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CityAstronomer
member
Reged: 07/26/07
Posts: 12
Loc: S. California
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Last night I decided to go out and observe double stars with my Cambridge Double Star Atlas given a past 1qtr. moon. After viewing a few doubles, I decided to observe some of the brighter deep sky objects. Enjoying the open cluster M7, I noticed on the Atlas that NGC 6441 was close by and decided to give it a shot. My backyard is in a white zone and I don't usually go that low in my southern sky as I have a shopping center in that area, but it was a transparent night. Well I was very surprised as there it was in my 4 inch refractor at 56x. A nice round soft glow. As I moved up in magnification, I noticed the 10th mag. star close by and the glow grew. I could not resolve any stars, but with avert vision there appeared to be some mottling.
In any case this was a very unexpected suprise on a night where I really was only going after doubles given the conditions. Doing some further research I learned that this is a very bright globular and it has a planetary hidden within it's boundaries. Has anyone ever seen this planetary and if so, what size scope was used and what were the sky conditions needed to see it 
Sam
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Stellarvue 102 f8.75 APO
Super Polaris Mount
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Achernar
Post Laureate
Reged: 02/25/06
Posts: 4981
Loc: Mobile, Alabama, USA
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A planetary nebula in NGC-6441? That's a new one for me, but even if that's true, it would be far beyond a small telescope's reach, and probably beyond a large one's too. M-15 and M-22 have planetary nebulae also, and to see the one in M-15 takes a 12-inch or bigger telescope and a magnification of at least 500X to glimpse it. At that, it's hardly one arc-second across, a very tiny object to see. I find a 5 arc-second planetary nebula to be bad enough, but the planetary nebulae in globular clusters are at immense distances and almost impossible to see visually. NGC-6441 is a highly condensed globular that is also poorly placed for observers in the U.S. The low elevation means bad seeing near the horizon will probably make seeing it impossible even if you had a large telescope at your disposal. NGC-6441 is a remarkable object however, I came across it by accident, and was very surprised at how bright it is. Scorpius has three planetary nebulae that turned out to be easier to see with a 10-inch than I thought despite their low elevation as seen from the U.S. NCG-6153, 6302 and 6072 are fairly easy with nebula filters under less than perfect skies. Also, take a look at NGC-6388, another bright and condensed globular cluster in the same area.
Taras
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15-inch F/4.5 Dob under construction
10-inch F/4.5 Discovery Dob
6-inch F/8 Homebuilt Dob
4 1/4-inch F/4 Homebuilt reflector
A whole bunch of eyepieces, filters and other accessories....
Two curious cats
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JayinUT
I'm not Sleepy
Reged: 09/19/08
Posts: 895
Loc: Utah
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Nice report. I fear that by the time the weather clears up where I live (next Tuesday or so) the moon will be full than wanning gibbious and by the time it gets back past last quarter the clouds will return.
Thanks for posting on NGC 6441. I did some research and found that the planetary is located near the globular's core/center so I would say that most average scopes won't have a chance to pull that out (maybe a very large dob but others can comment/correct me). My information for that came from here.
In case you don't want to click the link here is the info:
Quote:
JaFu 2 (diameter of 5" = 0.22 pc) in NGC 6441 is very likely a cluster member, having similar velocity (37 km/s), and extinction (E_B-V=0.4), in addition to being close to the cluster center (37").
I also found this site where they discuss that a 20" or higher aperture scope is needed with an OIII filter and a very dark site (they list it as perhaps an ultimate, well perhaps one of the ultimate, greatest planetary challenges).
I also found this article on NGC 6441 where the authors discuss the difficulties in labeling NGC 6441 as to what type of globular it is based on the fact
Quote:
that the classification of NGC 6441 into one or the other of the usual Oosterhoff groups is difficult. The long periods of the RRab stars and the relatively large proportion of c-type pulsators are more typical of Oosterhoff II than Oosterhoff I systems, although we again note that 〈Pab〉 is unusually large even for Oosterhoff II. In contrast, the mean luminosity of the NGC 6441 RRc stars, as found by applying the Simon & Clement (1993a, 1993b) method (see § 5.1), is consistent with values found in Oosterhoff I clusters such as M3.
Furthermore in their conclusion the authors state
Quote:
NGC 6441 stands out as one of the more unique globular clusters of our Galaxy. NGC 6441 is confirmed to be a metal-rich globular cluster exhibiting an unusual HB morphology. (and) NGC 6441 was shown to stand apart from other Galactic globular clusters in that it does not fit in the Oosterhoff classification scheme. The mean periods of the RRab stars in the cluster are as long as or even longer than the typical, more metal-poor, Oosterhoff type II clusters. This contradiction in the trend of increasing period with decreasing metallicity for a given amplitude implies that the metallicity-luminosity relationship for RRLs is not universal—if, in fact, the RRLs in NGC 6441 do share the cluster's relatively high overall metallicity.
So, again, I have to thanks for bringing up this globular and allowing me the opportunity to increase my own understanding of the many wonders that this object holds. That is one thing I love about this hobby, the opportunity to learn something everytime I research an object I or someone else has observed and to find out some interesting facts about the object from the scientific community.
Here is a link to the second article incase someone wants it in PDF instead of the HTML I used: HTML or PDF Article
Edit: If your looking for planetary nebula's to view here is a list of summer objects: Planetary Nebula Obervers Guide BTW you can click on the home on the top (horrible midi music) and then go to the left and find seasonal PN's and get more by season or download his database.
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Jay in Utah
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Location: Lat: 40.514N Long: -112.032W
Mortal as I am, I know that I am born for a day. But when I follow at my pleasure the serried multitude of the stars in their circular course, my feet no longer touch the earth.
