Archive for the ‘Work File Only – Observer’s Challenge Reports’ category

IC 1805 – “Cluster + Nebula” In Cassiopeia – December 2019 – Observer’s Challenge Report #131

November 23, 2019




Report #131

IC 1805 Open Cluster in Cassiopeia

Observer’s Challenge Report Final:  Click on the following link



Note:  The following are mostly original notes, with very little if any editing, to preserve the feelings and thoughts of the observer during the observation.  This is not the “official” Observer’s Challenge report, but what I call a “work-file” just to organize the entries.  Roger Ivester

     IC 1805 is a 6.5-magnitude cluster about 62 stars that spans about 20 arcminutes. It’s nearly centered on the group’s brightest member, HIP 11832 shining at magnitude 7.1. The cluster is young at only 2.5-million years and we see it at a distance of roughly 6,500 light-years. IC 1805 is enveloped in and associated with the emission nebula Sharpless 2-190, commonly called the Heart Nebula, which sprawls across 1.6 º of sky.

     Edward Emerson Barnard discovered IC 1805 photographically and included it on the first two plates of his wonderful Photographic Atlas of Selected Regions of the Milky Way.  The atlas can be viewed online at:     Intro by Sue French  


IC 1805, December 2019, Observing Report by Mario Motta: 

Color Image:  This was combined with 1 hour each of Oxygen 2 filter and Sulfur filter:  See attached.

IC 1805 (the Heart Nebula), North is to the right on this image, rotated to show the “heart” shape more readily.

Of course…to a cardiologist the Right heart (on the left, person facing you), is very “enlarged” so this is a rather sick heart, with what I would call right heart failure.    Mario Motta 





Sue French: Observer from New York:

14×70 binoculars:

IC 1805 is a fairly large, loose open cluster of six to eight moderately bright stars, depending on the borders, plus about 15 more stars on the backdrop.

105/610mm (4.1-inch f/5.8) refractor

     17×: Nebulosity is faintly visible without a filter, a little better with a UHC filter, and very nice with an O III filter. The brightest areas include: the IC 1805 cluster; a wide arc that runs between clusters IC 1805 and NGC 1027 and then loops around north of the IC 1805 cluster; and a small patch in the position of the nebula complex NGC 896/IC 1795. A fainter arc starts between the two clusters, loops around south of cluster IC 1805 and then northward on the western side of this cluster.  Both loops are quite patchy with very uneven brightness. Nebulosity also stretches from cluster IC 1805 to the eastern loop.

     87×: About 40 stars are visible in cluster IC 1805. Its brightest member is a double star, residing in a rough circlet of fainter suns at the cluster’s heart. Arms of stars starting north and south of the circlet curve westward. Two fairly bright stars northeast form a faint star with the lucida.  A broad scattering of stars straggle east through southeast from the circlet, while extremely faint specks of light can be seen within the circlet and rounding out the group.

     The double star is Stein 368 AB (STI 368 AB), PA 97º, separation 9.9″, component magnitudes 8.0 and 10.1. NGC 1027 displays about 50 stars centered on the group’s central lucida. Starting north-northwest of the star, its brightest attendants spiral outward from it for about 1½ turns.

     These observations were made in the northern Adirondack Mountains of New York, where my naked-eye limiting magnitude near Polaris was 6.3.


Roger Ivester:  Observer From North Carolina 

     In November I used a 6-inch f/6 reflector in an attempt to see the nebula in IC 1805. My eyepiece of choice for this night was a 2-inch-barrel 26mm with an O III filter. This gave me a field of view of 2º. 

     Scanning the area before using the O III filter, I first saw open cluster NGC 1027. A bright cluster at magnitude 6.7, consisting of about 20 stars with one brighter member located in the center. This cluster is located just to the east of IC 1805. 

     Now to IC 1805: I could easily see the cluster of stars located in the central region of the IC 1805 nebula. When adding an O III filter, I scanned the area for more than an hour; however, I cannot say definitively that I could see any nebulosity.

