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ronharper
scholastic sledgehammer
Reged: 02/14/06
Posts: 986
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It almost seems a shame to look at doubles with the Summer Milky Way up, but I did it, with my trusty 7x50. Here is my night's haul, for others who are tired of excitement, or don't have the dark sky that the Milky Way really needs to pop out at you. None of these are extremely close, but most require more than a cavalier glance, so you might want to pull out your mount or chair, or really bear down and hold her extra steady!
There's a fine string of Doubles (one's a triple actually) running through Draco's head that's familiar to telescope users, but the 7x didn't do half bad. Starting out to the west and working east:
17,16 Dra an easy equal pair, a bit dimmer and wider than the famous nu
21 or mu Dra is strictly telescopic.
nu Dra, a famous binocular showpiece double. Equal, bright, wide.
39 Dra, faint companion seen
47 or omicron Dra, no luck with the 7x50. But, it's so easy with 16x60, I'd guess somebody with really good eyes might get it with 7x. But that secondary is going to be close, and dim dim dim.
The next one I just happened upon, and was so excited because I thought at last I had found something in Ursa Minor. Not to be, however, lying 3 degrees over the line in Draco. Does anybody know a good object in UMi?
31 or psi Dra bright, about a magnitude difference, somewhat close.
delta Cepheus bright, a magnitude or two difference, somewhat close. This, astronomers tell us, is a Delta Cepheid.
16 Cyg the double just west of the Blinking Nebula, just right for 7x. Don't bother looking for the nebula, you're just wasting your time. Stop that!
Finally, another one I just ran up on. I salute whichever real astronomer beat me to it about 300 years ago. I will play the odds, and go with the elder Struve. Star Atlas 2000.0 gives it no number. It is the 6th magnitude star 1.5 degrees NNW of the tip of the arrow, gamma Sagitta. Equal, not close, but dim enough to be interesting. M27, the Dumbell, is in the same field.
What is about the 7x50 that keeps me coming back, settling for less, when other binos show more, or much more? It's the combined facts that it is very easy and fun to use, and yet it shows amazingly much more than the naked eye.
Ron
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VanJan
super member
Reged: 07/09/08
Posts: 111
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You are odds on correct - the elder Struve's supplement catalog. Data from SkyCat 2: STFA 48; 19h 53.4m +20d 20m; 7.2, 7.5 mags; 42.2" sep.; 147 degrees P.A.; both stars spectrum A0. As far as UMi, I'm guessing you mean aside from the obvious pairs and Engagement Ring asterism. You could try Pi#1 aka Struve 1972 at 15h 29.2m +80d 27m. Same source data: 6.6, 7.3 mags; 31.1" sep.; 80 degrees P.A.; primary spectrum G5. Good luck and good viewing!
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ronharper
scholastic sledgehammer
Reged: 02/14/06
Posts: 986
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I didn't think the Fraunhofer at 400x would have any trouble with this one. Thanks for doping it out, and especially for the recommendation of the "obvious pair"(to you!) in UMi, which sounds like a good one for a small binocular.
Ron
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VanJan
super member
Reged: 07/09/08
Posts: 111
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Did not mean my suggestion was obvious. The obvious pairs to which I was refering are: Zeta and Theta; Gamma and 11; Eta and 19; Delta and 24.
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Fiske
Carpal Tunnel
Reged: 03/14/04
Posts: 2057
Loc: Missouri / United States
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Quote:
delta Cepheus bright, a magnitude or two difference, somewhat close. This, astronomers tell us, is a Delta Cepheid.
Ron:
This is an interesting double to watch with binoculars on consecutive evenings because it has a relatively short period (around 5 days, maybe?) and becomes more challenging to split when the primary is brighter and easier when it is dimmer. It is also a lovely color contrast double, though I don't recall offhand if the colors are readily apparent with binoculars. They are apparent, even at low magnification, with a telescope.
