RolandosCY
June 15th, 2016, 09:55 PM
The Extragalactic Flotilla of M92
Sixteen galaxies located within a one degree circle centered at RA 17h 15m, Dec + 43 23'
This week’s Object of the Week is a multi-target treat, next to a much bigger wonderful deep sky object: A group of at least sixteen galaxies, all floating within one degree to the north and west of the grand globular cluster M92 (an object itself worthy of being an OOTW!).
I first read about the galaxies around M92 in an old S&T article by Ken Hewitt-White, at a time when as a buddying deep sky observer I was just dreaming of locating such objects. The years passed, and in 2015 I decided to tackle myself the challenge of the M92 galaxies. Except I had a problem: I misplaced my old magazine and I could no longer find my original reference. So, last year I postponed my search, but this year I decided to tackle the area, even without the article.
Using Megastar, I immediately discovered a string of NGC galaxies in a 30 arc-minute E-W line north and west of M92. Not knowing what to expect, I slew my 18” dob to the area. Well, none of the galaxies was a real eye-catcher, but all five could be readily seen, especially at high power. NGC 6336, the easternmost galaxy, was a faint 14th magnitude diffuse oval with a very slightly brighter center, while NGC 6332 was easier to see, being brighter at magnitude 13.8 and apparently of a higher surface brightness. NGC 6329 is the middle galaxy in the string, and at 12.9 is the brightest. Indeed, it was a touch easier to see than the others, appearing as a faint oval with a brighter center. NGC 6327, tucked on one side of a faint triangle of stars (of which one is a double) is listed as magnitude 15th. Yet, it was almost as easy as NGC 6329 as it is a very small round patch of light, barely 20 arc seconds across – thus with a high surface brightness. The westernmost of the NGC galaxies is 6323, another faint oval at magnitude 14.2. All these galaxies (except NGC 6327)had oval shapes of about 1.2 x0.6 arc minutes, so they were not large, and high power was best for really revealing their shape.
I could remember that several more galaxies were mentioned in the article, but I had no idea which, so decided to tackle them separately the following evening. Again with Megastar, I produced new charts that now included several CGCG galaxies, plus IC 4645 (all that could fit along with the NGC galaxies and M92 in a one-degree field). I was not really positive about the outcome, yet I was able to ferret out all the galaxies I charted, namely IC 4645, CGCG225-91, 225-84, 225-87, 225-70, 225-81, 225-83, and -225-79. All of these galaxies were faint (or extremely faint!) and tiny, and were identified after careful scrutiny, appearing for the most part as slightly fuzzy very faint stars. All have magnitudes between 15.2 and 15.8. CGCG 225-91 was the most difficult, being visible only at times with direct vision. With care, I could see M92 and most of these galaxies in my 13mm Ethos 40’ field of view. The whole view did remind me of a big naval ship such as an aircraft carrier, being accompanied with a flotilla of lesser vessels. M92 was the big ship, and the tiny galaxies the flotilla, hence my title.
2143214421452146
On the next evening I set up my 6” achro, and tried to see if I could spot any of the galaxies, expecting a negative result. To my surprise, using my Nagler 7mm giving me 129X I was able to detect NGC 6332 and NGC 6329. They were really tough, a borderline observation, but I was able to hold them steady enough to draw the, I could not spot any of the other galaxies though.
2147
I tried to locate observations of these galaxies by others, but except for Steve Gottlieb’s observations of the NGC galaxies on the NGC/IC project homepage, http://www.ngcicproject.org/ (using 17.5” and 18” telescopes) I could not find any observations. Steve’s observations were quite similar to mine. Yet, having seen NGC 6332 and 6329 in a 6” achro, I believe that under good conditions a 12” could possibly show at least all the NGCs and even the brightest CGCG galaxies.
Normally, this would have been the end of the article, but as luck would have it, on the very next morning after my 6” observations I accidentally discovered a misplaced stack of old S&T magazines, including the July 2001 issue which contained the article that inspired this week’s Object of the Week. Needless to say, I immediately checked the article to compare my observations with those of Ken Hewitt-White. Well, for the most part we have had similar observations. I did observe a couple of CGCG galaxies that went unobserved by Hewitt-White, yet he did observe some “anonymous” galaxies that were not plotted by Megastar but were visible in the Deep Sky Survey images of the area. I did prepare charts based on the DSS images to track down these anonymous galaxies myself, but work commitments and the appearance of the moon did not allow me to observe them, a project for the next new moon period. In his article, Ken Hewitt-White mentions that under very dark skies he did manage to observe all the NGC galaxies and some of the CGCG ones with his 10-inch dob, confirming what I suspected after observing this area with a 6-inch refractor.