     On December 15, 2019, I used an 80mm f/5 refractor, with a 24mm eyepiece and a UHC filter. I was a bit dubious before beginning my observation that I’d be able to see the IC 1805 nebula based on my results using a 6-inch reflector only a month earlier, and with similar sky conditions. 

     After about thirty minutes, I could not see any of the nebula, but the central stars were easy and bright. However, when I began using my “manual” slow-motion controls, I began scanning across the IC 1805 area, and to my surprise, I began seeing very faint brightenings in the area. I scanned one section at a time, and was able to sketch extremely faint tentacles and fingers of nebulosity, only marginally brighter than the background. After more than two hours of “slow-motion” scans, well over two hundred crossings, I was able to sketch some of the brighter sections, encircling the central cluster. 

Telescope: 80mm f/5 achromatic refractor 

Eyepiece: 24mm + UHC filter 

Sketch Magnification: 17× 

Field of View: ~3.5º 

Roger IC 1805


James Dire:  Observer From Illinois 

     The Heart Nebula, IC 1805, is part of a vast complex of nebulae located in the constellation Cassiopeia. The nebula is located five degrees southeast of the star Segin and eight degrees east of the star Ruchbah. Segin and Ruchbah are the two easternmost stars making up Cassiopeia’s “W” asterism. 

     The brightest part of the Heart Nebula is separately known as NGC 896. NGC 896 was discovered by William Herschel in 1787 using his 18.7-inch reflector. NGC 896 measures 27 x 13 arcminutes and is estimated to be magnitude 10.

     The Heart Nebula itself extends about one degree in both right ascension and declination. The Heart Nebula lies 7500 light years away in the Perseus arm of the Milky Way Galaxy.

     IC 1805 is also the designation of an open star cluster in the middle of the Heart Nebula. This cluster is also known as Melotte 15. This loose open cluster is estimated to be a mere 1.5 million years old and contains several bright stars 50 times the Sun’s mass. These stars are responsible for exciting the hydrogen gas in the Heart Nebula resulting in the red glow as seen in photographs.

     My image of IC 1805 was taken with a 71 mm f/4.9 apochromatic refractor using an SBIG STF-8300C CCD Camera. The exposure was 140 minutes. In the image north is up and east to the left.

     The second image has labels pointing out the location of NGC 896 and the central star cluster in IC 1805. Two more open clusters are labeled in the image. The first is NGC 1027 located on the east side of the heart. NGC 1027 is a bright rich cluster of approximately 50 stars all within a 20 arcminute circle. The cluster has a total magnitude of 6.7. The other cluster is called Markarian 6 and is located southwest of the heart. Markarian 6 is magnitude 7.1 and is 6 arcminutes in diameter. All three star clusters contained in the nebula are worthy of inspection with any telescope at medium to high powers.

     My best view of the Heart Nebula was with my 14-inch f/6 Dob using a 26mm eyepiece (82x). This combination provides a one-degree true field of view. While the view comes nowhere close to my image, it was possible to see many of the brighter regions of the nebula, especially NGC 896 and the three above-mentioned star clusters.    




NGC 246 – Planetary Nebula – Cetus November 2019, Observer’s Challenge Object

November 22, 2019




NGC 7448 – Galaxy in Pegasus – Observer’s Challenge Object – October 2019

November 9, 2019

The complete Observer’s Challenge report link as following: 


My first observation of galaxy NGC 7448, came on the night of October 24, 1994, using a 10-inch reflector.   Roger Ivester 

October 24th 1994: 

“10-inch @ 57x, can vaguely detect with direct vision, situated between two two dim stars, which are oriented ESE-NW of the galaxy.  When increasing the magnification to 190x, the galaxy appeared elongated, still fairly difficult, but could be seen with direct vision.  However, averted vision allowed a clear view of the elongated shape, oriented N-S, with a brighter stellar core.” 

It would be almost twenty five years before I would observe this galaxy again, on September 26th, 2019.  

