Archive for March 2018

NGC 2371-72 Planetary Nebula in Gemini – March 2018 Observer’s Challenge Report #109

March 29, 2018

Observer’s Challenge Report #109:  

MARCH 2018 OBSERVERS CHALLENGE – NGC-2371-72

Pencil sketch using a 10-inch reflector with inverted colors.  

Rogers NGC-2371 Inverted

NGC 2371-2372, Planetary in Gemini, nebula magnitude 11.3; central star 14.8.

This planetary is easy to discern with 10-inch reflector from my moderately light polluted backyard. At low power (57x) the planetary appears as a faint and small elongated nebulous patch.

When increasing the magnification to 207x, and with a UHC narrowband nebula filter, two distinctive lobes become visible, connected by a faint haze. The nebula is oriented NE-SW, with the SW lobe being brighter and having greater concentration. The bright spot becomes visible using averted vision, located on the NW side of the westernmost lobe.

When first observing this planetary almost twenty five years ago, I mistakenly thought this bright spot to be the 14.5 magnitude central star. It was, however, during a later observing session in 1998 that I realized the bright spot was not centrally located and far too bright to be the extremely faint central star. Another observation the following year confirmed this.

NGC 2371-72 has a similar appearance, but not nearly as bright as M76 (NGC 650-1) planetary nebula in Perseus.

Roger Ivester

 

NGC 2371-72
By Dr. James R. Dire

My image of NGC 2371/2 was taken with an 8-inch f/8 Ritchey–Chrétien Cassegrain with a Televue 0.8x focal reducer/field flattener yielding f/6.4. It was captured with an SBIG ST-2000XCM CCD camera and the exposure was 2.5 hours.

James NGC-2371

The planetary nebula has what appears to be a regular elliptical shell, divided into two main segments by a dark major-axis lane. The bright lobes are thought to be from bipolar flow from the central star. The cyan colored emissions come from O-III atoms. My image picked up two outer blue arc, most likely from a previous layer of gas ejected from the star in a similar bipolar manner.   JD 

 

The following photo by Mario Motta from Massachusetts using a 32-inch reflector. 

NGC2371

 

Inverted pencil sketch by Mike McCabe from Massachusetts.

100_7635G

 

Inverted pencil sketch by Jaakko Saloranta from Finland using an 8-inch reflector.

NGC2371

 

Using a 76 mm (3-inch) Reflector and a Relaxing Hour….Enjoying The Wonders of The Night Sky

March 17, 2018

Last night, I didn’t want to set up a larger telescope, but instead scanned the sky for more than an hour using a small 76 mm reflector.  

No notes, no sketches….just relaxing, and taking the advice of Leslie Peltier:  

“Were I to write out one prescription designed to alleviate at least some of the self-made miseries of mankind, it would read like this:  “One gentle dose of starlight to be taken each clear night just before retiring”.  Leslie Peltier

“Many books explain how to observe the sky; Starlight Nights explains why.”  In a way, Leslie Peltier is the patron saint of One Minute Astronomer.”   David Levy

So the next time you want to observe, but are a bit too tired, the weather is too cold or too hot:  why not spend a few minutes with binoculars, or a very small telescope, and you just might be surprised at what you see. Then there is also the benefit of a great nights sleep.  

I enjoy amateur astronomy much more than I did 50 years ago…as a 13 year old kid trying to find my way as an amateur in a weedy field, in the foothills of North Carolina.  

Roger Ivester

IMG_0081

M41- Open Cluster in Canis Major-February 2018 Observer’s Challenge Report #108

March 9, 2018

FEBRUARY 2018 OBSERVERS CHALLENGE – M-041

Pencil sketch:  6-inch reflector @ 46x and 1.3º field of view: 

M41 Adjusted

Inverted colors

Rogers M-041 Inverted

Messier 41 (NGC 2287) at magnitude 4.5 is visible without optical aid. I often enjoy viewing this cluster with a pair of 7 x 21 mini-binoculars. It is easily located at about 4º south of Sirius, and NW of 6.0 magnitude 12 Canis Majoris.

A beautiful, but sparse cluster, very irregular shape, with several small chains of stars. The most noticeable star chains are on the SW and NE.

When using a 6-inch reflector, I can count ~60-70 stars. A small circlet of stars envelope the central region of the cluster. M41 contains the famous red star, known as the Espin star (HD 49091) magnitude of 6.9 and a K3 spectrum. The star was named after Rev. T.E. Espin (1858-1934.) I normally see this star as a deep-orange in color.    Roger Ivester

 

M41 image by James Dire:  

102mm (4-inch) f/7.9 refractor using a 0.8X focal reducer field flattener with an SBIG ST-2000XCM CCD camera. The exposure was 30 minutes. North is up, and east to the left.

M41

M41 is a beautiful galactic star cluster located 4° south of the bright star Sirius. The cluster can be seen naked eye from a dark site. It’s mag. 4.5 and is 39 arcminutes in diameter. It lies 2,350 light-years away

Aristotle noted M41 in 325BC as being a cloudy patch in the sky. The cluster was first cataloged by the Italian astronomer Giovanni Batista Hodierna in 1654, and then John Flamsteed in 1702. Charles Messier added it to his catalog in 1765.

M41 has about 100 stars. The brightest is a mag. 6.9 red giant star near the apparent center of the cluster, cataloged as HD49091. This K3 star has the brightness of 700 suns. The cluster is estimated to be 190 to 240 million years old and has a chemical composition similar to the sun.

The brightest star in the image is near the bottom edge, left of center. That star is 12 Canis Majoris, or HK Canis Majoris. HK is a mag. 6 blue giant star with a surface temperature of 18,000K. HK is only half the distance of M41 and thus is not a member of the cluster. The next brightest star in the image is the red giant HD49091, the red giant star near the center of the cluster.   James Dire