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Fiske Miles
Nikon 8x42 LX / 12x50 SE Binos
Mini Borg 60ED, TV-101, AT80Ach, XT-8, C11/CI-700, 22-Inch Dob
Way too many Nagler eyepieces
http://www.fiskemiles.blogspot.com/
www.fiskemiles.com
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Denis
sage
Reged: 12/24/05
Posts: 217
Loc: Rennes, France
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You have in draco, near umi a nice equal double, 40,41 draco which is certainly a challenge for 7x50 at 19" separation.
I split it easily with 10x42 IS, and much less easily with 8x42 on tripod.
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Canon 10x42 IS binoculars.
Meade sc 4" on homemade fork equatorial mount.
homemade 10" an 14" dobsonian
Nikon photogear.
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ronharper
scholastic sledgehammer
Reged: 02/14/06
Posts: 986
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Fiske,
5 days, I think even my attention span can handle that, and will watch it. Thanks for the information.
Denis,
Thanks for a rather tough challenge star in UMi neighborhood. It is beginning to look like observing with nothing more than a 7x50 could keep one rather busy!
Ron
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ronharper
scholastic sledgehammer
Reged: 02/14/06
Posts: 986
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This is an appreciative follow up on the suggestions offered by Fiske, VanJan, and Denis. I was out for a bit tonight.
Delta Cepheus, although well split with 7x50, required 10x50 to see the color contrast--I'd call it yellow for the primary, blue for the secondary.
Pi 1 UMi is not labeled as such on Star Atlas 2000.0. Also known as Sturve 1972, its 31 arcsec separation should be easy for 7x50, but the 0.7 mag difference made it interesting. Still, a clean split could be maintained most of the time.
40,41 Dra, at 19 arcsec, was quite a challenge for 7x50, but the nearly equal components helped. Elongation was immediately seen, but a clear split was evident only about 10% of the time. How I wish I understood this "internal seeing" phenomena, and knew how to control it!
Thanks for the interesting suggestions, guys!
Then, for fun, it being an excellent night, I looked at the North American Nebula in Cygnus. Funny, I saw this thing once at 38x in a 10-inch dob at a very dark site, and counted myself lucky, as it seems to be one of those "challenge" objects, and then sort of forgot about it, figuring it was for other people with really big telescopes. But for the last couple of sky go-rounds, I have often admired the deeply contrasted Milky Way regions around Deneb. They don't look like bright nebulosity through a binocular, but rather like star clouds outlined by dark nebulae. Well, the star chart shows that I have been seeing the North American Nebula all along, and with its help it was easy to see the shapes of the main continent and of Mexico. I preferred the view through the 7x50 to that in the 10x50. Its large size fit the 7x better, and the contrast between bright and dark regions looked slightly deeper. The 7x50 is usually fun mainly because of extreme ease of use, and having to overcome the handicap of low magnification. But viewing such an object on a night with the sky a bit better than 6.0 NELM, and my 6+mm eye pupils, it was a case where the 7x50 is actually ideal.
Ron
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Denis
sage
Reged: 12/24/05
Posts: 217
Loc: Rennes, France
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Quote:
40,41 Dra, at 19 arcsec, was quite a challenge for 7x50, but the nearly equal components helped. Elongation was immediately seen, but a clear split was evident only about 10% of the time. How I wish I understood this "internal seeing" phenomena, and knew how to control it!
Well, well, well. So your next mission will be to report on 59 andromeda :
And if you need a little training for this hard one, you can practice a little on 61 ophiuchus  :
--------------------
Canon 10x42 IS binoculars.
Meade sc 4" on homemade fork equatorial mount.
homemade 10" an 14" dobsonian
Nikon photogear.
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ronharper
scholastic sledgehammer
Reged: 02/14/06
Posts: 986
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Denis,
59 And is a great suggestion, but not to be. I have tried repeatedly with my 7x50. Even with 10x it is not easy. I'm sure I'll try again, though. (Who knows, maybe my eyes got better.)
