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Old 30-06-2016, 06:45 PM
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The Mekon (John Briggs)
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Any triple Globulars?

Ok it is globular cluster season with the milky way arcing overhead at reasonable hours, so I pose this question.

Is there any grouping of globulars that can be observed in an amateur telescope that will show three globular clusters in one field?

There are plenty of "double globulars" of various types, particulary M4 and NGC 6144 - easy with a 6" scope and a magnification of around 30x
NGC 104 (47 Tuc) and 121- one large the other small, and NGC 6528 & 6522 smoking off the spout of the teapot.
But what about a triple in the same field - anyone got one? Must be a galactic cluster and not three imperceptible fuzzes in a distant galaxy.
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Old 05-07-2016, 07:39 PM
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G'day John. Yes, but you have to own something like a NP101. I like that scope so much, because it does things not many others can. There are numerous globular cluster clusters around the sky I can fit into the 31 Nagler. Just to name a few

M22, M28, NGC6638, 6642

M69, M70, NGC6624, 6652

NGC6522, 6528, 6558, 6569, AL3

NGC6522, 6528, 6540, 6553, AL3, Djorg2

M28, NGC6544, 6553

M19, M62, NGC6293, 6304, 6316

M19, NGC6284, 6287, 6293, 6325

M4, M80, NGC6144

M9, NGC6356, 6342
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Old 06-07-2016, 03:38 PM
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Thanks Allan for these combinations. I must say I had not thought about such a radical setup as an NP101 + 31mm Nagler. This would give a field in excess of 4 degrees at a magnification of 18X.
I have spent some time this afternoon with Uranometria 2000 and a pair of dividers!

Many of your combinations are close to this 4 degree mark, so I wonder about the ability to discern a non stellar object at the edge of the field with such a low magnification. That said, you have given me some great observations to make, I like the first and last ones best, M22/ M28/NGC 6638/6642 spans only 3 degrees and I may just make that with an old 32mm erfle I have. I call this eyepiece "the aweful erfle" and it will give a 3.2 degree field at 22X on my 106 Astrotech.
The last triple of M9 NGC 6356/6342 is just on 2 degrees I should have noted myself. This should be possible with my normal wide field setup of the 27mm Panoptic and the 106AT.

thanks again for your time in listing these objects.
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Old 13-08-2018, 04:37 PM
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I am re-visiting this post because it is the time of year for multi-globular viewing! Have waiting some time for a really transparent dark night, and last night fit the bill.
Now in my original post, I did not mention that the globulars must be distinctly recognised as such in the field, so that eliminates some of the fainter objects that Allan has listed.
The best two "triples" have to be:
M9, 6356, 6342
M19, 6284, 6293

Using a 106mm F6.5 refractor, I just managed to view both of these triples, the M9 grouping being the toughest. With a 26mm Nagler, and FL of 695mm, giving 27X and a 3 degree field, the M9 group easily fit in the field, but 6342 was very hard to spot. I had to centre this globular, then hold the position of it in my eye and shift the scope to include the other two. Very tough. Any less magnification would not do.

The M19 group was easier, despite almost taking up the full 3 degree field. All three globulars were easily seen at this magnification.

Anyone else like to take up this challenge?
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Old 13-08-2018, 05:56 PM
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mental4astro (Alexander)
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Interesting proposal, John.

I've been looking over the Morel chart of the LMC, and there's a few triples there, even quads. Visually you'll need a big dob, 16" should do, for some of these. However, it is a busy field, and it will take time.

If using digital setting circles, 30,000 click encoders won't cut it to isolate and identify individual objects as they are too close. If using encoders you'll need a resolution in excess of 350,000 clicks. That will give you the resolution grunt that's needed.
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Old 13-08-2018, 07:45 PM
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Are NGC 6540, DJ-2 & AL-3 observable with 4"?

Hi Allan,

Quote:
Originally Posted by Allan View Post
G'day John. Yes, but you have to own something like a NP101. I like that scope so much, because it does things not many others can. There are numerous globular cluster clusters around the sky I can fit into the 31 Nagler. Just to name a few

M22, M28, NGC6638, 6642

M69, M70, NGC6624, 6652

NGC6522, 6528, 6558, 6569, AL3

NGC6522, 6528, 6540, 6553, AL3, Djorg2

M28, NGC6544, 6553

M19, M62, NGC6293, 6304, 6316

M19, NGC6284, 6287, 6293, 6325

M4, M80, NGC6144

M9, NGC6356, 6342
Though the groups of G.C's you list can be contained in a 31mm T5 field in the refractor, are you actually able to see all those listed in that aperture? I'd think NGC 6540, DJ-2 and particularly AL-3 somewhat ... difficult, in that aperture? Even NGC 6325 would be a very difficult object too.


Best,

L.
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Old 13-08-2018, 08:31 PM
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Nice observing John. I haven't got around to trying myself, too many other observing priorities.
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Old 13-08-2018, 08:37 PM
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Quote:
Originally Posted by ngcles View Post
Hi Allan,



Though the groups of G.C's you list can be contained in a 31mm T5 field in the refractor, are you actually able to see all those listed in that aperture? I'd think NGC 6540, DJ-2 and particularly AL-3 somewhat ... difficult, in that aperture? Even NGC 6325 would be a very difficult object too.


Best,

L.
I think I read once a nice observing report you wrote from somewhere very dark, so I know you can go deep at the eyepiece. All those globs you list are around magnitude 10, so pretty easy for a 4" from pristine skies. Granted though, in the spirit of the challenge, and trying to frame them all in the same field of view, the image scale of each glob is quite small.
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Old 13-08-2018, 10:18 PM
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Hi Allan,

Quote:
Originally Posted by Allan View Post
I think I read once a nice observing report you wrote from somewhere very dark, so I know you can go deep at the eyepiece. All those globs you list are around magnitude 10, so pretty easy for a 4" from pristine skies. Granted though, in the spirit of the challenge, and trying to frame them all in the same field of view, the image scale of each glob is quite small.
I not sure you've quite answered my inquiry (above). For the sake of clarity & simplicity: Have you actually observed/seen/detected NGC 6540, DJ-2 and/or AL3 with your NP101 refractor with the 31mm T5 or indeed, at any other magnification?

Best,

L.
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Old 14-08-2018, 06:51 AM
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The Mekon (John Briggs)
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Quote:
Originally Posted by ngcles View Post
Hi Allan,



I not sure you've quite answered my inquiry (above). For the sake of clarity & simplicity: Have you actually observed/seen/detected NGC 6540, DJ-2 and/or AL3 with your NP101 refractor with the 31mm T5 or indeed, at any other magnification?

Best,

L.
Let's not get too specific Les. Allan's original reply to my post was only a list of Globular Clusters grouped together in reasonably compact fields. The task at hand now is to see which of those groups can actually be observed and with what equipment. One group that does interest me is M4, M80, 6144. This group spans 4 degrees, so the 31 Nagler and NP 101 is one of the few combinations that may pick it up. But 6144 is often difficult to see in the glare of Antares, so can it be observed?
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