An astronomy friend, Richard Nugent from Massachusetts, visited both my wife Debbie and I, and were fortunate to be able to observe the galaxy that night.  We estimated the NELM at about 5.0, which is actually pretty good for my back yard this time of the year in the foothills of North Carolina. 

Using a 10-inch reflector, the galaxy was fairly easy to see with direct vision, at 114x.  When increasing the magnification to 174x, using a 12.5 mm eyepiece and a 1.9x Barlow, the galaxy appeared elongated and oriented N-S, with a brighter core.   

However, for a faint galaxy such as this, and using a 10-inch reflector in a moderate-plus light polluted location….just being able to recognize and see a few minor details can be an accomplishment or considered a success.  

I was pleased to be able to see the very faint double star, magnitudes, 13.5 and 14.0 located to the NNW of the galaxy.   (Magnitudes from NOMAD, and provided by special advisor to the Observer’s Challenge, Sue French)  

The double is actually a triple, but the third component is very faint at magnitude 15.7, which is far too faint for my 10-inch reflector.  I’m hoping that others using much larger telescopes were able to see this third star.  

Roger Ivester 

Pencil sketch:  10-inch reflector @ 174x 

Rogers NGC-7448 Inverted

Notes and pencil sketch by Sue French:

NGC 7448 is the brightest of five NGC galaxies that mark the corners of a nearly equilateral triangle with 28′-long sides. It sits at the triangle’s western corner. I first logged NGC 7448 in 1988 for the Astronomical League’s Herschel 400 observing program. Since then I’ve visited it a number of times, along with its buddies, through a few different scopes. My Observer’s Challenge sketch was done with my 254/1494mm (10-inch f/5.8) reflector at magnifications of 187× to 299×.

NGC 7448 appears fairly bright and elongated at 68×, with a 10th-magnitude star in attendance 2½′ east by south of the galaxy. At 115× NGC 7448 presents a moderate-size oval glow, twice as long as wide, that grows gently brighter toward the center. At 187× the galaxy shows a south-by-east tilt. Its large, elongated core looks brighter in the north. At 213× I estimate a size of about 1.7′ × 0.8′.

NGC 7465 shares the field of view with NGC 7448 at 68×, but it’s dimmer and roundish with a tiny, bright center. The galaxy sits 4′ east of an 8th-magnitude star and is tucked inside the western corner of a ¼° trapezoid formed by that star and three others, magnitudes 9 and 7. At 115× the small glow of the galaxy is easily viewed. Its core is tipped NNW and harbors a tiny bright nucleus. At magnifications of 187× to 299×, the core grows brighter toward a stellar nucleus and the faint halo is just a thin coating of fluff that slightly rounds out the galaxy’s profile.

NGC 7463 emerges as an east-west glow at 115×, dwelling just 2½′ WNW of NGC 7465. At 213× it shyly offers an elusive stellar nucleus and has a very elongated façade. At 299× NGC 7463 maintains an almost uniform surface brightness.

NGC 7464 is a tiny little thing dangling south of the eastern half of NGC 7563. I was only able to spot it during one of my observing sessions. With averted vision at 299×, I could catch repeated glimpses of the galaxy as a round dot. It was difficult to see, and I couldn’t hold it steadily in view.

Together NGC 7463, NGC 7464, and NGC 7465 hold down the western corner of the galaxy-pinned triangle. 

NGC 7454 is parked on the triangle’s northern point and is visible even at 43× as a tiny smudge off the ESE side of a 11½-magnitude star. A 9th-magnitude star lies 4½′ east by north. The galaxy is faint and somewhat oval at 68×, and 115× reveals a relatively large, bright, oval core. In addition to the 11½-magnitude star near the galaxy’s WNW side, the higher power captures a 13½′-magnitude star a little farther away to the NNW. NGC 7454 grows gently brighter toward the center at 187×, and at 213× I estimate the visible size as about 1′ × ⅔′.

