Hydrogen Alpha (Ha) photography.
December 27th 2010 10:04
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Colour image of the Orion Nebula M 42
Hydrogen is an element that is found in great abundance throughout the universe.
Most of the hydrogen in the galaxies is found to be in the star . If the hydrogen gas is located close enough to a star that is emitting enough UV light the hydrogen adsorbs the photon this allows an electron to escape the atom, creating a free electron and a hydrogen ion in the process.
The electron and the ion can then recombine causing a photon to be emitted. Because the electron is adsorbed into a different electronic state the hydrogen emits a photon in the visible range of light.
Stars are made up of mostly hydrogen they generally appear as being “white” even when the image is in colour.
A filter is usually placed in front of the camera’s CCD chip this allows only this specific wavelength through the filter.
Orion Nebula M42 Hydrogen Alpha (Ha) image by Carlcan.
The image above is of the Orion Nebula, also called as Messier 42 and M42, is one of the most photographed objects in the nightsky.
This image using Hydrogen Alpha (Ha) filter shows up much more of the nebula's structure.
This bright nebula can be seen with the naked eye.
Most CCD cameras employ a monochrome sensor. If you want to take a colour image then you must use three separate filters red, then green, then blue combining all three separate images you end up with a colour image.
The Ha emission is seen as red. Astronomers use this wavelength to enhance the “red” colour portion of the image, if the image is in monochrome the “red” would appear as “white”.
Astronomers and astrophotographers use Ha filters to cut out most of the light pollution.
Light is reflected differently as conditions change. Our sky on Earth appears blue the sunlight is scattered by our atmosphere to make our sky blue in the daytime.
Reflection nebulas are blue because white light from stars is scattered by extremely small particles of dust in the interstellar space.
Emission nebulas, are very different . They are clouds of glowing gas. They only emit light at discreet wavelengths.
This light comes from atoms in the gas that are ionized by hot young stars that are created from the surrounding gas. That is why Hydrogen Alpha (Ha) offer a better glimpse through the gas cloud to see what’s really there.
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