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What's Up - M 42 the great nebula in Orion

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What’s Up
M 42 the great nebula in Orion

By Steve Coe

So, you wouldn’t think I would start a set of articles about the best objects in the sky without including the Orion Nebula, would you?  I didn’t think so.

If it is winter or early spring in the northern hemisphere then the constellation of Orion is well above the horizon and immediately obvious once you learn what it looks like.  If you are the owner of a new Christmas telescope then the Orion Nebula is one of the first things you will find in the sky.  It is easy to see just below the Belt of Orion.

A little study and you will find that there are stars starting their life within the nebula right now.  This nebula is 1500 light years away, so we are seeing it as it was 1500 years ago, just after the fall of the Roman Empire.  But, nebulae don’t change very quickly on the human scale, so it is very similar to what our ancestors would have seen.

The stars involved within the nebula are a fascinating collection.  The bright Trapezium of four bright stars and several fainter companions are illuminating the gas within the nebula so that it literally glows in the dark.  The dark “Fishmouth” area is near the Trapezium stars and it is a nebula that blocks off the glow of stars and gas that are behind it.  There is also a reflection nebula aspect to M 42 so the starlight bounces off dust particles and then the light makes its way to Earth.  There is much to see in this famous cloud of gas, dust and stars all intermingled.

One other reason this is such a famous and well observed nebula is that it is at a declination of negative 5.5 degrees.  This means that virtually all the observers of the sky on Earth can view the Orion Nebula when it is far above the horizon and available to clear skies.

For almost 20 years I was the leader of the Novice Group within the Saguaro Astronomy Club in Phoenix.  One of the things I spoke often is that “there is no such thing as a general purpose telescope”.  That is because this is not a general purpose Universe.  It takes high power to enjoy the Moon and planets.  A wide field telescope or binoculars will provide the best views of the Milky Way and large deep sky objects.  Lots of aperture is necessary to really enjoy most deep sky objects.  You just can’t do it all with one type of telescope.  The Orion Nebula can be enjoyed in a variety of optical aids because it is large, detailed and bright.  I hope that my observations will prove that point.

Using a TV 102, a four inch refractor, on a good night provides a “wow” view if there ever was one.  With a wide 27mm Panoptic eyepiece the entire nebula is visible and there is more glowing gas both above and below the main nebula.  I can see ten stars involved within the glow even at this low power.  Moving up to a 14mm eyepieces presents the nebula as very bright, very large and shows that very irregular figure with excellent contrast.  The dark "Fish Mouth" feature is easily seen with good contrast and there are 4 stars within the Trapezium with this magnification.  The mottling within the bright area around the Trapezium is easily seen.  Raising the power with a 4.7mm eyepiece shows 6 stars in the Trapezium, the final two are somewhat faint and difficult.

One of my favorite telescopes which I have owned over the years was a 6" f/6 Maksutov-Newtonian.  I am still sorry I sold it off to this day.  On a fair night at 40X with a 22mm Panoptic there are 21 stars involved in this nebulosity, including the 4 seen in the Trapezium.  All four nebulae fit in this field; M 43, M42, NGC 1980 and NGC 1973, which includes Iota Ori.  A spectacular object with many subtle changes in brightness and form.  Light and dark areas intertwine and the entire loop of nebulosity is seen, up and over the bright area of the Trapezium.  Adding the UHC filter makes the nebula have more contrast, but gets rid of some subtle variations and delicate star groupings, I like the un-filtered view better.  Raising power with the 14mm UWA eyepiece shows off some of that delicate structure better and the dark "Fish Mouth" area near the Trapezium is more contrasty.  Going to the 8.8mm UWA shows off several orange stars in the nebula and splits the Trapezium, the E and F members are glimpsed 20% of the time.  All in all, a "WOW!" object, first class.

Using the late Pierre Schwaar’s 20" f/5 at a location in SW Arizona near Sentinel, Arizona, the two of us had a terrific night.  Pierre and I got away for several days before New Year's Day of 1995.  Years before I had purchased a giant sized 38mm Erfle eyepiece at the Riverside Telescope Makers Conference.  It shows lots of detail in the "wings" above the Trapezium.  These beautiful curved glowing lanes of nebulosity are light red (I refuse to say pink) and obviously brighter than the background glow.  Forty stars are involved within the nebula at this low power, some of them are orange in color.  Moving up to high power with the "brand new" 6.7mm Ultra Wide the central area is fabulous.  The southeast side of this area is a straight line with bright nebulosity defining the transition from the inner region and the outer fainter nebula.  The nebulosity around the Trapezium is still very bright even at high power and is very mottled.  Several curved lanes of light and dark nebulosity surround the Trapezium and there are a dozen stars involved beyond the Trapezium.  This part of the nebula is a light green color, much like a planetary nebula.  The dark Fish mouth has scalloped edges and a small amount of glowing nebulosity within this dark area.  The three bright stars to the east of the Trapezium have several striking orange stars involved near them.  There is another grouping of orange and light orange stars to the south of this area, just at the edge of the field of view.  Off to the northwest of the Trapezium is a prominent, but thin, dark lane that stops at the area of the bright nebulosity around the Trapezium.  So, this dark lane is perpendicular to the Fish mouth.  All in all, a fascinating and famous region; Pierre and I would look and then rest for a moment and then look again at this scene.  It did not take long to climb the ladder knowing the view that was awaiting. 

Sword of Orion  135mm f/2.8 lens  6 min
Canon Xt with Hutech modification
800 ISO setting

Orion Nebula  300mm f/4 lens  3 min exposure
Canon Xt with Hutech modification
ISO 800

Trapezium area of M 42 
32” f/4.75 Newtonian at 385X  no filter
Antennas site  Seeing=7/10  Transparency=8/10


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