One observer here has split 59 And with an older model 804 Swift Audubon 8.5x44, occasionally said to give the finest central sharpness of any binocular ever made. (Except for this minor feature I'm sure it's a complete piece of trash and I wouldn't have one if it was given to me, no way. It's kind of ugly for one thing.) That's the best I've heard of.
61 Oph sounds worth a try, a bit harder than 40,41 Dra. Thanks for the suggestion. I'm not sure if I know this star or not, actually. Sometimes I forget the name of the star, but know where it is in the sky. I will check it out next chance. Am I just getting smaller, or is the sky getting bigger?
Ron
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Denis
sage
Reged: 12/24/05
Posts: 217
Loc: Rennes, France
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I try those ones the last night and you are right, 59 and is not an easy one. I split it with the 10x42 IS but not easily.
61 oph comme better, but not so easily than 100 her in my opinion. Differences of magnitude are certainly a significant factor in this play.
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Canon 10x42 IS binoculars.
Meade sc 4" on homemade fork equatorial mount.
homemade 10" an 14" dobsonian
Nikon photogear.
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12485
Loc: Cumberland, R I , USA42N71.4W
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I woud consider 61 Oph considerably easier than 100 Her.
100 Her (14.2") can be resolved only in the best 10x.
61Oph (21") can be resolved at 8x.
The 20x60 Pentax can still see 61 Oph out at 95%. 100 Her is lost at 80-85%.
The Fujinon 16x70 can see 61 Oph at 75% out. 100 Her is lost at 60% out.
The Nikon SE 12x50 can see 61 Oph out at 75%. 100 Her is lost at 50-55% out.
In the Pentax WP II 8x40, 61 Oph can be seen at 40-50% out. 100 Her cannot be seen at all.
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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Wes James
Carpal Tunnel
Reged: 04/12/06
Posts: 2418
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Quote:
The 20x60 Pentax can still see 61 Oph out at 95%. 100 Her is lost at 80-85%.
The Fujinon 16x70 can see 61 Oph at 75% out. 100 Her is lost at 60% out.
The Nikon SE 12x50 can see 61 Oph out at 75%. 100 Her is lost at 50-55% out.
Wow... certainly speaks well for the Pentax's!  That's some good company. Of course, the extra magnification does make a difference.
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Wes
Atlantic Beach, FL
Some bino’s from Miyauchi 5x32 Binon's up through Garrett 20x110 Signature's,
Some telescopes from a Stellarvue 80mm NHNG up through a couple of 8” reflectors…
And a wonderful 4.25" Delmarva Shiefspiegler!
Some good friends, made here on C/N.
Oh- several cats and a wonderful wife!
Anyone want a cat???? :-O
"When your work speaks for itself- Don't Interrupt" -Gamble Rogers
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ronharper
scholastic sledgehammer
Reged: 02/14/06
Posts: 986
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Very interesting Ed. Here's my take on 61 Oph as a test of edge sharpness.
When you take the true fields into account, the Fujinon 16x70(true field 4.0 deg) beats the Pentax 20x60(true field 2.2 deg), despite its lower magnification. But the Nikon 12x50 (true field 5.0 deg) is the real winner, amazing at only 12x.
95% of the way to the edge in the Pentax is 1.05deg off axis.
75% of the way to the edge in the Fujinon is 1.50deg off axis.
75% of the way to the edge in the Nikon is 1.88deg off axis!
Ron
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12485
Loc: Cumberland, R I , USA42N71.4W
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Quote:
Very interesting Ed. Here's my take on 61 Oph as a test of edge sharpness.
When you take the true fields into account, the Fujinon 16x70(true field 4.0 deg) beats the Pentax 20x60(true field 2.2 deg), despite its lower magnification. But the Nikon 12x50 (true field 5.0 deg) is the real winner, amazing at only 12x.
95% of the way to the edge in the Pentax is 1.05deg off axis.
75% of the way to the edge in the Fujinon is 1.50deg off axis.
75% of the way to the edge in the Nikon is 1.88deg off axis!
