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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12592
Loc: Cumberland, R I , USA42N71.4W
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This is another excellent challenge double. Many should be able to see the 9.6 arcsec uneven pair (Y Del = 4.5-5.5/9.6") with a 15x, but not every night. And also with this one, good focus is critical. I've occasionally seen what looked like a split with 15x70s. 16x makes it just a bit easier. At 20x you should be able to see it all the time. But there is a bonus.
Just southwest of Y Del, the nose of the Dolphin, is another fainter and much closer pair. Struve 2725 is 7.6-8.4/5.8". It is best seen with 25x or more. It's a challenge for 25x.
IIRC, the orientation of these two pairs is similar to the Double-double.
Anyone with a BT, even low powers from 25-30x show this pair nicely separated along with the brighter and more conspicuous Y Del.
My observation
Gamma (12) Delphinus and Struve 2725
Gamma Del, at 4.5-5.5/9.6” the point star of Delphinus, is a double I look at almost every time I’m out. It is an easy double for a 20x80, but will be difficult for a 15x70. Gamma has been cleanly split with a 16x70 Fujinon. I had hoped to see it elongated with the 10x60 but it did not show itself. In the 20x80 it was clearly separated. A little below y Del is a much tighter double, Stf2725, at 7.6-8.4/5.8”, a challenge even for a 25x binocular. I noticed it elongated in a 20x80. It's beautifully split in the BT100 using 20mm TVplossls at 31x.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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GlennLeDrew
professor emeritus
Reged: 06/18/08
Posts: 630
Loc: Ottawa, Ontario, Canada
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I've easily split gamma Del in my 26X100s, but never thought to even try Struve 2725. It sounds like a nice pair of doubles. I'll definitely give it a go!
Speaking of "double doubles", I'm pretty sure you must have enjoyed xi Sco at some time. It's one of my all-time favorites for large binos.
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Mediocre minds discuss people. Good minds discuss events. Great minds discuss ideas.
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rookie
sage
Reged: 01/14/06
Posts: 330
Loc: St. Petersburg, FL
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Thanks for the new targets. I'll check them both out, just need clearer skies and a day off from work so I can be up late enough to see Delphinus.
I've looked at Xi Sco before because it was a recommended double star target in Sky & Tel in the past but I'd forgotten about it this year. 
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Shirley
Celestron CPC 800XLT~Feather Touch
G0 BT80~45degree; Fujinon 16x70 FMT-SX
Celestron Ultima 9x63 & Regal LX 10x42
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ronharper
Pooh-Bah
Reged: 02/14/06
Posts: 1007
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I dark-lined Gamma Del last summer a few times with my 16x70, but never saw the two neat dots I'd like. Stopped down to 40-50mm, it is too easy, it's cheating.
I'll try again later this summer, as soon as the western mountain smoke/cloud/rain season passes.
Glenn thanks for the reminder on Xi Sco. I don't even know if I've looked at it or not. I I'll have to head for a Greek alphabet reference to relate this to the appropriate squiggle.
Ron
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rookie
sage
Reged: 01/14/06
Posts: 330
Loc: St. Petersburg, FL
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This is a nice
Greek alphabet
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Shirley
Celestron CPC 800XLT~Feather Touch
G0 BT80~45degree; Fujinon 16x70 FMT-SX
Celestron Ultima 9x63 & Regal LX 10x42
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ronharper
Pooh-Bah
Reged: 02/14/06
Posts: 1007
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Thanks, Shirley. The double squiggle with the extra wiggle, I hate that one. So, Xi is star in Scorpius right up-tail from the snake eyes. I don't think I have ever seen this one. It's a complex multiple star, but there's an equal 12" pair in there that a 16x ought to split. Can't wait to try it with bino and scope.
Ron
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Mark9473
Carpal Tunnel
Reged: 07/21/05
Posts: 2703
Loc: 51°N 4°E
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Quote:
This is another excellent challenge double. Many should be able to see the 9.6 arcsec uneven pair (Y Del = 4.5-5.5/9.6") with a 15x, but not every night. And also with this one, good focus is critical. I've occasionally seen what looked like a split with 15x70s.
Well, I for one failed tonight with my 15x63 (edit: tripod-mounted!). It was definitely elongated, and at times I seemed to see two "dots" within the elongated glow, but never a clean split.
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Mark
Leica 8x20; Vixen 8x42; Swift 8.5x44, 10x50 and 20x80; TS 7x50; Orion 15x63
WO Megrez II 80 FD + Baader 90° T2 Amici
Edited by Mark9473 (10/02/08 12:39 PM)
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ronharper
Pooh-Bah
Reged: 02/14/06
Posts: 1007
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I looked last night, and as usual dark lined Gamma Del with 16x70, and came closer to a good split stopped down to 60mm, but still no cigar. I know I could get it stopped to 40mm, but at some point this starts to feel really wimpy. I also tried 10x50. At first I thought I could see elongation, but better focusing took care of that illusion.
Mark, I know you are into hand holding your binos, but if you are doing that well on this one with 15x unsupported you must be superman. Even so, if you'd stand on both feet, instead of trying to show off, you might have better luck.
Ron
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Tony Flanders
Carpal Tunnel
Reged: 05/18/06
Posts: 2103
Loc: Cambridge, MA, USA
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Quote:
At 20x you should be able to see it all the time.
That would be better phrased as "at 20x *I* can see it all the time". People vary tremendously in their ability to split tight doubles. For some people, splitting the main components of the Double-Double naked-eye is laughably easy. For most (including me), it's out of the question.
I don't own binoculars capable of splitting Gamma Del for my eyes, but my notes with my 70-mm refractor say "at 19X, a hint of two touching pancakes, but no true split." I need an apparent separation of 4' to split an equal pair reliably with black space between the components, can sometimes split down to 3', never significantly less than that.
I've heard some people claim (apparently truthfully) that they can reliably split an even double with an apparent separation of 1'.
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Tony Flanders
eyeglasses
6x15 and 8x32 monoculars
8x25, 7x35, 10x30 IS, 10x50, and 15x70 binoculars
70mm and 100mm achromatic refractors
4.5", 7", and 12.5" Dobs
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Mark9473
Carpal Tunnel
Reged: 07/21/05
Posts: 2703
Loc: 51°N 4°E
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Quote:
Mark, I know you are into hand holding your binos, but if you are doing that well on this one with 15x unsupported you must be superman.
Ron, I went back and edited my post to clarify that the 15x63 were tripod-mounted!
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Mark
Leica 8x20; Vixen 8x42; Swift 8.5x44, 10x50 and 20x80; TS 7x50; Orion 15x63
WO Megrez II 80 FD + Baader 90° T2 Amici
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