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Constellations: Monoceros -- The "One Horned"


While usually associated with the unicorn, a legendary creature, the constellation itself is "modern." Formed in 1624 by the German astronomer Jakob Bartsch, the unicorn probably originated from descriptions of the Indian rhinoceros.


Each map can be clicked on to produce a 916x1200 version of it. They sport red labels, which look good on screen, but which disappear when used with red flashlights. Each map, therefore has a second link to a map better suited for printing in a graphics program, and using in the field. While they are quite large, they are all about 40-60k, and so are easy to view at today's modem speeds. The first map is a wide area view of the constellation, suitable for naked eye browsing. The next views are binocular width, showing stars to mag. 10, and labeling deepsky objects to magnitude 12.

Interactive, wide area map of Monoceros

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Click the map for a 916x1200 version of the above. Click here for a map better suited for use in the field.

Eastern Section

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This is the eastern section of the constellation. The map displays stars to magnitude 10, and deepsky objects to magnitude 12. Click here for a map better suited for use in the field.

Western Section

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Click here for a map better suited for use in the field.


Image thumbnail 60k JPEG NGC2506 (Bennett 39, Caldwell 54) is a mag. 7.6, pretty large (7') very rich open cluster of about 150 stars from mag. 11-20. It sits in the south-east corner of the constellation. From the Digital Sky Survey.
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Image thumbnail 93k JPEG Steve Coe, borrowing from the NGC description, writes this: "NGC2353 is pretty bright, pretty large, pretty rich and not compressed. It is a nice cluster at 135X, with about 50 members. The UHC filter will just barely show a very faint streamer of nebulosity on the south side. Rocking the scope helps to make the nebula more noticeable."

You find the cluster 3.4° SE of M50. From the Digital Sky Survey.
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Image thumbnail 94k JPEG M50 (NGC2323) is an open cluster in south-central Monoceros located between Sirius and Procyon. Dreyer describes the cluster as rich, and very large (16'). Overall brightness is mag. 5.9. Individual stars range from mags. 9-14.
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Image thumbnail 67k JPEG Image thumbnail 4k GIF
NGC2301 is a mag. 6 open cluster, consisting of about 80 mag. 8 stars and fainter. Jere Kahanpää describes it as "A beautiful cluster. The most striking detail is a chain of bright stars running from the center towrds S. Centered on a nice double star, components blue/yellow. About 20 stars [were drawn]. Some of the fainter stars were not drawn as many other observers wanted to see and draw the cluster too."

The cluster is located 5.1° WNW of Delta Monocerotis. The first image appears to be a Digital Sky Survey image taken from Le super NGC Catalogue! The second image is a drawing by Jere Kahanpää.
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Image thumbnail 39k JPEG Image thumbnail 70k JPEG
NGC2264 refers to the Cone Nebula, a bit of emission nebulosity at the tip of the Christmas Tree Cluster (at the bottom of both images). A 12" should allow a glimpse. Nebula filters help. The cluster itself is NGC2265. It looks like a Christmas tree, and is quite pretty with its 30, or so 12 to 13 mag. stars. To find it, draw a line from Bellatrix through Betelgeuse. Extend it 1.5 times that separation past Betelgeuse. Then move a degree north. The color image is by David Hanon, using an Astro-Physics 7", f9 refractor and an SBIG ST8. The second image is from the Digital Sky Survey.
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Image thumbnail 22k JPEG NGC2261 (Best 69, Caldwell 46) is a bright (brightness averages mag. 10, it varies) elongated (2'x1' in PA 330, i.e. almost north to south) patch of nebulosity around the star R Monocerotis near the north-west border of the constellation.. The star R itself is harder to spot. From the Digital Sky Survey.
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Image thumbnail 93k JPEG Collinder 106 is a mag. 4.6 open cluster, about 45' in diameter, and consisting of about 20 stars, and located about 1°50' NE of the Rosette Cluster. The brightest star in the cluster is Plaskett's Star, a massive binary system.
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Image thumbnail 93k JPEG NGC2251 is in the upper, left of the photograph. The mag. 7.3 open cluster is described as very large (10'), extended, rich (30 stars at mag. 9.1 and fainter), and with little condensation. It is found 2.2° south-west of the Christmas Tree Cluster.

The smaller cluster 46' to the SSE is NGC2254. Dreyer says it is small, fairly condensed, irregularly shaped, and possesses about 50 stars from mags. 11-13. Overall magnitude is 9.7. Both this and NGC2251 are located 10.1° east of Betelgeuse. From the Digital Sky Survey.
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Image thumbnail 91k JPEG Image thumbnail 130k JPEG

NGC2244 (Best 68), and NGCs 2237, 2238, and 2239 (Caldwell 50-49) forms the Rosette Cluster and Nebula. Finding it is not easy. One method involves scanning just north of a line drawn between Meissa (Lambda Orionis) and Betelgeuse (Alpha Orionis). Extend the line to the ESE 1.5 times the distance between the two stars. Visually, this is an open cluster with some vague grayish areas, especially off the the west. Dreyer calls this a scattered cluster. Then he abandons his cryptic abbreviations to call it beautiful. Photographs show a stunning ring of nebulosity extending over 2° of sky. Best view the nebulosity with a 50-80mm finder equipped with an OIII filter.

Image on the left consists of 9, 1° downloads from the Digital Sky Survey, stitched and slightly cropped. Image on the right by Jason Ware. Taken with a 6" refractor on 4x5 film.
Map Printable Map 1.1 meg. version


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