• An emission nebula has the reddish color characteristic of ionized hydrogen gas. If a neutral hydrogen atom, H I in astronomical jargon, absorbs sufficiently energetic light, its electron will be stripped away creating an ionized hydrogen atom, or H II. When the ionized hydrogen atom recaptures its electron, it will give off, among other possible colors, a distinctive reddish light. The most likely places to have the makings of an emission nebula, are the gas clouds wherein those young stars are born. Emission nebulae, H II regions and star-forming regions all describe the same sorts of objects. Examples are M42 and M8.
• A reflection nebula has the bluish color of scattered starlight. The dust particles that exist in space are very small. One of the effects of their small size is that they preferentially allow red light to pass but scatter blue light. So, a reflection nebula requires stars and a cloud of dust, but the stars don't necessary have to be so energetic or the stars and dust so intimately related as with an emission nebula. The best example I have is M78, but check out this photo of the Pleiades from the Astronomy Picture of the Day web site.
• Dark nebulae are more common that we might realize or see because, well, they're dark. These are dense clouds of gas and dust that block the light of objects behind them. And precisely because they are dense clouds of gas and dust, they're often, but not always, progenitors of star formation. B86 is an example of a stand-alone dark nebula, and you will spot dark structures and blobs in many of these photos.
• Supernovae remnants are quite different that the other categories mentioned here. Rather than being directly associated with clouds of gas and dust, these are the gas and dust that remain after a star has reached the end of life and, one way or another, exploded catastrophically. An example is M1.

Descriptive information was drawn from The Sky Atlas 2000.0, 2nd Edition by R. A. Strong and R. W. Sinnott with descriptions by W. Tirion and R. W. Sinnott (2000, Sky Publishing Corp. and Cambridge University Press), and Burnham's Celestial Handbook by Robert Burnham, Jr. (1978, Dover Publications, Inc.). North is up and east to the left in all photos. Every effort has been made to display all photos at the same magnification unless otherwise stated.

2010-02-11 White balance = 6000K (Cloudy)
Noise reduction = Off
prime focus (32.5×)
Created from one hundred and twenty 10 s - ISO 1600 photos. I removed a dark frame and flat field from each photo, then enhanced the contrast. I averaged these in groups of ten and removed a residual background. Next, I averaged the resulting images together, removed a background from the red layer only, strongly enhanced the contrast, applied 5×5 Gaussian blur, rotated to north-up, cropped the photo and reduced its size by three. Click the photo to display a larger image in a new window.

This is actually three New General Catalog (NGC) objects: NGC 1973 (nebulosity around the star just above and right of center), 1975 (very faint nebulosity to above and left of center) and 1977 (the three promanent stars and nebulosity below center). The dark lanes separating these three suggest a stylized running figure to some, but that is admittedly difficult to see in this photo. These reflection nebulae and stars are part of the grand Orion star forming region at a distance of 1500 l.y.

2010-02-03 White balance = 6000K (Cloudy)
Noise reduction = Off
prime focus (32.5×)
Created from one hundred and sixty-five 15 s - ISO 1600 photos. I removed a dark frame and flat field from each photo, then enhanced the contrast. I averaged these in groups of eleven, removed a residual background and enhanced the contrast. Next, I averaged the resulting images together in groups of five and enhanced the contrast. I averaged the three "super-groups", enhanced the contrast, applied 5×5 Gaussian blur, rotated to north-up, cropped the photo and reduced its size by three. Click the photo to display a larger image in a new window.

M1, the most easily available supernova remnant for small telescopes, was created from the July, 1054 A.D. supernova. That supernova, bright enough to be visible in the daytime, was recorded by observers around the world including native Americans. M1 is at a distance of approximately 6,000 l.y. implying a physical size of 10.5 l.y. × 7 l.y. but expanding at 990 miles/sec.

2010-02-11
White balance = 6000K (Cloudy)
Noise reduction = Off
prime focus (32.5×)

Created from one hundred and seventy-three 10 s - ISO 1600 photos. I removed a dark frame and flat field from each photo, then enhanced the contrast. I averaged these in 3 groups of ten and 13 groups of eleven. From these groups, I removed a residual background and enhanced the contrast. Next, I averaged the resulting images together enhanced the contrast, applied 5×5 Gaussian blur, rotated to north-up, cropped the photo and reduced its size by three. I replaced the saturated central part of the nebula with the corresponding section of the same picture before the final contrast enhancement was performed. Click the photo to display a larger image in a new window.

M42 is one of the most impressive objects in the sky. Easily visible as part of the sword of Orion, it produces fascinating views by eye, binoculars, or any size telescope. M42 is at the edge of a dark cloud where stars are forming. Some of these young stars have blown a hole in the edge of this cloud forming the nebula.

70´, or 30 l.y. across and 1,500 l.y. away, M42 is primarily illuminated by θ Orionis. The reddish color is hydrogen gas excited by starlight and shining on its own; while the bluish color is starlight reflected off dust in the cloud.

