Sunday, January 30, 2011

Sword of Orion on the ST80

The Sword of Orion is a group of open clusters and nebulae located south of Orion's Belt. The most prominent object in the Sword is the Great Orion Nebula, cataloged as Messier 42. The Great Orion Nebula is one of the few nebulae that are visible to the naked eye--the Lagoon Nebula is another.

I once imaged the Sword of Orion with the Epsilon-200, and the results were OK in my opinion. I intend to redo it on the Epsilon-200 when I get a chance. A while back I also imaged the Sword with my ST80 on the EQ-1 mount. Most of the subs were useless, and I only took 30-second exposures. The results were promising, though.

Last week I had the opportunity to re-image the Sword of Orion with the ST80. I used the Vixen GP mount and the Canon EOS Rebel XS camera. I had to take multiple images at different exposure times because the contrast among different parts of the nebulae is so great.  Here is the breakdown of sub-frames:

  • 10x1 second (that is, 10 one-second images)
  • 10x5 seconds
  • 10x10 seconds
  • 10x20 seconds
  • 23x60 seconds
  • 17x120 seconds
I stacked each group of exposures separately, then loaded the six final images as layers in GIMP. I brought out the detail in the brighter parts of the nebulae by using layer masks to cause the shorter-exposure images on lower layers to show through. (If anyone is curious how to do this in GIMP, send me a message and I'll explain in greater detail in another post.)

After the layer masks were complete, I flattened the image and then applied my usual fringe mitigation process.  (Again, e-mail me if you're curious how I remove the purple fringes from the stars.)

Here is the final product:

Sword of Orion, ST80 on Vixen SP, multiple exposures
There are several separately cataloged objects in the Sword. The group of stars on the left edge of the image is an open cluster that is cataloged as NGC 1981. To the right of that is the Running Man Nebula, which is a combination of diffuse nebulae NGC 1973 and NGC 1975, and open cluster NGC 1977. Near the middle of the image is De Mairan's Nebula, which is cataloged as Messier 43. To the right of that is Messier 42, The Great Orion Nebula. (To me, M43 looks like a bird's head, an M42 looks like the bird's body and wings.) Near the right edge of the image is diffuse nebula NGC 1980, which is illuminated by a 2.75 magnitude class B star called Na'ir al Saif (Arabic for "the Bright One in the Sword").

NGC 2362 (Tau Canis Majoris Cluster)

NGC 2362, also cataloged as Caldwell 64, is a tight open cluster of about 60 stars. At its center, from our point of view, is Tau Canis Majoris, a magnitude 4.4 class O supergiant. Tau Canis Majoris is a multiple star system, consisting of at least three stars, and possibly as many as five. The total mass of the system has been estimated at 40 to 50 solar masses! There is apparently some debate as to whether or not this star is part of NGC 2362, but if it is, then at the cluster's estimated distance Tau Canis Majoris is about 50,000 times more luminous than the Sun.

NGC 2362 is also called the Mexican Jumping Bean Cluster because, supposedly, tapping the telescope while viewing the cluster produces an interest effect due to persistence of vision. I only recently found this out, and have not had the opportunity to try it.

NGC 2362 (Tau Canis Majoris Cluster), ST80 on Vixen SP, 9x60


A Big Scary Thunderstorm--complete with heavy rain, lightning and hail--passed over us this evening. Before the rain and hail started, though, I managed to get a few pictures of the lightning from the relative safety of my front door.

Sunday, January 2, 2011

Horsehead and Flame Nebulae

I'm still trying to learn the capabilities of my little imaging setup. The ST80 is an amazing little telescope, especially considering that it's only an achromat. One of the things that I really like about it is that it has a wide field of view, which means that it is possible to see or image fairly large areas of the sky.

Here is an image of several nebulae around the star Alnitak (Zeta Orionis). Alnitak is the easternmost star in the Belt of Orion. Three prominent nebulae in this image are the Flame Nebula, the Horsehead Nebula, and IC 434. Several smaller reflection nebulae dot the area.

Horsehead and Flame Nebulae, ST80 on Vixen SP, 12x180
The star Sigma Orionis is located at the top of the image on the right. This star is visible to the naked eye in most locations. It is located south of Alnitak.

The Horsehead Nebula is a dark nebula, which is an opaque cloud of dust and gas. Located behind it is emission nebula IC 434. The Flame Nebula is being lit up by Alnitak and stars buried within the nebula.

Here is an image of this same area that I made using Sam Houston State University's Takahashi Epsilon-200:

Messier 79

The constellation Lepus, the hare, is located south of the Orion constellation. In some stories, Lepus is being flushed from the grass by Orion's hunting dogs, Sirius and Procyon. Located in the southern part of Lepus is a very unusual sight for this area of the sky: a globular cluster. Most globular clusters are located closer to the core of the Milky Way. There is evidence that suggests that M79 was stolen by the Milky Way from the Canis Major Dwarf galaxy.

Messier 79 is about 40,000 light years away, and is about 118 light years across.

Messier 79, ST80 on Vixen SP, 33x60