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The Dish Cluster, the Pencil Nebula, and spiral galaxy NGC 2655

February 25–March 3, 2016: The Dish Cluster in Puppis offers small-telescope owners a nice view, while large-telescope owners can seek out the Pencil Nebula in Vela and spiral galaxy NGC 2655 in Camelopardalis.
Puppis
The Dish Cluster (NGC 2539) lies in the far northern part of the constellation Puppis.
Astronomy: Roen Kelly
Each week, Astronomy magazine Senior Editor Michael E. Bakich, a master at explaining how to observe, posts a podcast about three or more objects or events you can see in the sky.

Targets for February 25–March 3, 2016

Small telescope: The Dish Cluster (NGC 2539)
Large telescope: The Pencil Nebula (NGC 2736)
Large telescope: Spiral galaxy NGC 2655

A tasty morsel
This week’s small-telescope target is the Dish Cluster in the constellation Puppis the Stern. It also goes by the designation open cluster NGC 2539. It shines at magnitude 6.5 and measures 21' across.

This target sits nearly 8° east-southeast of magnitude 3.9 Alpha (α) Monocerotis. When you move into the area, look for the yellow-white magnitude 4.7 star 19 Puppis. NGC 2539 sits less than 12' to the west-northwest.

The Dish Cluster gets its common name from a description of NGC 2539 by Astronomy magazine Contributing Editor Stephen James O’Meara. He sees the oval shape of a dish formed by the brightest stars of this cluster when he observes it at a magnification of 23x.

A 4-inch telescope shows 75 stars between 9th and 13th magnitude, while a 10-inch scope reveals more than 100 stars. The brightest appear clumped in an oval a bit south of center that stretches east-west.

Take notes
This week’s first large-scope object is the Pencil Nebula (NGC 2736) in the southern constellation Vela the Sails. To find it, look 2.9° south-southwest of magnitude 2.2 Lambda (λ) Velorum.

The Pencil Nebula forms a small part of the Vela supernova remnant. Amateur astronomers dubbed this object the Pencil because, through a telescope, it appears long, straight, and one end looks “sharpened.” It measures about 20' long.

British astronomer Sir John Herschel (1792–1871) discovered the Pencil Nebula in 1835 while he was staying in South Africa. He described it as “an extraordinary long narrow ray of excessively feeble light.” Based on that description, astronomers also call NGC 2736 Herschel’s Ray.

The Pencil Nebula measures about three-quarters of a light-year across, while the Vela supernova remnant spans 114 light-years. The remnant lies about 815 light-years away from Earth.

The best way to observe the Pencil Nebula is to use a 12-inch or larger telescope with a low-power eyepiece to which you’ve attached a nebula filter, such as an Oxygen-III. Either disengage your telescope’s drive motor or set its slewing speed at “medium,” and scan the area.

Where, exactly?
This week’s second large-telescope target is spiral galaxy NGC 2655 in Camelopardalis the Giraffe. This object effectively sits in the middle of nowhere, so I hope your telescope’s drive is a go-to. If not, you’ll find it 13.5° northwest of magnitude 3.8 Lambda Draconis, which lies in Draco the Dragon.

NGC 2655 glows at magnitude 10.1 and measures 6.0' by 5.3'.

Through small telescopes, you won’t see much of this bright galaxy except an evenly illuminated face and an oval shape. It’s 50 percent longer than it is wide, stretched in an east-west orientation. A 12-inch scope at a magnification of 200x or above shows a bit more: NGC 2655’s central region is brighter, and a thin outer halo surrounds it.

Expand your observing at Astronomy.com

The Sky this Week
Get a daily digest of celestial events coming soon to a sky near you.

Observing Basics
Find more guidance from Senior Editor Michael E. Bakich with his Observing Basics video series.
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