Note the small nebula to the north-east. That is M43 (NGC 1982, de Mairan's Nebula) which is created by the variable star NU Orionis interacting with the cloud of gas and dust from which all these stars are born.

2010-01-13
White balance = 6000K (Cloudy)
Noise reduction = Off
prime focus (32.5×)
Created from three hundred and twenty 15 s - ISO 800 photos. I removed a dark frame and flat field from each photo, then enhanced the contrast. I averaged these in groups of ten, enhanced the contrast and removed the residual background. Next, I averaged the resulting images together in groups of eight and enhanced the contrast. I averaged the four "super-groups", enhanced the contrast, removed a residual background, applied 5×5 Gaussian blur, cropped the photo and reduced its size by three. The slight vertical color variations and striping are the remains of the improperly removed background. Click the photo to display a larger image in a new window.

I spent most of my research career in astronomy observing the gas cloud holding NGC 2024 (at the top of the photograph), so I'm very fond of this object. I'm also very pleased I was able to photograph it because NGC 2024 probably has the lowest surface brightness of any object I'll be able to capture with this equipment under these conditions. NGC 2023, near the bottom of the image, is the brightest of several reflection nebulae in this complex. These are all part of the same interstellar cloud that holds M42, and like M42, are actively forming stars.

This is a rich area for larger telescopes with dark skies … and easy to find because the bright star to the right is ζ Orionis, also known as Alnitak, the eastern-most star in Orion's belt. NGC 2023 and NGC 2024 appear here but there is no sign of IC 434 and the Horsehead Nebula (Barnard 33) which should be in the lower-right of the larger image. Also on the larger image, the brightest stars in the lower-left and upper-right also are just beginning to show their embedding nebulosity. The bright, reddish star in the upper-left of the larger image is the ellipsoidal variable star V1197 Orionis.

Although this photo doesn't do it justice, I believe you'll understand how dramatic a scene this region offers.

2010-02-03 White balance = 6000K (Cloudy)
Noise reduction = Off
prime focus (32.5×)
Created from one hundred and fifty-two 15 s - ISO 1600 photos. I removed a dark frame and flat field from each photo, then enhanced the contrast. I averaged these in groups of eleven, removed a residual background and enhanced the contrast. Next, I averaged the resulting images together in groups of five and enhanced the contrast. I averaged the three "super-groups", enhanced the contrast, applied 5×5 Gaussian blur, rotated to north-up, cropped the photo and reduced its size by three. larger image in a new window.

M78, the larger nebula to the south, is one of the brightest reflection nebula in our sky. As is often the case, other reflection nebulae, created by sister stars involved in the same cloud, appear in the same field. NGC 2071 is the smaller nebula to the north.

M78 is 7´×6´, but only the brightest part is visible in this photo. At a distance of 1,600 l.y., that implies its physical size is more than 3 l.y. across. Through the eyepiece, I can see the two bright stars in M78 surrounded by the faint haze of the very brightest part of the nebula. This makes for an unsettling image of two eyes peering out of a fog in the night.

2009-07-01
White balance = 6000K (Cloudy)
Noise reduction = Off
prime focus using a reducer-corrector lens (52.4×)
Created from the thirty-six best 30 s - ISO 800 photos. I removed a dark frame and flat field from each photo and enhanced the contrast. The modified photos were then averaged them in groups of six, and enhanced the contrast. I averaged the combined images, removed a background, and strongly enhanced the contrast. Finlly, I applied a 7×7 Gaussian blur, rotated to north-up, cropped and reduced the image by a factor of five. Click the photo to display a larger image in a new window.

The Trifid is an emission nebula buried in a reflection nebula much larger than the northern region captured in my photograph. The "tri" in the name Trifid refers to the three (tri) dark, dust lanes which divide the emission nebula into three lobes. About 60 stars are associated with M20. Although it saturated into the appearance of an elongated blob here, the bright "central star" of the emission nebula appears to be four stars in individual photos. Also note the pillars of gas and dust just visible along the southern edge of the emission nebula.

M20 has long been a favorite of amatuers, but it's a challenge for a small telescope. I've glimpsed it from a dark site but never from here in town. I've also made several previous attempts to photograph M20 with no success. But if you fail to spot M20 next time out, don't worry. Sagittarius is rich with other objects.

2009-07-01
White balance = 6000K (Cloudy)
Noise reduction = Off
prime focus using a reducer-corrector lens (52.4×)
Created from the fifty-one best 30 s - ISO 800 photos. I removed a dark frame and flat field from each photo and enhanced the contrast. The modified photos were then averaged into seven groups of seven, the contrast was enhanced and a residual background removed. I averaged the combined images and strongly enhanced the contrast. Finally, cropped and reduced the image by a factor of five. Click the photo to display a larger image in a new window.