I’d hoped all the galaxies would fit in my 187×, 32′ field of view, but that wasn’t big enough, so I cheated and nudged the scope north to get NGC 7454. I also used higher magnifications to add some of the details. Sketching stars, I began with those near the galaxies and brighter field stars. For three nights it kept clouded up before I could try to get the rest, so I decided leave the sketch as is. North is to the left and west is up. 

NGC 7488 group c inv

Mario Motta image:  32-inch telescope

See attached, 90 mins exposure on NGC 7448. Wiki says it is 80 million LY away, about 60,000 LY across. Notable for “detached spiral arm segments” which I think you can easily see in my image. Interesting object.

Taken with 32 inch scope SBIG STL 1001E camera, 500 seconds subs, 90 mins total exposure.  Processed in pixinsight. 


M71 – Globular Cluster In Sagitta – Observer’s Challenge Object – September 2019

October 15, 2019


6-inch reflector:  Pencil sketch, using a blank 5 x 8 notecard, with the colors inverted.  Roger Ivester

Rogers M-071 Inverted



M11 – Open Cluster in Scutum – Observer’s Challenge Object – August 2019

August 22, 2019

Complete report: AUGUST 2019 OBSERVERS CHALLENGE – M-011-1

The following pencil sketch, with the colors inverted was made using a 6-inch f/6 Newtonian reflector telescope @ 83x.  

Rogers M-011 Inverted

Image by Mario Motta: 32-inch telescope 


Image by Michael Brown using a Canon digital SLR camera, through an 8-inch Celestron SCT.  This photo is from 12 30-second exposures (6 minutes total) at ISO 3200.


The following image was taken with a 10-inch f/6.9 Newtonian with the same camera. The exposure was 30 minutes. Most of the stars in the image belong to the cluster, perhaps 500-1000 visible here. The faintest stars in the image are magnitude 16!    James Dire


Stock Canon 80D, 400mm f/2.8 lens, ISO 800, 35subs x 30sec = 17.5 min total
exposure, 1/2 scale (4 arcsec/pixel).  No filters.  By Doug Paul 




NGC 5377 – Galaxy – Canes Venatici – June 2019 Observer’s Challenge Object

July 3, 2019

Observer’s Challenge Report:


Pencil sketch:  10-inch reflector @ 160x 

Image by Mario Motta – 32-inch reflector 


NGC 6482 – Galaxy in Hercules – July 2019 Observer’s Challenge Object

April 30, 2019

Observer’s Challenge Report:  JULY 2019 OBSERVERS CHALLENGE – NGC-6482

In an attempt to observe the July Observer’s Challenge object, galaxy NGC 6482, a bit early to avoid the heat and high humidity of June and most of the summer months, here in the foothills of North Carolina:  

Telescope: 10-inch f/4.5 reflector.  I went out last night at about 2:00 AM (May 30th) only to find a not so transparent sky, with a NELM of about 4.6, temperature 55º and with 99% humidity.  The high moisture mixed with high-pollen created a bright sky for sure!

However, while outside, I thought I’d make the best of it and give the galaxy a try.  At 2:00 AM the object was still too low in the east, but I wanted to find the “spot” and work on the object.  At about 3:30 it was high enough to get serious.  

At 5:00 AM, I called it quits, as the sky was beginning to brighten.  This might be a difficult object from my backyard with a 10-inch reflector.

On a better night in June.  Pencil sketch with the colors inverted.  Roger Ivester

Rogers NGC-6482 Inverted 

NGC 6482

The following Notes and image by Mario Motta from Massachusetts, 32-inch telescope:

NGC6482, is a small lenticular galaxy.

I can see why the visual observer would have difficulty….due to having a star just off center of the galaxy center, and just as bright!   So…the slightly fainter outer galaxy would be hard to see by the contrast, a bit of sort or similar to the blinking planetary. 

