KennyJ
Reged: 04/27/03
Posts: 10155
Loc: Lancashire UK
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Last night , a rare clear(ish)one here in Lancashire , I spent the best part of an hour looking at the Orion nebula through my little collection of scopes and binoculars.
I've read that SOME observers claim to have postively identified the 4th star in the trapezium through Fujinon FMT SX 16 x 70 binoculars , but I have never succeeded through my Helios 15 x 70s.
In fact , even through my 102mm f5 refractor, on nights such as these ,I usually need to UP the magnification to 25x ( using 20mm e.p ) to see the separation from the 3rd component.
Last night , for the first time , added to my little "armoury" of instruments was my Zeiss 85mm Diascope with 20 -60 zoom lens.
At 20x I could NOT make out the 4th star.
Playing around in the dark with the zoom focusser I slowly increased magnification until I could see it ( which took a little settling down time afterwards ),and only checked the actual magnification setting I'd needed when I brought the scope back indoors.
To my surprise ( and a little dissapointment) it was set at well over 30x on the zoom scale.
I'm aware that the "star test" which Henry Link strongly recommended me to try with the scope when I first bought the scope was less than perfect when slightly "out of focus" and am wondering if THIS is the reason it seems to take considerably more magnification with the Zeiss scope than it does with the Chinese 102 refractor ?
Or could this be because it is a ZOOM lens with poorer quality than I might get from a FIXED 20x e.p ?
At the same time , yet again I could make out the 4th component at 25x through the 102mm f5 refractor , even with a relatively inexpensive "extra -wide" e.p.
I still wonder WHAT it is about the Fujinon 16 x 70 that would appear to make this feat seem so much more manageable at such considerably LESS magnification AND significantly SMALLER objective size ?
Is this BECAUSE it is a BINOCULAR ?
Also , I would like to know how many of our members / readers actually HAVE resolved the trapezium in 15x binos ?
Yours expectantly , Kenny
Regards , Kenny
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If everyone is thinking the same thing , no-one is thinking - General George S.Patton
Zeiss 7 x 42 BGAT
Captain's Helmsman 7 x 50
Nikon 10 x 42 Superior E
Swift Audubon Kestrel 10 x 50
Helios 15 x 70 Observation
Strathspey 20 x 90
Televue 76 APO
Zeiss 85 Diascope
Helios 102 f5 refractor
Various eyepieces barlows tripods mounts etc.
Panasonic Lumix DMC - TZ5 digital camera
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Craig Simmons
Carpal Tunnel
Reged: 12/10/03
Posts: 1502
Loc: Falls Church, VA
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I was out the other night with the Obie 20x90s and could only get 3 of 4. It was just rising of the trees in heavy LP, so the seeing wasn't that good.
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Craig Simmons
Oberwerk 8x56, 20x90
Nikon Action IV 10x50
Barska 15x70
Galileo 20x60
Stellarvue 15x63, 20x85
Orion XT10 pre-Classic
Antares 10
Stellarvue AT1010
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12591
Loc: Cumberland, R I , USA42N71.4W
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The Oberwerk 20x80s and the Fujinon 16x70s regularly resolve 3 stars of the Trapezium in M42 and on occasion the 4th component was suspected in the Fujinon 16x70s and Oberwerk 20x80s. On an exceptionally still clear night, that fourth component, the AB component of the Trapezium, at 8.7”, was resolved in the 20x80s at full aperture and also masked at 20x50. The 20x provided just a bit more magnification that allowed easier splitting of this close double than could be accomplished with the 16x70s.
Although I have suspected it, I have never clearly seen AB separated with the Fujinon 16x70. I have suspected seeing the other 3 components resolved with Oberwerk 15x70. The next closest components are separated by 12.9", so there is a significant jump from seeing 3 resolved to seeing all 4 resolved.
The feat you speak of here Kenny is one controlled by the visual acuity of the observer. Even a smaller objective is capable of performing the feat, but not at less magnification than would be required to reach the limiting visual acuity of the observer. An individual who claims to be capable of resolving the 4th component of the Trapezium, at 8.7", with 16x binocuars must have an acuity of 139 arcseconds (16x8.7=139). This would be either questionable or exceptionally noteworthy!