— Ptolemy, c.150 AD
Jay's Observation Blog
XT6, XT8, XT10
21,17,13mm Stratus
5mm Hyperion
32 Q70
UB NB & OIII Filters
2x Shorty Barlow
Other Stuff
Edited by JayinUT (07/03/09 11:55 AM)
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CityAstronomer
member
Reged: 07/26/07
Posts: 12
Loc: S. California
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Jay, thank you for all the wonderful links and increasing my knowledge further on this globular.
Taras, thank you also for your comments and the reference to NGC 6388. I will look for it on my next clear moonless night.
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Stellarvue 102 f8.75 APO
Super Polaris Mount
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JayinUT
I'm not Sleepy
Reged: 09/19/08
Posts: 895
Loc: Utah
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Found a couple of other links from a member of our local group who does a blog in one of the local papers:
PN GJJC1 in M22 is a hard object. It is 1 arc minute from the core and is lost often in the triad of stars found in the location. Here is a link that will describe the challenges some have had in tracking this object down. Here are finder charts for GJJC1 Finder Chart
A better though very challenging object is Pease 1 in M15 which is probably best viewed come fall. In the constellation of Pegasus (west of 9Pegasi if I remember right). Pease 1 is 13th magnitude and should be able to be seen. Here is the finder charts and information Pease 1 Finder Charts in M15
Here is a copy of Dave Jurasevich's observation of Pease1 Dave J's Observation and a picture from Hubble that really shows the PN: Hubble Image ; the PN is up and to the left, its pinkish.
I think before trying for Pease 1 I am going to continue practicing on some other PN's that are on the border of my seeing. I find that experience helps but like I said, at 13 magnitude I'm not concerned about not seeing it. Cheers!
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Jay in Utah
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Location: Lat: 40.514N Long: -112.032W
Mortal as I am, I know that I am born for a day. But when I follow at my pleasure the serried multitude of the stars in their circular course, my feet no longer touch the earth.
— Ptolemy, c.150 AD
Jay's Observation Blog
XT6, XT8, XT10
21,17,13mm Stratus
5mm Hyperion
32 Q70
UB NB & OIII Filters
2x Shorty Barlow
Other Stuff
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JakeSaloranta
sage
Reged: 09/18/08
Posts: 229
Loc: Sisu, Sauna, Sibelius...
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Quote:
I think before trying for Pease 1 I am going to continue practicing on some other PN's that are on the border of my seeing. I find that experience helps but like I said, at 13 magnitude I'm not concerned about not seeing it. Cheers!
You should be concerned it is no easy task to spot it. Even in your own link Pease 1 is listed at magnitude 14.9 - quite far from magnitude 13. For telescopes 8" and above.
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JayinUT
I'm not Sleepy
Reged: 09/19/08
Posts: 895
Loc: Utah
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To clarify. Our club has a computer controlled 32 inch reflector and with the 32 inch 14.9 at zenith I'm not overly worried about Pease 1. I do feel in my 15 inch truss it will be challenging, but findable. Everything will have to come together, great skies, the right instruments; scope, filter and eyepiece. As stated, I agree they are challenging objects, but I'm just saying I'm more comfortable going for Pease 1 than going for GJJC1. This is based on further information on these sites:
Mike Wirths 25 Obsession Observation Pease 1
Observation in UK Imaging
Observation Reports of Pease 1
Notice in the last report (repeat post from above) there are individuals who have found it in a 8 inch dob from Austria and in a 10 inch dob. Daniel Restemeier from Germany used a 12 inch dob to find it and has an excellent sketch of the M15 and Pease 1 in that report. It may take several attempts as some challenging deep sky objects do and have, but I know that I will get it. To quote from my signature, "It will seem difficult at first, but everything is difficult at first." I'm looking forward to the challenge.
One of our members who writes the blog found GJJC1 on the night/morning of May 28th and feels that others can find it also here in July with the right skies and instruments. I'm not ready for GJJC1 but again, Pease 1 should be attainable, challenging, yes, but attainable in both our groups 32 inch reflector and in my 15 inch truss. I just may try the 10inch as well after locating it in the 15 inch.
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Jay in Utah
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Location: Lat: 40.514N Long: -112.032W
Mortal as I am, I know that I am born for a day. But when I follow at my pleasure the serried multitude of the stars in their circular course, my feet no longer touch the earth.
— Ptolemy, c.150 AD
Jay's Observation Blog
XT6, XT8, XT10
21,17,13mm Stratus
5mm Hyperion
32 Q70
UB NB & OIII Filters
2x Shorty Barlow
Other Stuff
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BillFerris
Carpal Tunnel
Reged: 07/17/04
Posts: 2900
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Pease 1 is a worthy target for deep-sky enthusiasts in search of a good challenge. Here's a link to my observation with the 18 inch: Pease 1 in M15. Large aperture helps but isn't necessary. Experienced observers using moderate aperture with quality optics have tracked down this elusive planetary nebula.
The initial challenge is the seemingly simple task of reconciling the eyepiece view with whichever image of M15's core you choose as your finder chart. I found the trapezium west of M15's core useful in this regard. With the trapezium identified, it was relatively quick work to pull out the crooked line of four stars to the east. Pease 1 lies to the south of the crooked line, between it and the core of the globular cluster. Blinking the field with my OIII filter allowed me to correctly identify Pease 1. It was the only "star" that retained its brightness with the filter in place. The planetary appears stellar at all but "crazy high" magnifications.
Bill in Flag
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Grand Canyon Adventure
Lowering the Threshold
18" Obsession
4.5" Meade 4500
10x50 Swift Audubon
Cosmic Voyage
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