I had to do some special processing to enhance the star, and slightly de-enhance the galaxy so both can be seen.  Mario Motta 


NGC 6482:  Observation Notes and Sketch by Sue French:

I  took a look at NGC 6482 on Friday, May 24 at 12am EDT with my 254/1494mm (10-inch f/5.8) Newtonian.  The seeing was below average, and the transparency was fair.

At 43× NGC 6482 is just a little fuzzball.  It dangles beneath (south of) the base of a slender, 6.3′-tall trapezoid made by four 11th-magnitude stars.  At 115× the galaxy presents an oval glow tipped northeast by east and sports a superimposed star near the galaxy’s center. 

The sketch was made at 187×, at which this petite galaxy wears a fainter fringe and appears roughly 0.7′ long.  The galaxy showed no core, and I’ll be interested in finding out whether anybody else spotted one. 

Perhaps the proximity of the superimposed star hid the core, or maybe one would show if viewed higher in the sky.  It was about 52° above the horizon when I observed it.   Sue French 

NGC 6482 inv.jpg


NGC 2964/2968/2970 – Galaxies in Leo – April 2019 Observer’s Challenge Objects

March 28, 2019

Observer’s Challenge Report:


Pencil sketch with colors inverted:

Rogers NGC-2964 Invereted

NGC 2964-68-70

Image by Mario Motta from Massachusetts, 32-inch telescope:



NGC 2300 and NGC 2276 – Galaxy Pair in Cepheus – March 2019 Observer’s Challenge Objects

March 7, 2019

March Observer’s Challenge Complete Report:  Click on the following link:



Pencil sketch 10-inch reflector @ 183x: 

NGC 2300 and 2276

Inverted color pencil sketch:  

Rogers NGC-2300 Inverted

NGC 2300 and NGC 2276 – Galaxies in Cepheus –  Date:  Wednesday, March 6th 2019 Telescope:  10-inch f/4.5 reflector – Sketch magnification:  183x – Eyepiece:  12.5 mm + 2x Barlow – FOV:  0.33º – 20 arc minutes – Conditions:  NELM ~5.0-5.2 

NGC 2300:  Bright, high surface brightness, brighter very concentrated nucleus, mostly round, but with a very subtle E-W elongation.  

NGC 2276:  Extremely difficult, mostly round, very low surface brightness, appearing only as a brightening in the sky.  Very even without concentration.  The glare from a magnitude 8.5 star located two arc minutes WSW of the galaxy, hinders the view.  Averted vision required.  The eyepiece view of this galaxy was far more illusive than my pencil sketch projection.  Roger Ivester 


Image and information by Mario Motta – 32-inch f/6 telescope 


I fought some clouds late, and had to drop some subs, but got about 65 minutes total for this image.  

SBIG STL 1001B camera, five minute subs to keep the bright mag. 8.5 star, only a couple arc minutes away from blooming too much, with the 32-inch f/6 telescope, and then processed in PixInsight.  

NGC 2300 is mostly featureless as an elliptical, but I find NGC 2276 very interesting.  It has sharp arms that are chock full of H alpha knots it would appear.  

I wonder if NGC 2276 is a starburst galaxy?  Possibly by a close approach to 2300?  Such an interesting galaxy and image.  

Mario Motta from Massachusetts  

Supplemental Post: 

I  did a search and was right, concerning NGC 2276!  It is a starburst galaxy, see below:  A short abstract from Chandra observations.  Mario  


The starbusting, nearby (D = 32.9 Mpc) spiral (Sc) galaxy NGC 2276 belongs to the sparse group dominated by the elliptical galaxy NGC 2300. NGC 2276 is a remarkable galaxy, as it displays a disturbed morphology at many wavelengths. This is possibly due to gravitational interaction with the central elliptical galaxy of the group. Previous ROSAT and XMM–Newton observations resulted in the detection of extended hot gas emission and of a single very bright (∼1041 erg s−1) ultraluminous X-ray source (ULX) candidate. Here, we report on a study of the X-ray sources of NGC 2276 based on Chandra data taken in 2004. Chandra was able to resolve 16 sources, 8 of which are ULXs, and to reveal that the previous ULX candidate is actually composed of a few distinct objects. We construct the luminosity function of NGC 2276, which can be interpreted as dominated by high-mass X-ray binaries, and estimate the star formation rate (SFR) to be ∼5–15 M yr−1, consistent with the values derived from optical and infrared observations. By means of numerical simulations, we show that both ram pressure and viscous transfer effects are necessary to produce the distorted morphology and the high SFR observed in NGC 2276, while tidal interaction have a marginal effect.

