proud uncle
Carpal Tunnel
Reged: 01/22/07
Posts: 1688
Loc: Central Texas
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I think M40 is the double star in Ursa Major that is also a messier? If yes, is this something resolvable in 10x50s? I think I found it Saturday night, but could not resolve the double. But, I was only hand-holding the binos. Thanks!
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Kenneth
Nikon 10x50 binocular
Zhumell 10" Dobsonian (f/5)
eyepieces: 32mm (2" WA), 20mm, 12.5mm, 9mm (EWA), 6mm (TMB/BO Planetary), and 2X Barlow
Wratten filters: #21, 25A, 47, 56, 80A, and ND13
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Mark9473
Postmaster
Reged: 07/21/05
Posts: 6459
Loc: 51°N 4°E
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Cartes du Ciel says the two components are mag 9 and 9.3, separated by 50 arc seconds. The separation should be easy, but the brightness may be difficult on certain nights (Full Moon etc.).
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Mark
Leica 8x20; Nikon 7x35; Vixen 8x42; Orion 15x63; Docter 15x60
WO Megrez II 80 FD / APM 107mm f/6.5 / Mewlon 210 on DM-6 + Berlebach Planet
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 18806
Loc: Cumberland, R I , USA42N71.4W
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The two components are of visual magnitudes 9.0 and 9.3, and their separation is 49 arcseconds. This one although wider, due to the faint magnitude might be considerably more difficult than the double we were discussing last week in the center of the Pleiades. That one is mag 8 pair at 39 arcseconds. I could not resolve it handheld with any binocular up to 15x.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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KennyJ
The British Flash
Reged: 04/27/03
Posts: 20139
Loc: Lancashire UK
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< Cartes du Ciel says the two components are mag 9 and 9.3, separated by 50 arc seconds. >
Mark ,
Given the figures Cartes du Ciel came up with the other night for those angular separations , I was expecting figures more akin to components of mag 8.99763 and 9.29986 with a separation of 49.9762 arc seconds ! :-)
By the way , no response yet from our more " scientific " brethren on my " movement speculation " !
Regards , Kenny
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Milton Wilcox R.I.P
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 18806
Loc: Cumberland, R I , USA42N71.4W
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Kenny, the only observers that really need to be concerned with fast movement are double star observers. And generally, they need only be concerned with fast moving binaries where one star rotates around the other at a fairly fast rate. Those stars that are near the limit of resolution of our scopes can be seen to sometimes be inseperable and just a few years later can be wide enough to see clearly separated.
On the broad scale of things, Star maps need to be reprinted every 50 years as the coordinates of all objects will have changed enough to be no longer on the same spot on the chart. However, while it's true that everything is moving and quite often in different directions, most objects are not seen to change appreciably with respect to each other.
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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Tony Flanders
Postmaster
Reged: 05/18/06
Posts: 8212
Loc: Cambridge, MA, USA
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Quote:
I think M40 is the double star in Ursa Major that is also a messier? If yes, is this something resolvable in 10x50s? I think I found it Saturday night, but could not resolve the double. But, I was only hand-holding the binos. Thanks!
I've noted it as visible but not really resolved in my 10x50's and even in my image-stabilized 15x45's (back when I still owned them). I think this may be a case where you can duplicate the observation that got M40 included in a list of DSOs in the first place, of seeing a not-quite-resolved double star as a cloud of light.
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Tony Flanders
First and foremost observing love: naked eye.
Second, binoculars.
Last but not least, telescopes.
And I sometimes dabble with cameras.
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 18806
Loc: Cumberland, R I , USA42N71.4W
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here's another very interesting double, actually triple, but the challenge of note here is the faint double. Perfect for this time of year.
10 Mon, 5.1-9.3/77”, C=9.3/81”, BC= 9.3-9.3/21”, outstanding triple in o.c. 2232
this is a long isocoleces triangle. You can see both B and C are nearly equidistant from A. However, B and C are separated by only 21". At mag 9.3, they are a difficult pair. They are similar in magnitude to the components of M40, but much closer.
In 10x50s you would see BC as one and A as the other. Separating B from C is a job for something like a 20x80 or 25x100.
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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Mark9473
Postmaster
Reged: 07/21/05
Posts: 6459
Loc: 51°N 4°E
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Quote:
Given the figures Cartes du Ciel came up with the other night for those angular separations , I was expecting figures more akin to components of mag 8.99763 and 9.29986 with a separation of 49.9762 arc seconds ! :-)
Kenny, angular distance between two points on a sphere is simple geometry; has nothing to do with software. Hipparchos made sure we have many stars' positions with sub-arcsecond precision. Why do you question (again) that angular distance can be given to the nearest arc second or better (admittedly for a given epoch)?
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Mark
Leica 8x20; Nikon 7x35; Vixen 8x42; Orion 15x63; Docter 15x60
WO Megrez II 80 FD / APM 107mm f/6.5 / Mewlon 210 on DM-6 + Berlebach Planet
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KennyJ
The British Flash
Reged: 04/27/03
Posts: 20139
Loc: Lancashire UK
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Mark ,
I don't know if you're misunderstanding me here , but I'm not actually QUESTIONING anything about the capability of measuring angular distances VERY precisely -- although I must admit to being vaguely intrigued by the necessity for it , practically speaking . :-)
-- which is not really the same thing !
Regards , Kenny
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Milton Wilcox R.I.P
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Mark9473
Postmaster
Reged: 07/21/05
Posts: 6459
Loc: 51°N 4°E
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Well determining FOV to better than 1 arc minute is certainly possible, so how would you have me round off the arc seconds?
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Mark
Leica 8x20; Nikon 7x35; Vixen 8x42; Orion 15x63; Docter 15x60
WO Megrez II 80 FD / APM 107mm f/6.5 / Mewlon 210 on DM-6 + Berlebach Planet
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KennyJ
The British Flash
Reged: 04/27/03
Posts: 20139
Loc: Lancashire UK
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Mark ,
You can round off your figures anyway you like for me , my friend , but for ME , accurate to a tenth of a degree , as in 2.3 degrees or 3.5 degrees , is close enough to tell me what I like to know , in advance , providing the figure is ACCURATE , and not just as STATED .
Regards , Kenny
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Milton Wilcox R.I.P
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starramus
Pooh-Bah
Reged: 09/01/04
Posts: 1124
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Quote:
-- although I must admit to being vaguely intrigued by the necessity for it , practically speaking . :-)
I do not see the necessity of this heated exchange over essentially the dimensions of a gnats posterior. 
Burnham's Celestial Handbook (1978)often described as dated and obsolete gives the separation at 50.1 arc seconds with magnitudes of the components at 9.0 and 9.3. The PA is given as 83 degrees with the notation that when originally measured in 1863 by A. Winnecke it measured 88 degrees. This showed a linear decrease which can be easily calculated to a current PA. These trivial numbers demonstrate that they do not merit this exercise in escalation dominance.
Where is that chums graemlin i have seen? 
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hallelujah
Post Laureate
Reged: 07/14/06
Posts: 3980
Loc: Colorado Rocky Mountains
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star,
You are getting kinder as you get older.
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Fujinon12x60HB+Pentax16x60PCFWP+Pentax20x60PCFWP+Pentax20x60PCFWPII
Tento20x60USSR+Orion12x63MiniGiant+Spectrum I 20x65+Orion15x70LittleGiant II
Orion20x70LittleGiant II+Orion16x80Giant+Orion30x80MEGAView+Barska30x80X-Trail
BurgessOptical20x90SeriesII
Edited by hallelujah (04/02/07 09:42 PM)
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