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Ever observed COU1900?

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#1 WRAK

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Posted 27 April 2013 - 02:14 AM

COU1900 (WDS10275+4136) RA 10:27:28 Dec +41:36:04.4 sep 2.4" +6/10mag is one of the stars I suggested to Sissy Haas to fill in gaps in her object matrix. What I did not check are the WDS notes on this double "First: 1981|295deg|1.7. Last: 2010|304deg|2.4. #Obs: 2" - this lack of recorded observations suggest a potential "non exist".
COU1900 is now slowly coming into my field of view slightly below zenith in western direction.
Yesterday I had a first try on it with my 140mm refractor but conditions were really bad: Near full moon backside, NEML about +2.2mag due not only to light pollution and full moon but also to very high humidity and probably some very thin very high hazy clouds. To make things worse seeing was with Pickering 4 rather bad - so I failed.
Even with severe light pollution but otherwise good seeing 130mm aperture should be sufficient for resolving COU1900 despite the big delta-m - if the 2.4" separation from the last recorded observation is correct.
With the 1.7" separation from the first observations resolution would be a bit more difficult - 160mm aperture or even a bit more would then be required to resolve COU1900.
I will try again next time with my 140mm refractor and switch to a bigger aperture if I should fail again despite good conditions.
If you have an opportunity to try COU1900 please do so - Brian Mason from WDS would certainly interested to get another observation for his records.
Wilfried

#2 R Botero

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Posted 27 April 2013 - 05:40 PM

Wilfried

Thanks for posting this. No show for me tonight on this one :bawling:. Conditions were pretty bad with fast passing clouds and poor seeing. I "practised" with 38 Lyn and then HR3701 (WDS 09210+3811) as these have separations and position angles representative of what COU1900 should be. 38 Lyn was a beautiful, colourful split with my 6" refractor at around 250x. :cool: HR3701 came and went with the seeing but the similar magnitude helped in moments of better seeing :jump:. COU1900 was not there for me tonight. Maybe next week if the weather cooperates.
Roberto

#3 WRAK

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Posted 28 April 2013 - 02:22 AM

Roberto, thanks for your report. On next opportunity you may also try nearby (only about 4° distance) BU1074 WDS10355+4539 RA 10:35:31.24 Dec +45:39:13.395 2.5" +7.2/11.2mag - same separation and same delta-m but both components 1.2mag fainter. BU1074 has also only 2 observations in WDS recorded. Required aperture for resolution should be about 165mm.
Wilfried

#4 fred1871

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Posted 28 April 2013 - 07:12 AM

Wilfried, I think the notion that COU 1900 might not be a double because there are only two listed measures is a tad pessimistic. Given that it's a relatively recent discovery (1981), and that the second measure is listed for 2010, I'd think it likely to be a double that hasn't had much attention. There are many of these.

Regarding BU 1074, the WDS lists 5 measures, from 1889 to 1923. My copy of Burnham's catalog of his own doubles gives 2 measures, 1889 and 1899 - the first from 3 nights' measures by Burnham, the second from 2 nights by Aitken. Many doubles' measures are the result of more than one night of measuring, then averaged (possibly weighting some results above others). BU 1074 was discovered with the Lick 36-inch refractor, but should, as you say, be visible with lesser telescopes.

I can't help on these two with observing, because they stay less than 20 degrees above my horizon, where the atmosphere is always a problem.

#5 R Botero

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Posted 28 April 2013 - 08:56 AM

Thank you Wilfried. BU1074 added to my observing list.

#6 WRAK

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Posted 28 April 2013 - 12:12 PM

Fred, would expect neither from Couteau nor from Burnham reporting bogus doubles - but all these discoveries were made with really large refractors and to some degree I can imagine errors concerning the magnitude of the companions.
But we will see.
Roberto - the mentioned required aperture of 165mm for resolving BU1074 is a mean value and this means with good conditions a reasonable good chance also for your 152mm refractor as this is within the standard deviation range.
Wilfried

#7 R Botero

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Posted 30 April 2013 - 02:44 AM