NGC 2175: Reflection Nebula in Orion – February 2019 Observer’s Challenge Object #120

January 7, 2019

Observer’s Challenge Report:  FEBRUARY 2019 OBSERVERS CHALLENGE – NGC-2175

If you have identification questions concerning reflection nebula NGC 2175, the following information by Sue French will be of value during your observation.   

NGC 2174 is a brighter knot in the northern part of NGC 2175.  The existence of a true cluster within NGC 2175 is dubious, but the visually involved stars are nonetheless known as Collinder 84.   Sue French


Hi Roger, learning curve to do mosaic well in Pixinsight, but here is my effort.

This is a composite of east and western end of the monkey.
This one only includes Ha and O3 data, S2 could not be incorporated in the composite due to eastern end getting clouds at that time.  So…came out OK, I think.
The following image is about 5 -6 hours total sub time to get. Strl 1001E camera (field of view 17×17 arc minutes per sub) the combo spans about 30 arc minutes. Taken with my 32 inch f/6, 4800mm FL, several nights work


Pencil Sketch by Roger Ivester

ngc 2175

Pencil sketch with colors inverted:

rogers ngc-2175 inverted

Date: January 9, 2019; Conditions: Excellent; NELM 5.2 

Telescope: 10-inch f/4.5 Newtonian reflector; Elapsed time for this object:  Three hours;  Sketch Magnification: 57x; Filter:  O III; Field of View: 1.1º – 66 arcminutes;  Addition magnification, without filter: 95x 

At 57x, using a 20 mm eyepiece, plus O III, the nebula was very easy to locate and see, however, almost invisible without the filter.  The nebula is brightest and more concentrated around the central mag. 7.5 star.  Dark lanes are abundant throughout the nebula, especially looping around the south edge.  With averted vision, NGC 2174, a nebulous patch could be observed on the NW corner, however, not constant.  A small cluster of stars to the ENE of NGC 2175, has the appearance of having nebulosity.  When removing the O III filter, and increasing the magnification to 95x, and with averted vision, many faint stars began to appear within the nebula as shown in my sketch.  Roger Ivester   


Image provided by David Blanchette from Las Vegas:  North is up and west to the right.  Telescope and equipment:  8-inch Explore Scientific Newtonian Astrograph, Canon Rebel T7i, 50x60s, ISO 6400, Baader UHC-S filter, Deep-Sky Stacker. 

ngc 2174 north crop


Observation notes by Sue French:

I hope to sketch this for the Observer’s Challenge, but in the meantime here are my past logs for NGC 2175:


3-1-91, 9:00 PM EST, 10-inch/f6 homemade Newtonian, 32mm Plössl+ O III filter, Seeing: fair, Transparency: good, Aurora

Large, faint, mottled nebula containing a 7.6-magnitude star in a rich field of fainter stars.  About one-half degree in diameter.


2-12-96, Winter Star Party, 11:00 PM EST, 105mm AP Traveler prototype, 13mm Nagler, Seeing: fair, Transparency: good

Very nice nebula about 20 arcminutes in diameter. Obvious without filter, but better with the PTR Optics narrowband filter and even better with an O III filter. 7.6-magnitude star near center plus about a dozen faint stars superimposed. Slight mottling to nebula with hints of some dark lanes.


