Monday, 27 October 2014

Featured Object - The Flame Nebula

The object we'll be looking at this time is the Flame Nebula. This little know nebula is very easy to observe, in terms of its brightness and its size.
The Flame Nebula (NGC 2024) is part of the same expanse of gas that gives us the more well known horse-head nebula. The horse-head nebula is a very faint emission nebula well know because if it's canny likeness to the shape of a horse's head. Both are part of the Orion Molecular Cloud, a star-forming region just below Orion's Belt in the night sky.

The Flame and Horse-head Nebula seen together
with Cluster Camera
The very bight star with the large spike (caused by overexposure) is the reason that these nebulae are visible to us at all. This very bright, blue star shine ultraviolet light into the surrounded gas and dust, energizing it. As the atoms release the absorbed energy, they do so in the form of visible light. producing a glow. This is similar to why we have aurora on the Earth, but on a much larger scale.

The dark shapes and filaments, which are somewhat separate to the bright areas, are between us and the glowing region and block some of this light, producing intricate details.

The Flame Nebula imaged with Galaxy Cam
The bright star is a little bit of a nuisance when it comes to getting a good image. Getting a satisfactory exposure of the nebula means a certain amount of overexposure on the star. This can be reduced by using a H-alpha filter to just show the glowing hydrogen, but at a cost of loosing a lot of reflected light.
A H-alpha filter removes glare from the star.
This image is the result of many exposures stacked together.

Observing tips

  • The Flame Nebula is in the NGC catalogue as NGC 2024
  • An exposure time of 120 000 ms works well on any filter.
  • Use Galaxy Cam for the best detail.
  • BVR (colour) works to give a very colourful image.
  • H-alpha gives a faint, black and white image, but without star glare.
  • Or use Cluster Cam with a Colour or Red filter to capture a larger region.