Ever observed COU1900?
Posted 27 April 2013 - 02:14 AM
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.
Posted 27 April 2013 - 05:40 PM
Thanks for posting this. No show for me tonight on this one . 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. HR3701 came and went with the seeing but the similar magnitude helped in moments of better seeing . COU1900 was not there for me tonight. Maybe next week if the weather cooperates.
Posted 28 April 2013 - 02:22 AM
Posted 28 April 2013 - 07:12 AM
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.
Posted 28 April 2013 - 12:12 PM
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.
Posted 30 April 2013 - 02:44 AM
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.
Posted 30 April 2013 - 04:00 AM
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?
Posted 01 May 2013 - 02:32 AM
On a good dark winter night, around 5. Two nights ago at the time of observing around 4 max.
Posted 01 May 2013 - 03:50 PM
Posted 02 May 2013 - 01:00 AM
Posted 02 May 2013 - 08:54 PM
Posted 03 May 2013 - 02:04 AM
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.
Posted 05 May 2013 - 12:15 PM
Posted 05 May 2013 - 01:11 PM
Posted 05 May 2013 - 10:54 PM
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.
Posted 06 May 2013 - 01:41 AM
Posted 06 May 2013 - 10:24 AM
Posted 06 May 2013 - 11:01 AM
Posted 06 May 2013 - 01:37 PM
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.
Posted 06 May 2013 - 05:34 PM
Posted 06 May 2013 - 07:28 PM
Posted 07 May 2013 - 11:08 AM
Posted 15 May 2013 - 02:30 AM
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.