Ron
FWIW, I did not intend this as a fov sharpness comparison, only as data which shows it is considerably easier to see 61 Oph than it is to see 100 Her. But I'll go along for the moment.
Above is probably a misleading way to look at this. Since field sharpness has far more to do with the Afov of the eyepiece, and not the Tfov of the binocular, then, where 61 Oph can be seen measured off-axis in the eyepiece Afov would give
95% of the way to the edge in the Pentax20x60 is 95% of 43°/2 or 20° off axis.
75% of the way to the edge in the Fujinon16x70 is 75% of 65°/2 or 24° off axis.
75% of the way to the edge in the Nikon12x50 is 75% of 60°/2 or 22.5° off axis.
adding on more point for 61 Oph
60% of the way to the edge in the Fujinon10x50 is 60% of 70°/2 or 21° off axis.
45% of the way to the edge in the Pentax8x40 is 45% of 49°/2 or 11° off axis (at 8x).
FWIW2, the Nikon Prostar 7x50 falls right in line with those mentioned above.
80-85% of the way to the edge in the Nikon7x50 is 80% of 53°/2 or 21.5°-22.5° off axis.
BTW, a better star for testing edge sharpness is nearby theta Serpens, Alya, 22" and more even.
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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Denis
sage
Reged: 12/24/05
Posts: 217
Loc: Rennes, France
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It was the first time I go on 61 oph, and the sky yesterday wasn't good a the low angles. That certainly explain this feeling.
the perfect match between the two components of 100 her, and the aditionnal half magnitude certainly give a better contrast which allow this clear split with the 10 x 42.
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Canon 10x42 IS binoculars.
Meade sc 4" on homemade fork equatorial mount.
homemade 10" an 14" dobsonian
Nikon photogear.
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Fiske
Carpal Tunnel
Reged: 03/14/04
Posts: 2057
Loc: Missouri / United States
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Ron:
I put the 12x50s on the NGC 6826, the Blinking Planetary, this evening. Had them on a tripod. It is not too difficult with that binocular and can be held steadily in averted vision. It can even be made to "blink" in the binos by looking at it and then looking away. At least, under 4.5 mag skies. It looks like a star, of course, not nonstellar. I picked out a few faint stars near 16 Cygni. The fainter of the pair was 9.8 mag. If I really worked at it, I could probably reach about 10 mag with the 12x50s with good transparency from my backyard.
A tried observing the PN with my 8x42 LXs hand held and didn't do very well. I glimpsed it in averted just a few times. I would put the limiting magnitude for the 8x42s at around 8.5 or a tad more. It would be very tough from an urban backyard with 7x50s, but would be doable, I think, from a dark sky site.
I had intended to do a bit more. We have had rain the past few days, but the sky cleared off about 7:00 PM. I made a few observations before getting to this, had a quick look at a few more objects, and by that time (about 90 minutes) all my gear was soaking wet. That is a LOT of dew for an urban location, believe me. A rural site (where the dew is typically ten times worse) would probably have been unmanageable tonight.
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Fiske Miles
Nikon 8x42 LX / 12x50 SE Binos
Mini Borg 60ED, TV-101, AT80Ach, XT-8, C11/CI-700, 22-Inch Dob
Way too many Nagler eyepieces
http://www.fiskemiles.blogspot.com/
www.fiskemiles.com
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ronharper
scholastic sledgehammer
Reged: 02/14/06
Posts: 986
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I tried 61 Oph tonight with my 7x50, and it is a toughie. I did split it, but could only maintain the split about 1% of the time. It was not too hard in an 8x50 finder scope. Silly little finder scopes are so darned simple--no prisms or anything fancy--and despite being terrible in almost every other way, often give killer sharp on-axis view.
In further off-topic news, I could not resist a peek at globular cluster ngc6426, just a half degree north of 61 Oph, being as how the finder was attached to my 5" refractor. Woah, that is one dim cluster! I saw it for dead sure at 85x, but could not see it at any other magnification.
