designed to minimize vignetting by maximizing the clear aperture.

    • Deep Blocking (OD5): Light outside the passband from 200-1050nm is blocked to OD5 (0.001%), that is 1/100,000.
    • Single Substrate: The filter is built on a single, non-glued optical substrate, 2mm +/-0.05mm thick.

    Requirements for the 20nm Bandpass: Longer Exposures & Larger Apertures

    The human eye is not sensitive to light beyond about 700nm, so no one can see what this filter transmits, and it is not suitable for visual applications. Because methane absorbs strongly in this 20nm band, little light reaches the sensor: to produce good results you are likely to require relatively longer exposure times and a larger aperture telescope than with other filters.

  • What details can the Antlia CH4 Methane Filter reveal on Jupiter?

    Antlia developed the CH4 filter to show finer details and more contrast of methane on planets such as Jupiter. In methane-band images, high-altitude features such as the Great Red Spot and the polar hazes typically appear bright, while regions where light penetrates deeper appear dark.

    Why can't I use the Antlia 889nm Methane Filter for visual observing?

    The human eye's sensitivity ends around 700nm. This filter transmits light at 889nm, which is deep in the near-infrared portion of the spectrum. No one can see what is transmitted by this filter, so it is not suitable for visual applications. It is for imaging with a camera.

    What kind of telescope is best for the Antlia CH4 Filter?

    To produce good results you are likely to require a larger aperture telescope with this filter than with other filters, along with relatively longer exposure times. No minimum aperture is given.

    How does the Antlia Methane Filter's 20nm bandpass affect my exposure times?

    A 20nm band at a wavelength that methane absorbs passes far less light than a broadband luminance or IR-pass filter. You are likely to require relatively longer exposure times with this filter than with other filters, so plan on longer exposures or higher gain.

    Is the Antlia CH4 filter parfocal with other 2mm filters?

    The substrate thickness is 2mm +/-0.05mm, but parfocality is not specified for this filter. Filters of the same thickness usually need less refocusing when you switch between them, but check focus after each filter change.

    Can I use the Antlia CH4 filter for imaging the Sun?

    Warning: This filter is not a solar filter, and you must never look at the Sun with it. CH4 filters are not for visual use. For solar imaging, an energy rejection filter must be used with the Methane Filter, otherwise the heat can be sufficient to damage the telescope, the Methane Filter and the imaging system. Contact us before attempting solar imaging with it.

  • Filter Type Methane (CH4) planetary filter, near infrared
    Central Wavelength (CWL) 889nm
    Bandpass 20nm
    Transmission Tave >90%; 90% at 889nm
    Blocking OD5 (0.001%) @ 200-1050nm
    Wavefront Accuracy 1/4 wavefront
    Parallelism 30 arcsec
    Filter Thickness 2mm +/- 0.05mm
    Substrate Optical, single / non-glued
    Coatings 2-sided multi-layer anti-reflection
    Surface Quality 60/40 (MIL-O-13830)
    Filter Size 1.25" Mounted
    Filter Ring M28.5x0.6 thread, ultra-thin, black anodized
    Primary Use Planetary imaging of Mars, Jupiter, Saturn
    Not Suitable For Visual applications
    Solar Warning Not for visual use; without an energy rejection filter, heat can damage the telescope, the filter and the imaging system

    • Antlia CH4 Methane Filter - 1.25"

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  • Contact us for warranty details.