Here is a list of all galaxies mentioned by me in the article above, plus those mentioned by Ken Hewitt-White in his article. I have prepared a DSS image with all sixteen galaxied mentioned. Note that in the S&T article, the CGCG galaxies are labeled under the PGC catalog. In the list both identities are mentioned, as well as the A1-A8 labeling used in the S&T article. To avoid cluttering, on the DSS image I have numbered them from 1 to 16 as listed below.
1 – NGC 6336
2 – NGC 6332
3 – NGC 6329
4 – NGC 6327
5 – NGC 6323
6 - CGCG 225-91 = PGC 59984 = A1
7 – CGCG 225-84 = PGC 59930 = A2
8 – IC 4645 = A3
9 – CGCG 225-87 = PGC 59950 = A6
10 – CGCG 225-70 = PGC 59859 = A8 (note that in the S&T article labeled as PGC 91583)
11 – CGCG 225-81 = PGC 59914 (not in S&T article)
12 – CGCG 225-83 = PGC 59931 (not in S&T article)
13 – CGCG 225-79 = PGC 59912 (not in S&T article), not visible in the DSS image (just off the southern edge of the image).
14 – A4 in S&T article, not observed by me
15 – A5 in S&T article, not observed by me
17 – A7 in S&T article, not observed by me (note that by mistake I labeled it “17” instead of 16, that’s why 16 is missing!)
2148
So, this Object of the Week is more reminescent of a treasure hunt than of a very detailed study of a single object. It certainly gave me lots of pleasure in trying to hunt down these faint fuzzies, and I hope it gives the same pleasure to many others. Although it is most suited for those with medium to large scopes, users of smaller scopes should also attempt it, and should remember that even if they don't manage to locate the galaxies, there is a superb consolidation prize in observing the beautiful M92. And I should express many thanks to Ken Hewitt-White for without his superb article I doubt I would have ever considered searching for faint galaxies around M92!
So, next time you are out, think Hercules and his labors, try this labor for youself, and ...
GIVE IT A GO AND LET US KNOW!
Sixteen galaxies located within a one degree circle centered at RA 17h 15m, Dec + 43 23'
This week’s Object of the Week is a multi-target treat, next to a much bigger wonderful deep sky object: A group of at least sixteen galaxies, all floating within one degree to the north and west of the grand globular cluster M92 (an object itself worthy of being an OOTW!).
I first read about the galaxies around M92 in an old S&T article by Ken Hewitt-White, at a time when as a buddying deep sky observer I was just dreaming of locating such objects. The years passed, and in 2015 I decided to tackle myself the challenge of the M92 galaxies. Except I had a problem: I misplaced my old magazine and I could no longer find my original reference. So, last year I postponed my search, but this year I decided to tackle the area, even without the article.
Using Megastar, I immediately discovered a string of NGC galaxies in a 30 arc-minute E-W line north and west of M92. Not knowing what to expect, I slew my 18” dob to the area. Well, none of the galaxies was a real eye-catcher, but all five could be readily seen, especially at high power. NGC 6336, the easternmost galaxy, was a faint 14th magnitude diffuse oval with a very slightly brighter center, while NGC 6332 was easier to see, being brighter at magnitude 13.8 and apparently of a higher surface brightness. NGC 6329 is the middle galaxy in the string, and at 12.9 is the brightest. Indeed, it was a touch easier to see than the others, appearing as a faint oval with a brighter center. NGC 6327, tucked on one side of a faint triangle of stars (of which one is a double) is listed as magnitude 15th. Yet, it was almost as easy as NGC 6329 as it is a very small round patch of light, barely 20 arc seconds across – thus with a high surface brightness. The westernmost of the NGC galaxies is 6323, another faint oval at magnitude 14.2. All these galaxies (except NGC 6327)had oval shapes of about 1.2 x0.6 arc minutes, so they were not large, and high power was best for really revealing their shape.
