What is hydrogen alpha photography? It is pretty simple really. Hydrogen gas is almost every where in our galaxy. Most of it just drifts around the galaxy not doing much. If the gas is located close enough to a star that is emitting enough UV light the hydrogen adsorbs the photon which allows an electron to escape the atom. This creates a free electron and a hydrogen ion. The electron and the ion can then recombine and in the process emit a photon. Because the electron is adsorb into a different electronic state the hydrogen emits a photon in the visible range of light. This wavelength is called the Balmer alpha, hydrogen alpha or just HA and is 656.28nm. This is in the deep red part of the spectrum.
To take HA images a filter is placed in front of the camera chip which only passes this specific wavelength. Why would someone want to do this? First, the most sensitive cameras are simple monochrome camera's. If you wish to take color images you must take an image in red, then green, then blue. When you combine those images you get a full color image. Since the HA emission is red astronomers use that wavelength for the red part. There is a second reason we use HA filters. It turns out that most light pollution comes in wavelengths other than HA. By using HA filter we can remove the light pollution from our images. This method also works for moon light! This allows astrophotography to be done during the full moon.
HA photography is displayed in black and white images. If you try to display it in the "real" color the stars would appear red. Stars, being made of mostly hydrogen, also emit this light along with many others. That is why they are generally "white" even in color pictures.
Can you see why it is called the Heart Nebula? Probably a little better than the official name of IC 1805.
The nebula lies some 7500 light years away from Earth and is located in the Perseus arm of the Galaxy in the constellation Cassiopeia. This is an emission nebula showing glowing gas and darker dust lanes. The nebula is formed by plasma of ionized hydrogen and free electrons.
The very brightest part of this nebula (the knot at the right) is separately classified as NGC 896, because it was the first part of this nebula to be discovered. Cick on the image on the right to get a better view.
The nebula's intense red output and its configuration are driven by the radiation emanating from a small group of stars near the nebula's center. This open cluster of stars known as Melotte 15 contains a few bright stars nearly 50 times the mass of our Sun, and many more dim stars that are only a fraction of our Sun's mass. The cluster used to contain a microquasar that was expelled millions of years ago.
The Soul Nebula (a.k.a. the Embryo Nebula, IC 1848). It is an open cluster of stars surrounded by a cloud of dust and gas over 150 light-years across and located about 6,500 light-years from Earth., near the Heart Nebula.
The cluster of stars formed about a million years ago from the material of the nebula. Winds and ultraviolet light from these young stars are excavating a cavity in the cloud. Parts of the cloud that are more dense than their surroundings are being eroded more slowly and form giant towers, or pillars of dust and gas, which all point toward the central star cluster. Material at the interior edges of the cavity is also being compressed by the winds and radiation from the star cluster. This triggers new star formation in those areas. The pillars inside the Soul Nebula are each about 10 light-years tall and have stars forming at their tips.
This was taken using my Megrez 90 and QHY8 camera using my HA filter.
NGC 1499 is commonly known as the California Nebula due to its resemblance to the US state of California. It is a emission nebula locate in the constellation Perseus and is located about 1000 light years distant. The illuminating star, seen in the lower right portion of the image is Xi Persei. The gas we can see is probably not the only gas in the area just the only that is ionized by the star. The top image was taken in 2016 and 2017. The bottom stack was taken on November 1, 2010.
The Jellyfish Nebula is the remnant of a star that went supernova anywhere from 3,000 to 30,000 years ago. Located in the constellation Gemini. It is located near the star Eta Geminorum. Its distance is roughly 5,000 light years from Earth. In this photograph you can see the main shock wave of the supernova detonation.
The Cresent Nebula is in the constallation Cygnus and lies about 5,000 light years distant. It formed when the star in the middle ejected it's outer layers 400,000 years ago. The image actually comes from two shock waves colliding. In this image you can also see emmisions from the surrounding gas.
Taken with an Astro-Tech 8" RC scope and QHY8 Camera on my CGE mount.