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Home > Filters > Nebulae filters > OIII Filters > Astronomik > MFR > Astronomik Filters OIII CCD Filter, SC

Astronomik Filters OIII CCD Filter, SC

Product no.: 43812
Manufacturer: Astronomik

€ 319.00

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Astronomik Filters OIII CCD Filter, SC
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Product description:

Bring Out The Faint Structures In Nebula

Narrowband filters set a new bar of performance and durability for imaging and research

They enhance contrast of emission targets by lowering your background signal. The guaranteed >90% transmittance at the emission wavelength provides you with the highest signal available. Narrowband filters are renowned for minimizing halos around bright stars, even for long exposures of 30-45 minutes typical of narrowband imaging in astrophotography. Lastly, Narrowband filters are coated to the edge of the part and are edge blackened. This is critical to minimize stray light for a filter that blocks most light except for the narrow bandpass.

Narrowband filters for imaging are all about contrast. What do we mean by this? Contrast brings out faint features by reducing the background – the narrower the filter, the better. The problem is keeping the signal (%T at the emission line) constant as the filter becomes spectrally narrower. This is why our >90%T guarantee is so important, even though it becomes very costly to manufacture. But, this assures you that you can take advantage of the improved contrast with our narrower filters compared to the much less expensive 7- 8.5 nm filters on the market. You can see the increase in contrast in the sequence of equal-exposure images of the Crescent Nebula (NGC 6888) taken on the same system and on the same night. As the bandwidth becomes narrower, the nebula “pops” out of the background, as does the faint surrounding nebulosity. Actually, the >90%T is a legacy specification, since new production technologies employed over the past 3-4 years routinely produces 97-98%T at the emission wavelengths.

In contrast to purely visual filters, photographic CCD filters have built-in IR-blocking, which prevents the optical problems caused by infrared radiation.

How do I interpret these transmission curves?

  • the wavelength is plotted in nanometers on the horizontal axis. 400nm corresponds to deep blue, 520nm to green and at 600nm to red
  • transmission, in %, is plotted on the vertical axis
  • visual filters: The gray curve shows the relative sensitivity of the dark adapted human eye at night
  • photographic filters: The gray curve shows the relative sensitivity of a typical CCD sensor
  • orange: the main emission lines which contribute to artificial sky glow, e.g lines from mercury (Hg) and sodium (Na)
  • green: the most important emission lines from nebulae, such as the lines from hydrogen (H-alpha and H-beta) and the lines from oxygen (OIII)

19.01.2020
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