I could remember that several more galaxies were mentioned in the article, but I had no idea which, so decided to tackle them separately the following evening. Again with Megastar, I produced new charts that now included several CGCG galaxies, plus IC 4645 (all that could fit along with the NGC galaxies and M92 in a one-degree field). I was not really positive about the outcome, yet I was able to ferret out all the galaxies I charted, namely IC 4645, CGCG225-91, 225-84, 225-87, 225-70, 225-81, 225-83, and -225-79. All of these galaxies were faint (or extremely faint!) and tiny, and were identified after careful scrutiny, appearing for the most part as slightly fuzzy very faint stars. All have magnitudes between 15.2 and 15.8. CGCG 225-91 was the most difficult, being visible only at times with direct vision. With care, I could see M92 and most of these galaxies in my 13mm Ethos 40’ field of view. The whole view did remind me of a big naval ship such as an aircraft carrier, being accompanied with a flotilla of lesser vessels. M92 was the big ship, and the tiny galaxies the flotilla, hence my title.
2143214421452146
On the next evening I set up my 6” achro, and tried to see if I could spot any of the galaxies, expecting a negative result. To my surprise, using my Nagler 7mm giving me 129X I was able to detect NGC 6332 and NGC 6329. They were really tough, a borderline observation, but I was able to hold them steady enough to draw the, I could not spot any of the other galaxies though.
2147
I tried to locate observations of these galaxies by others, but except for Steve Gottlieb’s observations of the NGC galaxies on the NGC/IC project homepage, http://www.ngcicproject.org/ (using 17.5” and 18” telescopes) I could not find any observations. Steve’s observations were quite similar to mine. Yet, having seen NGC 6332 and 6329 in a 6” achro, I believe that under good conditions a 12” could possibly show at least all the NGCs and even the brightest CGCG galaxies.
Normally, this would have been the end of the article, but as luck would have it, on the very next morning after my 6” observations I accidentally discovered a misplaced stack of old S&T magazines, including the July 2001 issue which contained the article that inspired this week’s Object of the Week. Needless to say, I immediately checked the article to compare my observations with those of Ken Hewitt-White. Well, for the most part we have had similar observations. I did observe a couple of CGCG galaxies that went unobserved by Hewitt-White, yet he did observe some “anonymous” galaxies that were not plotted by Megastar but were visible in the Deep Sky Survey images of the area. I did prepare charts based on the DSS images to track down these anonymous galaxies myself, but work commitments and the appearance of the moon did not allow me to observe them, a project for the next new moon period. In his article, Ken Hewitt-White mentions that under very dark skies he did manage to observe all the NGC galaxies and some of the CGCG ones with his 10-inch dob, confirming what I suspected after observing this area with a 6-inch refractor.
Here is a list of all galaxies mentioned by me in the article above, plus those mentioned by Ken Hewitt-White in his article. I have prepared a DSS image with all sixteen galaxied mentioned. Note that in the S&T article, the CGCG galaxies are labeled under the PGC catalog. In the list both identities are mentioned, as well as the A1-A8 labeling used in the S&T article. To avoid cluttering, on the DSS image I have numbered them from 1 to 16 as listed below.
1 – NGC 6336
2 – NGC 6332
3 – NGC 6329
4 – NGC 6327
5 – NGC 6323
6 - CGCG 225-91 = PGC 59984 = A1
7 – CGCG 225-84 = PGC 59930 = A2
8 – IC 4645 = A3
9 – CGCG 225-87 = PGC 59950 = A6
10 – CGCG 225-70 = PGC 59859 = A8 (note that in the S&T article labeled as PGC 91583)
11 – CGCG 225-81 = PGC 59914 (not in S&T article)
12 – CGCG 225-83 = PGC 59931 (not in S&T article)
13 – CGCG 225-79 = PGC 59912 (not in S&T article), not visible in the DSS image (just off the southern edge of the image).
14 – A4 in S&T article, not observed by me
15 – A5 in S&T article, not observed by me
17 – A7 in S&T article, not observed by me (note that by mistake I labeled it “17” instead of 16, that’s why 16 is missing!)
2148
So, this Object of the Week is more reminescent of a treasure hunt than of a very detailed study of a single object. It certainly gave me lots of pleasure in trying to hunt down these faint fuzzies, and I hope it gives the same pleasure to many others. Although it is most suited for those with medium to large scopes, users of smaller scopes should also attempt it, and should remember that even if they don't manage to locate the galaxies, there is a superb consolidation prize in observing the beautiful M92. And I should express many thanks to Ken Hewitt-White for without his superb article I doubt I would have ever considered searching for faint galaxies around M92!
So, next time you are out, think Hercules and his labors, try this labor for youself, and ...
GIVE IT A GO AND LET US KNOW!