Although 20x binoculars allows splitting closer doubles, it does not allow achieving closer acuity. The closest I have ever achieved with the Fujinons was 154 arcseconds. I've also reached that with the Pentax 16x60s. The closest ever for me with any instrument was 150 arcseconds and that was with the Oberwerk BT100 at 36.5x on a 4.1 second double.
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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AJTony
sage
Reged: 04/17/04
Posts: 379
Loc: Hamilton Square, NJ
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I was determined to see the fourth star with my Canon 15 X 50 IS binos, but have been unsuccessful. Although I have only tried in Central NJ, I have had some very clear nights to check it out. When I tried the 25 X 100's, the fourth star was very obvious.
AJ
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Oberwerk BT100-45 Binos
Apogee 25 X 100 Binos
Canon 15 X 50 IS Binos
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Anonymous
Unregistered
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I have been able to observe the 4th member of the trap with the BT100 at 25x under the darkiest, driest skies I have yet to experience with the BT. In the 'burbs, it has yet to happen at that power.
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12591
Loc: Cumberland, R I , USA42N71.4W
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Based on the visual acuity tests I've performed and the data I've gathered from other individuals, for maybe 80% to 90% of all observers, the minimum magnification required to see a clean split in AB theta 1, the two closest componets of the Trapezium, which are only 8.7 arcseconds apart, would be 18x. More likely, most would not see it unless using 20x.
It is a very small and rare group of observers that would ever be able to cleanly split 8.7 arcseconds with 15x or even 16x magnification. In fact for all the user data I have, no one at all has achieved an apparent speparation of 130 arcseconds, the equivalent of using 15x binoculars to split 8.7 arcseconds.
You can test your own visual acuity limits by observing various doubles with various powers of binoculars. You will find, as you might expect, that as you increase the power of the binocular, you can succeed in splitting closer doubles. What you may not expect to find, but if you choose to do so, testing will prove, is the limit of apparent separation that you can achieve is almost constant across all binocular magnifications.
By that I mean, if your limit with a 20x binocular is a 9 arcsecond double (20x9=180 arcseconds apparent separation), then your limit with a 25x binocular will be very close to 7.2 arcseconds and your limit with a 15x binocular will be close to 12 arcseconds.
Optical deficiencies will diminish these results, so if you only have two or three samples to test, and one is very good while the other two have poor optics, you may not get consistent results. I have gathered my results with more than 20 different binoculars. Twelve of them produced results that vary by less than 3%. Five of them bettered those twelve by anywhere from 4% to 8%. The others were less or have not yet been tested on a double that might show the extreme limits.
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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Henry Link
sage
Reged: 03/31/04
Posts: 316
Loc: Greensboro, NC
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I tried this with a few different instruments; a Takahashi Sky-90 at 20X (couldn't go any lower with the eyepieces at hand), a Takahashi FC-50 at 19X (Nikon zoom EP at 21mm), 17.3X (Swarovski zoom at 23.1mm) and 16X (Zeiss 25mm aspheric) and a pair of Nikon 18X70 binoculars.
The fourth star was easy in the Sky-90 at 20X and in the FC-50 at 19X. It was intermitantly visible in the FC-50 at 17.3X and not visible at 16X. I could see it stably in the FC-50 at a magnification below 19X with the Swaro zoom, but can't be sure about the exact magnification. In the Nikon 18X70 the third componant appeared elongated in the direction of it's companion, but I was not able to acheive a clean split. I suspect the good result with the 50mm Takahashi came from a combination of the near perfect f/8 APO optics combined with the smaller exit pupil, which effectively stopped down the aperture of my own eye's lens, reducing it's imperfections.
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Scott Beith
SRF
Reged: 11/26/03
Posts: 33072
Loc: Gulfport, MS
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I tossed an Orion 32mm Highlight Plossl in my ED80 for 18.75x last night and the 4th star was very easy - even though I was looking at it with the nebula only about 20 degrees above a streetlight.
I tried it with my 12x50 Bushnell's and was unsuccessful. Not even close with the binos.
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  Scott
"The only thing necessary for the triumph of evil is for good men to do nothing." -- Edmund Burke.
"People sleep peaceably in their beds at night only because rough men stand ready to do violence on their behalf." -- George Orwell
"The measure of a man’s greatness is not determined by what he accomplishes for himself, but by what he accomplishes for others.” -- Some Bald Guy
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Thick_asa_Planck
Dark Sky Hunter
Reged: 09/04/04
Posts: 3341
Loc: UK
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A guy at my local astronomy club recently told me that he picked out 4 stars in the trapezium with old 7x50s with perfect optics...he was like "ah, they don't make binoculars nowadays like they used to... 