Wilfried
Conditions last night were almost as good as they get up here in SE England and I had a go at COU1900. No show first time so moved to BU1074 and saw it at the first attempt but with difficulty: it was overhead and I was basically sitting on the ground to reach my refractor end and it takes a long time for it to get dark enough up here at 52N to see above mag 10 from my suburban garden.
In any case, the secondary was at roughly 200d PA and I made it pale blue compared to the main yellow-white primary.
I then moved to COU1900 and although I suspect I saw something it wasn't as "clear" as BU1074. Here the companion was 90d CW from where BU1074 was and if I saw it, it looked red compared to the primary which was more white-blue.
I moved to other doubles in Leo after that and when I returned to these later in the evening before packing up I could not improve on the above. I think my seeing and aperture put this pair of doubles at the very edge of what is achievable from my location.
All the above with an AP 6" refractor, Mark IV binoviewers, working at roughly 250x.
Roberto

#8 WRAK

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Posted 30 April 2013 - 04:00 AM

Roberto, great report - as you could resolve BU1074 COU1900 should have been easy in comparison. Your impression of a red hue for the companion could exlain this at least to some degree but I still have the suspicion that the secondary of COU1900 is fainter than advertised. The given +6/10mag are for me a bit too smooth numbers to be true.
Next opportunity I will try again with my 5.5" refractor and if I fail again then with 210 or 235mm Cassegrains scopes.
Which naked eye magnitude limit did you have for this observation?
Wilfried

#9 R Botero

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Posted 01 May 2013 - 02:32 AM

Hi Wilfried
On a good dark winter night, around 5. Two nights ago at the time of observing around 4 max. :bawling:
Roberto

#10 gfeulner

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Posted 01 May 2013 - 03:50 PM

I was able to split COU1900 right away last night with my C8. BU1074 was a no go. Tonight it's suppossed to be better so I'll try again. Gerry

#11 WRAK

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Posted 02 May 2013 - 01:00 AM

Gerry - great news. What was your NEML? Do you remember details like color hue, magnification, estimated separation and position?
Wilfried

#12 gfeulner

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Posted 02 May 2013 - 08:54 PM

Sorry, but I don't know what NEML means? The magnification was 268x and the estimated separation looked to be 1.8-2.0". I'll take a closer looks ASAP and see if I notice any hue. I'm not good at estimating position angle. Gerry

#13 WRAK

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Posted 03 May 2013 - 02:04 AM

Gerry, NEML means Naked Eye Magnitude Limit and is the magnitude of the faintest star your can see without any optical helpers except eyeglasses or contact lenses in your field of view above 45° to zenith.
Concerning position: You can imagine a clock when viewing the double and give the position of the secondary on this clock in terms of hours or better half hours. Given your location and time of observation this clock position can be translated into a crude estimation of position.
Wilfried

#14 gfeulner

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Posted 05 May 2013 - 12:15 PM

Well, I don't know if these old eyes are fooling me but the last two attempts failed at seeing it. The "NEML" was about 3rd magnitude and the seeing was excellent. I'll keep trying. Gerry

#15 Bill Boublitz

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Posted 05 May 2013 - 01:11 PM

Not yet, but it's on my short list. I e-mailed Sissy Haas some months ago asking why we had apparently dropped it from the list. There is much evidence to suggest it is a true neglected double. The only conflict is how S.2, U.2 and the M.S.A. show a single star of approximately 6th magnitude in Cou 1900's exact coordinates.

#16 fred1871

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Posted 05 May 2013 - 10:54 PM

Bill, I wouldn't think the failure to mark it double on Sky Atlas 2000 or Uranometria means much.

But Millenium Atlas marking it single might be meaningful, as that tells us there's no measure from Hipparcos. That's the one thing that does have me uncertain - no 1991 measure.

Of course, if as Wilfried suggests the photometry is wrong for the companion, so it could be much fainter than mag 10.0, it could be beyond the Hipparcos range of stars recorded. So, we need observations to indicate whether it's a viewable double.

Couteau most likely observed with the 30-inch Nice Observatory refractor, and it's possible that the magnitude is an eye estimate. As we've seen elsewhere with Jonckheere doubles, eye estimates can be sometimes very inaccurate, especially with larger telescopes.

The numbers on COU 1900 suggest it should be within range of moderate aperture telescopes, IF the secondary magnitude is near correct. The absence of an Hipparcos or Tycho magnitude suggests it's dimmer. Therefore, the double would, assuming it's real, be tougher.

I've now had a quick look at the AAVSO data (APASS - the photometric survey of m10-17 stars). There's a possible match, a star of V magnitude 10.275 +/- 0.034 that's a potential fit for position, allowing for the recorded error bars on RA and Dec. However, at that magnitude it should be expected to have an Hipparcos measure. So it may be, assuming COU 1900 to be real, that the companion really is dimmer. The positional accuracy of the APASS data isn't high enough to be certain of that star or other stars recorded in that area. Or of whether the APASS system is able to resolve the pair. The nominal pixel size - corresponding to 2.57 arc seconds - suggests resolution at the needed level might not happen, given the 2.4" separation of the 2010 measure.