Ron
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12485
Loc: Cumberland, R I , USA42N71.4W
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posted in another thread (by mistake??)
Quote:
I had a hard, although barely successful, time with 61 Oph last night with my 7x50, so I thought I'd try my 8x bino, which is an 8x42 Leica Trinovid BA.
Stars look good in this binocular, and it handled this one very nicely. Two neatly separated points could be seen, not steadily, but most of the time. For extra points, I observed that I could split it cleanly out to 50% of the way to the edge. That's a true 1.88 deg off axis, which ties the Nikon SE 12x50. Ed has argued that that this measure has little to to with the field's appearance. I think it demonstates that the Leica has a very nice sweet spot.
A 30 degree wide apparent region of truly critical sharpness is more than ample for a handheld binocular. If there is any optical compromise to the field center in improving the edge more, or any expense in doing so, it seems like a bad idea to me. I can't see why anybody would strain their eyes to look at the edge of the field of a widefield handheld binocular, instead of pointing it at the object of interest.
Ron
Actually what I said is this has more to do with the Afov of the eyepiece. take a look at the results of yours here.
50% out can see 21". Compare this to the list of 5 or 6 others I showed above.
your binoc here has a 60° Afov. 50% out from center is 15° off axis
So you have critical sharp 15° off axis. This binocular doesn't even come close to most of those figured above which have generally 20° to 22° off-axis.
It would seem the only way any of these are getting a wider Tfov is certainly NOT by using a wider corrected eyepiece, but by putting the eyepieces in lower powered binocular assemblies. Generally lower powered binoculars all have wider sweet spots. This eyepiece is not as well corrected as most of the others listed above, but it's Tfov is wider because it's low power. That is not a valid comparison. Compare the Afov of the eyepieces, 15° off-axis sharp for the trinovid vs 22° sharp for the SE. If the 12x50 SE only had 15° off-axis sharp, it would be a dog.
edz
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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ronharper
scholastic sledgehammer
Reged: 02/14/06
Posts: 986
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Ed,
I yield. What you "see" when you look into a binocular is more important to the experience than what it "does". At least for anybody approaching the lofty status "optofile", which is most of the folks here. So, I will abandon this measure of "true sharp field". It was worth a try!
But I'll stand by my opinion of the value of excellent edge correction in hand held birding binoculars. It is not of much importance. The 15deg half field of critical sharpness in my Leica appears in normal daytime use, ie looking at things not critiqueing the binocular, like a picture window.
I love the 10x50 Fujinon for astronomy, however, partly for its center field sharpness and contrast, but partly because the field is so sharp all over. But, it leaks bright off-axis light so badly that it is no fun for the dusk owl-watching I so much enjoy, and for which a 10x50 ought to be perfect.
What gives? As far as edge correction, my opinion is mostly psychology based, I guess. Blurred tree limbs, and rocks still look very much like tree limbs and rocks, especially to the edge vision. But stars are points. They just have to be points, or something is wrong. A blurred star, even in the edge of view, just doesn't look much like a star at all, and is quite disturbing. As far as stray light resistance, it's quite real, and measurable, I reckon. You can't see much just below a bright sunset horizon with a poorly baffled binocular.
I'm not knocking your reviews at all--I eat them up. This is an astronomy forum, and you do a bang up job in that department. Unique, acutally. But daytime use is so different!
I hate giving the impression of simply defending my own stuff. Hey, I complain about my Fujinon 16x70 more than anybody else here! I wish I did, but I surely don't, have a binocular that is great for everything. And, I imagine, neither do you. To ding a Leica or Zeiss for poor edge correction, or to ding the finest astronomy 10x50 made for poor sunset owling performance, is like dinging a Ferrari because it's hard to see backwards out of while parking, or a Hummer because it won't hang a G on dry asphalt.
Ron
PS sorry about the confusion--I guess this really is a continuation of the discussions in the "Swaro 10x50" thread--it just contained an observation of 61 Oph, so I wasn't sure where to put it.
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