Astronomik H-beta Filter

Astronomik H-beta Filter 1,25" (M28.5)

Astronomik H-beta Filter 1,25" (M28.5)
Astronomik H-beta Filter 2" (E48)
Astronomik H-beta Filter 31mm, unmounted
Astronomik H-beta Filter 36mm, unmounted
Astronomik H-beta Filter 38mm, unmounted
Astronomik H-beta Filter 50mm, unmounted
Astronomik CLS EOS Clip-Filter
Astronomik H-beta Filter SC Rear Cell (2" / 24TPI)
Astronomik H-beta Filter T-Mount (M42x0,75)
Astronomik H-beta Filter Transmission Curve

Click the image for full resolution

The Astronomik H-beta is a filter for visual observation, in particular with instruments of larger aperture.

It lets the light of the H-beta emission line pass nearly unhindered and blocks the remaining spectral range to the extent that the eye is dark adapted. By the use of the Astronomik H-beta filter, the contrast is increased so strongly, that even the observation of the Horse Head Nebulae with telescopes of 10" - 12" reaches the realm of the possible.

Main use

The optimal aperture ratio for the use of the filter is 1:4,5 to 1:6. The range of application extends from 1:3.5 to 1:15. Transmission losses and chromatic distortions, which arise with other filters, are only apparent with the Astronomik filters when extremely fast aperture ratios of 1:3 and higher are used. The Astronomik H-beta filter will allow you to view large objects, in the whole field of view of the eyepiece, even when using wide-angle eyepieces - not only in the center of the eyepiece. This filter should be used on telescopes with a diameter of 8 " (20cm) or larger. Smaller instruments do not gather enough light for meaningful and satisfying astronomical work. Due to the high optical quality of the Astronomik H-beta filter substrate you will see the same needle-sharp stars as you would from your regular telescope.

Other uses

  • In the whole sky, there are few objects that benefit from the use of this filter in visual observation. On the other hand h-beta filters often decide about seeing or not seeing an object. Without a filter the eye is hardly able to discover the low contrasts of H-alpha regions.
  • With EOS Clip Filter even in extreme light polluted areas photography with DSLR cameras becomes possible.

more information about the visual Astronomik filters


How to read the chart
  • The horizontal axis is the Wavelength in Nanometers (nm). 400nm is deep blue, at 520nm the human eye senses green and at 600nm red. At 656nm is the famous "H-Alpha" emission line of hydrogen.
  • The transmission in % is plotted on the vertical axis.
  • The red line shows the transmission of the filter.
  • Visual filters: The grey line in the background shows the relative sensitivity of the human eye at night. The maximum is at ~510nm and drops to longer and shorter wavelengths. You can easily see, that you can´t see anything of the H-alpha line at night (even if you can during daylight!) The sensitivity at 656nm is 0% at night!
  • Photographic filters: The grey line in the background shows the sensitivity of a typical CCD sensor.
  • The most important artifical emission lines are shown in orange. The artifical light pollution is dominated by see mercury (Hg) and sodium (Na), which are used in nearly all streetlights.
  • The most important emission lines from nebulas are shown in green. The most important lines are from ionized Hydrogen (H-alpha and H-beta) and double ionized oyxgen (OIII).

The major emission lines of artifical light pollution:
| Hg 435,8nm | Hg 546,1nm | Hg 577,0nm | Hg 578,1nm |
| Na 589,0nm | Na 589,6nm | Na 615,4nm | Na 616,1nm |

The major emission lines of nebulas:
H-β 486,1nm | OIII 495,9nm | OIII 500,7nm | H-α 656,3nm


  • Visual observation (dark skies): Very good, but only suitable for a few objects
  • Visual observation (urban skies): Unsuitable
  • Film photography: It depends, very long exposure time
  • CCD photography: Good, when used with an additional IR-block-filter
  • DSLR photography (original): Very good, but only suitable for a few objects
  • DSLR photography (astro modified): Very good, but only suitable for a few objects
  • DSLR photography (MC modified): Good, when used with an additional IR-block-filter
  • Webcam / Video (Planets): Unsuitable
  • Webcam / Video (Deep Sky): Unsuitable

Technical Data

  • typ. transmission of better then 95% at the H-beta line
  • complete blocking of all disturbing wavelengths
  • Main operational use: Hydrogen Nebulae
  • No moisture (humidity) sensitivity, no aging, and totally scratch-proof
  • Excellent carrier material - substrate is optically polished. The optical performance (resolution & contrast) of your telescope is not reduced in any way by the filter.
  • Parfocal with other Astronomik filters
  • Glass thickness: 1mm
  • Completely resistant against high humidity, scratches and aging effects
  • Diffraction limited, the filter will not reduce the optical performance of your telescope!
  • Astronomik filters are delivered in a high-quality, long lasting, filter box

The filter is available in the following sizes

Filter displayed products below by their features
  1. Hß (486nm) (4)

H-beta Filter

  1. Astronomik H-beta visual 1,25'' (M28,5)

    Astronomik H-beta visual 1,25'' (M28,5)

    excl. VAT (Non-EU): €83.19 incl. VAT (EU): €99.00
  2. Astronomik H-beta visual 2'' (M48)

    Astronomik H-beta visual 2'' (M48)

    excl. VAT (Non-EU): €167.23 incl. VAT (EU): €199.00
  3. Astronomik H-beta visual T-Mount (M42x0,75)

    Astronomik H-beta visual T-Mount (M42x0,75)

    excl. VAT (Non-EU): €167.23 incl. VAT (EU): €199.00
  4. Astronomik H-beta visual SC Rear Cell (2'' / 24TPI)

    Astronomik H-beta visual SC Rear Cell (2'' / 24TPI)

    excl. VAT (Non-EU): €192.44 incl. VAT (EU): €229.00

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