So, it's back to the telescope for a check on COU 1900.

#17 R Botero

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Posted 06 May 2013 - 01:41 AM

I had yet another go at COU1900 on the night of 3 May. Seeing was not as good as for my previous attempt but decent. I could not locate the companion no matter how hard I tried. That same evening I was doing limiting magnitude measurements for Wilfried using the M67 chart discussed in an earlier thread. I managed to go as faint as mag 12.1 so I was surprised to fail at COU1900 again. Maybe the delta or maybe the companion is fainter as suggested previously.
Roberto

#18 Bill Boublitz

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Posted 06 May 2013 - 10:24 AM

Interesting to read all the posts. I did survey the field with a 4" refractor out of curiosity several weeks ago. In fact, like Wilfried I had split 38 Lyncis earlier in the evening. Observed the suggested COU 1900 primary of roughly mag. 6.0, white/blueish-white in color. A good match for spectral type A2V. No sign of any companion, but it was late, I was fatigued and just scouting the territory for future. Will make another concerted effort, but doesn't seem promising. I'm with Fred and would not doubt Couteau. (And thank you for all the info regarding a star which is inaccessible from your location!) Obviously, the system has undergone changes. Wilfried, did Brian Mason offer anything more on the 2010 log?

#19 WRAK

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Posted 06 May 2013 - 11:01 AM

Bill - see the uploaded txt.file, thats what I got.
Wilfried

Attached Files



#20 7331Peg

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Posted 06 May 2013 - 01:37 PM

I ran down all those links in the WDS text file and didn't come up with anything that is of any help. It does look as though the magnitude of the secondary is in the neighborhood of 11 based on everyone's experience with this thing.

I gave both Bu 1074 and Cou 1900 a shot a few nights ago with my six inch f/10 refractor with mixed results. The seeing was rotten -- lots of hopping and the stars resisted coming to a sharp focus -- but I caught several glimpses of the 11.2 magnitude secondary of Bu 1074 with averted vision at 190x. No luck at all on Cou 1900, but I really need much better seeing than I had. IF the secondary is around 11th magnitude, and IF it's not orange or red, it should be visible in the six inch, at least with averted vision.

Given that the separations are virtually the same, Bu 1074 and Cou 1900 really provide an interesting comparison in how much difference a full magnitude of brightness makes in the primary -- although it would be a huge help to determine what the real magnitude and stellar classification is of the Cou 1900 secondary.


John :refractor:

#21 Bill Boublitz

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Posted 06 May 2013 - 02:11 PM

Thank you! (WRAK)

#22 R Botero

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Posted 06 May 2013 - 05:34 PM

Thanks for your report John. Your experience seems similar to mine. Did you notice any colour in the secondary of BU1074?
Roberto

#23 7331Peg

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Posted 06 May 2013 - 07:28 PM

No, I didn't see any color in Bu 1074's secondary, Roberto, probably because I only saw it with averted vision. I'll try again on a night of better seeing.


John :refractor:

#24 WRAK

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Posted 07 May 2013 - 11:08 AM

So at least the resolution of BU1074 with a 6" refractor seems to be confirmed as rather a limit observation - not bad for a 2.5" +7.2/11.2mag double.
Wilfried

#25 WRAK

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Posted 15 May 2013 - 02:30 AM

Had yesterday a clear night - seems rather rare lately for my location. Seeing was not this good - around Pickering 5. NEML about +3.45mag.
Had despite this a look at COU1900 with a 235mm SCT - the distorted and dancing diffraction pattern did not allow a resolution.
Tried then with the 140mm refractor. The image was better due to less influence of the bad seeing but the diffraction pattern was still distorted and I had the curious experience of a spurious disk slowly changing position within this pattern - had never before this experience. No resolution of any companion although this should be possible with 140mm aperture and the given values for separation and delta_m. But seeing was too bad to take this as evidence that these values are wrong. Have to try again - looks rather good for tonight as the sky is without any clouds now. Have also to try BU1074 myself next time.
The companion of COU1900 seems certainly a bit elusive as Roberto also reported a non split in a private email communication.
Will this get a full turn around again to a suspected "non exist"?
If COU1900 near Mu UMa is in your field of view and you have a scope up from 130mm aperture - please try this one if you have also reasonable fair seeing.
Wilfried






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