To the west (right) of NGC 6520, between the cluster and the brighter, red-tinged star, lies B - for Barnard - 86. One of many dark nebulae cataloged by Edward E. Barnard in the early Twentieth Century, B86 was not discovered by Barnard. That honor goes to Sir William and Caroline Herschel. Caroline noted her brother William's remark, "here is truly a hole in the sky" while scanning this area, and this object was included in their catalog of "vacant places."

Covington lists B86 by Herschel's phrase "Loch im Himmel;" others by "Barnard's Inkspot." With catchy names like that plus the benefits of having another recognizable object in the field and being framed against the Milky Way, I had to make B86 the subject of my first attempt to photograph a stand-alone dark nebula. I think B86 is subtly visible here, but, in the larger image, it is more evident as an absences of stars. Of course the stars are there, but hidden behind the cloud.

2009-07-01
White balance = 6000K (Cloudy)
Noise reduction = Off
prime focus using a reducer-corrector lens (52.4×)
Created from the sixty-eight best 20 s - ISO 800 photos. I removed a dark frame and flat field from each photo and enhanced the contrast. The modified photos were then averaged in nine groups of six plus two groups of seven, and enhanced the contrast. I averaged the combined images into a group of five and a group of six, removed a background, enhanced the contrast. I average the two "super" groups, enhanced the contrast one last time and applied a 7×7 Gaussian blur. Finally I rotated to north-up, cropped and reduced the image by a factor of five. Click the photo to display a larger image in a new window.

The Lagoon Nebula and associated open cluster, NGC 6530, to the east (left) in the photo, are true gems! Visible with the naked eye from a dark site as a small but brighter smudge in the Milky Way, the Lagoon lives up to its name when viewed through a telescope by making one think they're looking into a deep, lagoon of glowing mist. This photo only begins to show its true size. If visible, the entire nebula would fill the photo, and its only a small part of a larger cloud of gas and dust that isn't glowing. M8 is located in the direction of the galactic center so this region is rich for the eyes, binoculars or telescope.

The very brightest spot in the nebula appears to have a small hourglass shape and is often referred to as the Hourglass Nebula despite the fact that there is a beautiful planetary nebula with that name. This structure has been the subject of Hubble Space telescope images. Also note the many darker clouds that help give the nebula its beautiful appearance.

2009-07-18
White balance = 6000K (Cloudy)
Noise reduction = Off
prime focus using a reducer-corrector lens (52.4×)
Created from the fifty-three best 30 s - ISO 800 photos. I removed a dark frame and flat field from each photo and enhanced the contrast. The modified photos were then averaged in one group of five and eight groups of six, and enhanced the contrast. I averaged the combined images, removed a background, and strongly enhanced the contrast. Finlly, I applied a 7×7 Gaussian blur, rotated to north-up, cropped and reduced the image by a factor of five. Click the photo to display a larger image in a new window.

The associated star cluster is obvious in the eyepiece, but I've never seen a hint of the nebulosity and felt I had little hope of capturing the nebula itself. I was pleasantly surprised. Although I'm quite proud of this photo, I admit this image in no way does this M16 justice. Robert Burnham offered the name "Star-Queen Nebula" and called forth imagery of Lovecraft, van Gogh and Tennyson when describing M16. Take a few moments to view the iconic 1995 Pillars of Creation photo from the Hubble Space Telescope, or the truly glorious image of the entire object, Inside the Eagle Nebula taken from Kitt Peak, and you'll quickly see why Burnham allocated so many pages to this object. Both the above mentioned photos are available from the Astronomy Picture of the Day web site.

M16 is 34´ × 27´. At the accepted distance of 5,900 l.y., that implies a size of approximately 50 l.y. for the emission nebula. Of course, the entire gas cloud is much larger. The "eagle" is faintly visible as a dark region just below the center of the picture and seems to be "diving" upon the associated star cluster at the center of the photo. I feel this feature is more obvious in the larger image.

2009-07-18
White balance = 6000K (Cloudy)
Noise reduction = Off
prime focus using a reducer-corrector lens (52.4×)
Created from the fifty-four best 30 s - ISO 800 photos. I removed a dark frame and flat field from each photo and enhanced the contrast. The modified photos were then averaged in six groups of nine, and enhanced the contrast. I averaged the combined images, removed a background, and strongly enhanced the contrast. Finlly, I applied a 7×7 Gaussian blur, rotated to north-up, cropped and reduced the image by a factor of five. Click the photo to display a larger image in a new window.

M17 is bright and beautiful emission nebula and star cluster. With a little imagination, the shape of the swan does appear, admittedly, upside down with the neck to the west (right). This is an impressive and obvious group even from light polluted skies. M17 appears to be about 40´ × 35´. That's bigger than the apparent size of the Moon and would easily fill the entire frame of the photo if the fainter regions were visible. At 5,500 l.y. distance, that means M17 is about 15 × 12 l.y. across, but the entire gas cloud is closer to 40 l.y. in diameter.