3-1-96, 9:35 PM EST, 10-inch/f6 homemade Newtonian, 35mm Panoptic, O III filter, Seeing: fair, Transparency: good

A large, round glow through the O III filter, about 23 arcminutes across.  Despite the outlines in Uranometria, the nebula looks pretty much centered on the 7.6-magnitude star embedded within. The nebula brightens gradually toward the center.  The view is similar with a UHC filter, but not quite as contrasty. Without a filter, the nebula is subtle. It has a dusting of faint stars across it.


12-23-16, 12:40 AM EST, My great-nephew’s 8-inch Orion Intelliscope in North Carolina

Visible in 9×50 finder with a 7.6-magnitude star embedded near center.

22mm Nagler: Large, easy to see.  The star near the center is in a star chain that has a prominent hump to the east.  Subtle dark nebulae thread the glow.  Many superimposed stars. The nebula shows nicely when adding a UHC filter.  Somewhat irregular in shape.  The Sh2-252 E nebulous knot doesn’t show particularly well, but it has a superimposed star near its center, too. O III filter makes the nebula seem quite bright to a diameter of 22 arcminutes.

9mm Nagler: The unrelated cluster Pismis 27 (sometimes called NGC 2175.1) shows 6 fairly bright stars in a SSE-NNW bunch, plus a half-dozen faint stars.  Overall the group spans about 4.2 arcminutes.


1-30-17, 8:40 PM EST, 10-inch/f5.8 homemade Newtonian, Seeing and Transparency; fair, snowcover, 14°F. breezy

2175 is visible through the 9×50 finder as a distinct sizable glow around a star.

22mm Nagler: The nebula is subtle. Pismis 27 shows 9 stars.  Adding a UHC filter shows a beautiful, large nebula threaded with dark lanes.  The northern border is particularly irregular.  The nebulosity covers about  25 arcminutes.  There’s a very small, brighter patch (Sh2-252 E) 3.2 arcminutes ENE of the star.  The bright patch contains a star and has a pair of matched (m = 10.6, 10.7) stars 2.1 arcminutes north.  There may be a touch of nebulosity in Pismis 27.

22mm Nagler + O III filter: Also makes the nebula stand out well, but I prefer the UHC, which shows off the lines and chains of stars meandering across the nebula.

13mm Nagler: Pismis 27 shows 15 stars in about 4½ × 3 arcminute group running approximately north-south. Includes the close double J1922.


My first mention of NGC 2175 in my S&T column, which was then called Small-Scope Sampler, in the February 2004 issue:

Another nice nebula, NGC 2175, sits 1.4º east-northeast of Chi2 (c2) Orionis.  In my little refractor at 47x, I find the nebula obvious without a filter.  However, a narrowband filter betters the view and an OIII filter helps even more.  An 8th-magnitude star is visible near the center, and a dozen faint stars are superimposed.  The nebula is slightly mottled and shows hints of dark lanes.


NGC 2175 is sometimes plotted as an open cluster in star atlases while the designation NGC 2174 is given to the nebula.  Neither is correct.  NGC 2175 was discovered sometime in the mid-1800s by the German astronomer Carl Christian Bruhns and first reported by Arthur Auwers who described it as an 8th-magnitude star within a large nebula.


NGC 2174 is actually a bright knot of nebulosity in the northern edge of NGC 2175.  It was discovered at Marseille Observatory by Édouard Stephan, widely recognized for the group of galaxies that bears his name – Stephan’s Quintet.  Folks with larger scopes might like to hunt for NGC 2174 and for the even brighter knot Sh 2-252 E, respectively located 11′ north-northwest and 3.3′ east-northeast of the 8th-magnitude star.


The existence of an open cluster within the nebula seems debatable.  It was the Swedish astronomer Per Collinder who first noted a cluster here and mistakenly equated it with NGC 2175.  The cluster’s proper designation should then be Collinder 84, but there doesn’t appear to be an obvious concentration of stars within the nebula.  Collinder 84 is supposed to consist of the clumps of stars loosely scattered across most of NGC 2175.  Does it look like a cluster to you?

Sue French