What is the wavelength of the OIII filter?
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Wavelength of the OIII Filter
The OIII filter, also known as the oxygen III filter, is specifically designed to pass the light emitted by doubly ionized oxygen atoms, also referred to as O++ or OIII. This filter is widely used in astrophotography and optical astronomy to capture nebulae and other astronomical objects that emit light at specific wavelengths.
The main wavelengths of the OIII filter are centered around 495.9 nm and 500.7 nm. These correspond to the two prominent emission lines of ionized oxygen in space. The OIII filter is instrumental in observing planetary nebulae, supernova remnants, and emission nebulae where OIII emission is strong.
OIII filters usually come in two bandwidth varieties:
- Narrowband: Typically 10 nm or less, focusing on reducing the bandwidth to increase contrast by limiting the amount of other light sources, especially those from light pollution.
- Broadband: Wider than 10 nm, used to capture a broader range of light but with less contrast compared to narrowband filters.
The choice between these two depends on the observer's aim, the lighting conditions, and the type of telescope being used.