I assumed it is not possible to see all 4 stars in the Trapezium with 7x50's. Is this assumption correct?
I'm not calling the person i liar, i just...can't think of a way to finish this sentence 
Alex
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It is often commonplace to leave the notation ambiguous - Anonymous
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KennyJ
Reged: 04/27/03
Posts: 10155
Loc: Lancashire UK
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Alex,
Let's just say the guy must have been VERY mistaken.
The four stars HE saw in that area were NOT those making up the trapezium -- but I think I know which "four" stars he probably THOUGHT must form the trapezium.
Just ONE of those stars is actually a part of THE trapezium.
Regards , Kenny
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If everyone is thinking the same thing , no-one is thinking - General George S.Patton
Zeiss 7 x 42 BGAT
Captain's Helmsman 7 x 50
Nikon 10 x 42 Superior E
Swift Audubon Kestrel 10 x 50
Helios 15 x 70 Observation
Strathspey 20 x 90
Televue 76 APO
Zeiss 85 Diascope
Helios 102 f5 refractor
Various eyepieces barlows tripods mounts etc.
Panasonic Lumix DMC - TZ5 digital camera
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12591
Loc: Cumberland, R I , USA42N71.4W
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The gentleman's claim is either mistaken identity or pure BS. There is not a human alive who can claim to have seen the 4 stars of the Trapezium separated with 7x anything, regardless of the size of the objective.
The simple fact of the matter is this. With very few exceptions, human visual acuity for astronomy, the ability to separate point sources of light in a dark sky, requires that the object be magnified so it's apparent size looks to the eye like it is about 120 to 150 arcseconds. For me it's 150. There are very few references in many sources of literature that mention anyone being able to achieve anything better than 120 arcseconds. Personally, I know of no one that has even achieved better than 130 to 140 arcseconds, IIRC.
The closest components in the Trapezium are 8.7 arcseconds apart. So to determine how much magnification you need to see a particular double star split, divide your acuity by the size of the double. For me that means 150/8.7 = 17.2. I need at least 17x to 18x magnification to see all four stars separated. Rest assured, your gentleman friend needs more than 7x. When that person with rare exceptional acuity of 120 arcseconds does come along, still they will need (120 / 8.7 = 13.8) or 14x to see all four.
BTW, a vast majority of people have only 170-180 arcsecond acuity. For them it would take 20x magnification to see all four.
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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KennyJ
Reged: 04/27/03
Posts: 10155
Loc: Lancashire UK
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Ed,
You've probably written that before , but suddenly , possibly because I see it explained as a stand -alone statement , rather than as part of a much longer and more involved text , I fully understand, what is really, as you say, a very SIMPLE matter.
According to your simple formula , I'm estimating my personal arch -second acutity ( PASA would be a fine and useful abbreviation we could ALL use )at a conservative 200 , and it's a very useful , round figure to bear in mind and use as a basic yardstick by which to test myself against in the unlikley event of us ever having a perfectly clear moonless night here in Lancashire before I grow too old to walk out the door.
Regards , and thanks again -- Kenny
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If everyone is thinking the same thing , no-one is thinking - General George S.Patton
Zeiss 7 x 42 BGAT
Captain's Helmsman 7 x 50
Nikon 10 x 42 Superior E
Swift Audubon Kestrel 10 x 50
Helios 15 x 70 Observation
Strathspey 20 x 90
Televue 76 APO
Zeiss 85 Diascope
Helios 102 f5 refractor
Various eyepieces barlows tripods mounts etc.
Panasonic Lumix DMC - TZ5 digital camera
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sftonkin
sage
Reged: 02/25/04
Posts: 395
Loc: Kent, UK
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The closest components, A and B, have a separation of 8.6 arcsec (Hipparcos). A magnification of x7 gives an apparent separation of 60.2 arcsec, or slightly over an arcmin. However, each of these components will have some apparent size (spurious, or Airy, disc), so the "black space" between them will be less than an arcmin.
Now, a standard definition of 20/20 visual acuity is the ability to resolve a spatial pattern with a separation of an arcmin. However, the sort of spatial pattern used is not in any way similar to two points of light against a dark background -- this is much more difficult to resolve -- some people manage about 2 arcmin -- most of us are nearer 3 (or greater). Most people can only just resolve epsilon Lyrae into 2 stars (separation of 3.3 arcmin).
