Quote:
Originally Posted by BilliGoatsGruff
What do we look for when hunting nebula? I thought I might give it a go, but have no idea what to look for. Are there any in the southern sky worth hunting down? What magnification is recommended for doing so?
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Hello Billie,
Nebulae through a scope look like soft glowing smoke. That is the best way I have to describe them. And just like smoke, they are 3D structures even though the may appear flat. And also like smoke, these structures can be quite prominent or ever so soft and faint.
Because they are smoke like, they can be of any shape, size and brilliance. In many instances they can be like angel's breath faint, when you might just be looking for the vaguest of difference in shades of black to make out the nebula - the Horsehead nebula is like this. Others very bright with so much going on it is an extraordinary place - Eta Carina nebula.
Before I continue with mentioning other nebulae, it is a good idea be have some idea of what a nebula is and what is happening within them. This way when you look at ANY nebula, you can understand exactly what is happening to make each individual one glow the way it does, and recognize structures that you see and what forms them. This will help you actually SEE MORE because you now have a more educated outlook.
The best way I have to show you the mechanisms of nebulae is with a link to a fabulous Hubble site of Eta Carina. The nebula is so complex, this site is fantastic resource to understanding nebulae. It will take you through the many different structures within it and what is causing them. Even though it doesn't talk about Planetary nebulae or super nova remnants, it does explain the reasons for why they glow:
Hubble Tour of Eta Carina Nebula
I've also attached sketches I've done of the various nebulae I'll be mentioning to give you an idea of how these look through a scope. These have been done using different sized scopes, and even binos, and from dark sites and from my home in Sydney, so you can get a feel for what can be seen even under light polluted skies.
Eta Carina with a 4" scope from a dark site:
Eta Carina with a 17.5" scope from my home in Sydney:
Other nebulae to explore:
* Pan your scope around the area of Eta Carina, as far east as the Southern Cross and all around Eta. There are dozens of nebulae and clusters to discover here. Some nebulae and cluster groups form delightful strings of structures that are best appreciated with low power in a scope or with binos.
Area around Eta Carina with binos from Sydney:
* M8 and M20 in Sagittarius. The Lagoon and Trifid nebulae are an outstanding pair. The Lagoon is an emission nebula powered by a cluster of massive stars, while the Trifid is combination of reflection and emission. In my 17.5" I see a soft violet colour to the Trifid! But, I also adore this pair in binos and in my 8" f/4 scope where the two fit within the one field of view at low power!!! The little star cluster M21 also fits in the FOV. What makes low power a must here is that surrounding this trio is the mottled structure of the Milky Way and many finger-like dark nebulae. Just delightful.
Lagoon and Trifid with an 8" scope from Sydney:
* M17, the Swan or Omega nebula. This bright nebula is much more massive than just the bright part that we see. Its extensions are just enormous and require patience and time to follow these tendrils. I also find the crook of the swan's neck staggering as it is 'blacker' than the surrounding Milky Way, meaning that there is a lot of dark material there obstructing the background glow.
Swan with a 17.5" from a dark site:
* M16, the Eagle. This nebula is bright, but the 'Eagle' structure is very difficult to see and requires a large aperture to make out visually. So fickle is the Eagle that if seeing conditions are not good it will elude detection too.
Eagle with a 17.5" from a dark site:
All of these above four nebulae are naked eye objects too.
* Mentioned by CJ is the wonderous Tarantula nebula in the galaxy the Large Magellanic Cloud that is orbiting our Milky Way galaxy. It is visible naked eye as a spur on one end of the main bar that forms the LMC. This nebula takes magnification really well so its fiberous structure can be followed. The LMC is also surrounded by literally dozens of other nebulae and clusters. Even a short sweep of one's scope around the Spider will reveal so many of these! This is one very busy place the LMC! It alone contains hundreds of open and globular clusters, and emission, reflection & planetary nebulae, and supernova remnants.
Tarantula with a 17.5" from a dark site:
* M42, the Great Orion Nebula. Even though the view of it from this time of the year in late May is only brief, it is still a worthy target. Its power comes from the intense tiny cluster the Trapezium. The Trapezium is easy to make out into its main four component stars, Trap. A, B, C & D. A 5" scope and larger will show Trap E and F. Very large apertures will show under very good conditions Trap G, H & I. M42 also holds the easiest dark pillar to see in the whole sky. The "Fish Mouth" is a dark pillar hiding a cluster of proto-stars that are about to kick off their nuclear fire. Evidence for this cluster is that there must be something massive hidden within the pillar that is able to hold onto gas and dust to resist the erosive power of the energy pumped out by the Trapezium. Hubble views of the pillar reveals these proto-stars glowing in the infrared specturm. M42 is a heck of a lot busier than we think of at first...
M42 with an 8" scope from my home in Sydney:
How to view nebulae:
Start with your lowest power to first spot the likely candidate. Then you can change your eyepieces to see what more or less magnification offers. You can also use Oxygen 3 (OIII) or Ultra High Contrast (UHC) filters to help bring out the nebulae by toning down the continuum of sky glow to just allow very specific wavelengths of light at which these objects glow to be transmitted. Averted vision with many of these nebulae is you best tool as well.
Should get you going for a while...
Mental.
Finding it is easy. Do you have charts and binos? Can you find the Southern Cross? It's near the cross and visible in binos.
that stuff stumps me.
I found the tarantula nebula a while ago, but it was fainter than I expected.