That should be sufficient for you to make up your own mind.
{a few minutes later}
Just read your reply, Ed -- feel free to delete mine if you think I have been overly repetitive of yours.
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Stephen
Hindsight: The only truly diffraction-limited system
Edited by sftonkin (12/16/04 03:52 AM)
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PRESTON
super member
Reged: 10/28/04
Posts: 147
Loc: Haldimand, Ontario, Canada
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Since TrapeziumB is an eclipsing binary, does that make it so dim some nights it is invisible? Last night I took a look at Trapezium with my scope, and I could clearly seperate A,C, and D, but I could not detect B at all. Could star B have been at minima last night?
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15x70 Binocular & Tripod
114/900 EQ Newtonian
150/1200 Dob Newtonian
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12591
Loc: Cumberland, R I , USA42N71.4W
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Stephen,
Your reply supports exactly what I said and is very much worth keeping.
Preston,
All of the stars of the Trapezium remain visible all the time. I'm aware that one of them isvariable, but it only varies from approximately mag5 to mag6. so minima would be mag 6. This does sometimes make it a bit easier to detect the F component.
In order to have difficulty seeing the four components with a scope, you must have been using a very low power. I find all four always visible at 30x and widely separated at 45x.
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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Carol L
Reged: 07/05/04
Posts: 5880
Loc: Tomahawk, WI 45N//89W
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From the Deep Sky Forum,
~Tuesday night Dec 14th~:
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/283758/page/0/view/collapsed/sb/5/o/all/fpart/1
Quote:
I was curious to see whether or not the [22x100] binos would be able to split the main four stars. According to Timothy Ferris, The Trapezium is "scarcely more than a hundred thousand years old" ... just a baby! The A and C stars were definitely split but D and B looked like one star and for the most part I saw a triangle. Then I swung away from the nebulosity to re-check my focus and sure enough, the right eye was a bit off. Going back to the Trap, I now saw the B and D stars as elongated but never did get a clean split.
Sheesh, I even tried pulling the quad to the edge of the fov to make the binos 'squint' but still couldn't get a clean split. An elongation of B and D was the best I could manage.
Maybe next time.
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 *Step-by-Step Lunar Sketching*
CN Gallery
Photo Gallery
8"SCT ~ 120achro ~ 90Mak ~ 80ST ~ 11x70s ~ 22x100s
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sftonkin
sage
Reged: 02/25/04
Posts: 395
Loc: Kent, UK
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Quote:
The A and C stars were definitely split but D and B looked like one star and for the most part I saw a triangle.(...) I now saw the B and D stars as elongated but never did get a clean split.
Sorry to be picky, but I think you are mis-identifying stars here. B and D are separated by more than A and C (about one and a half times as much). It is A and B that are the closest and thus the trickiest to split.
It may be an aid to remember that the four trapezium stars are designated A to D in order of right ascension.
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Stephen
Hindsight: The only truly diffraction-limited system
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Carol L
Reged: 07/05/04
Posts: 5880
Loc: Tomahawk, WI 45N//89W
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The designations are from the Sky Tools program.
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*Step-by-Step Lunar Sketching*
CN Gallery
Photo Gallery
8"SCT ~ 120achro ~ 90Mak ~ 80ST ~ 11x70s ~ 22x100s
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IDONTSEEIT
scholastic sledgehammer
Reged: 05/04/03
Posts: 901
Loc: NYC
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Hey Carol,
Where are E & F ?
Or did they mislable them I & H ?
Now I'm confused 
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Joe,
C8 OTA on UA Unistar Heavy Deluxe
SV-102V on same UA Unistar Heavy Deluxe(not at the same time)
WO-Megrez 80-II ED on UA Microstar Basic
Orion 80ED on same UA Microstar Basic(also not at the same time)
Miyauchi Bs-60ic "Pleiades" 22X60
Orion UltraView 10X50's
Orion MiniGiants 12X63 & 15X63
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sftonkin
sage
Reged: 02/25/04
Posts: 395
Loc: Kent, UK
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You might want to take that up with Greg. The usual designation is that described by Burnham and is illustrated in this drawing from Paul Laughton's site
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Stephen
Hindsight: The only truly diffraction-limited system
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