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WRAK
Pooh-Bah


Reged: 02/18/12

Loc: Vienna, Austria, Europe
Ever observed COU1900?
      #5825646 - 04/27/13 03:14 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


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R Botero
Pooh-Bah


Reged: 01/02/09

Loc: Kent, England
Re: Ever observed COU1900? new [Re: WRAK]
      #5826920 - 04/27/13 06:40 PM

Wilfried

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.
Roberto


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WRAK
Pooh-Bah


Reged: 02/18/12

Loc: Vienna, Austria, Europe
Re: Ever observed COU1900? new [Re: R Botero]
      #5827734 - 04/28/13 03:22 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


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fred1871
scholastic sledgehammer


Reged: 03/22/09

Loc: Australia
Re: Ever observed COU1900? new [Re: WRAK]
      #5827862 - 04/28/13 08:12 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.


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R Botero
Pooh-Bah


Reged: 01/02/09

Loc: Kent, England
Re: Ever observed COU1900? new [Re: WRAK]
      #5827993 - 04/28/13 09:56 AM

Thank you Wilfried. BU1074 added to my observing list.

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WRAK
Pooh-Bah


Reged: 02/18/12

Loc: Vienna, Austria, Europe
Re: Ever observed COU1900? new [Re: R Botero]
      #5828329 - 04/28/13 01:12 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


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R Botero
Pooh-Bah


Reged: 01/02/09

Loc: Kent, England
Re: Ever observed COU1900? new [Re: WRAK]
      #5831558 - 04/30/13 03:44 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


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WRAK
Pooh-Bah


Reged: 02/18/12

Loc: Vienna, Austria, Europe
Re: Ever observed COU1900? new [Re: R Botero]
      #5831581 - 04/30/13 05:00 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


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R Botero
Pooh-Bah


Reged: 01/02/09

Loc: Kent, England
Re: Ever observed COU1900? new [Re: WRAK]
      #5833622 - 05/01/13 03:32 AM

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


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gfeulner
sage
*****

Reged: 11/23/07

Loc: Bergen county, New Jersey
Re: Ever observed COU1900? new [Re: WRAK]
      #5834772 - 05/01/13 04:50 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

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WRAK
Pooh-Bah


Reged: 02/18/12

Loc: Vienna, Austria, Europe
Re: Ever observed COU1900? new [Re: gfeulner]
      #5835578 - 05/02/13 02:00 AM

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


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gfeulner
sage
*****

Reged: 11/23/07

Loc: Bergen county, New Jersey
Re: Ever observed COU1900? new [Re: WRAK]
      #5837330 - 05/02/13 09:54 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

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WRAK
Pooh-Bah


Reged: 02/18/12

Loc: Vienna, Austria, Europe
Re: Ever observed COU1900? new [Re: gfeulner]
      #5837613 - 05/03/13 03:04 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


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gfeulner
sage
*****

Reged: 11/23/07

Loc: Bergen county, New Jersey
Re: Ever observed COU1900? new [Re: WRAK]
      #5841659 - 05/05/13 01:15 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

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Bill Boublitz
super member


Reged: 05/04/13

Re: Ever observed COU1900? new [Re: WRAK]
      #5841756 - 05/05/13 02:11 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.

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fred1871
scholastic sledgehammer


Reged: 03/22/09

Loc: Australia
Re: Ever observed COU1900? new [Re: Bill Boublitz]
      #5842698 - 05/05/13 11:54 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.

Edited by fred1871 (05/06/13 03:49 AM)


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R Botero
Pooh-Bah


Reged: 01/02/09

Loc: Kent, England
Re: Ever observed COU1900? new [Re: fred1871]
      #5842881 - 05/06/13 02:41 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


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Bill Boublitz
super member


Reged: 05/04/13

Re: Ever observed COU1900? new [Re: R Botero]
      #5843319 - 05/06/13 11:24 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?

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WRAK
Pooh-Bah


Reged: 02/18/12

Loc: Vienna, Austria, Europe
Re: Ever observed COU1900? new [Re: Bill Boublitz]
      #5843392 - 05/06/13 12:01 PM Attachment (31 downloads)

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


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7331Peg
Sirius Observer
*****

Reged: 09/01/08

Loc: North coast of Oregon
Re: Ever observed COU1900? new [Re: WRAK]
      #5843744 - 05/06/13 02:37 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


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Bill Boublitz
super member


Reged: 05/04/13

Re: Ever observed COU1900? new [Re: WRAK]
      #5843789 - 05/06/13 03:11 PM

Thank you! (WRAK)

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R Botero
Pooh-Bah


Reged: 01/02/09

Loc: Kent, England
Re: Ever observed COU1900? new [Re: 7331Peg]
      #5844170 - 05/06/13 06:34 PM

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


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7331Peg
Sirius Observer
*****

Reged: 09/01/08

Loc: North coast of Oregon
Re: Ever observed COU1900? new [Re: R Botero]
      #5844383 - 05/06/13 08:28 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


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WRAK
Pooh-Bah


Reged: 02/18/12

Loc: Vienna, Austria, Europe
Re: Ever observed COU1900? new [Re: 7331Peg]
      #5845408 - 05/07/13 12:08 PM

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


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WRAK
Pooh-Bah


Reged: 02/18/12

Loc: Vienna, Austria, Europe
Re: Ever observed COU1900? new [Re: WRAK]
      #5861442 - 05/15/13 03:30 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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7331Peg
Sirius Observer
*****

Reged: 09/01/08

Loc: North coast of Oregon
Re: Ever observed COU1900? new [Re: WRAK]
      #5863586 - 05/16/13 12:26 AM

I took another run at this last week with a C9.25 and I "think" I picked out the secondary with direct vision, but I really need to see it a second time before I'm confident it was there. The seeing hasn't been at all cooperative, and the weather looks like it's not going to cooperate either for the next week.

I did confirm Bu 1074 in the SCT with direct vision that night.


John


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WRAK
Pooh-Bah


Reged: 02/18/12

Loc: Vienna, Austria, Europe
Re: Ever observed COU1900? new [Re: 7331Peg]
      #5863719 - 05/16/13 02:54 AM

John, this gets quite interesting now - resolution of BU1074 but not COU1900 in the same session strongly indicates that the advertised magnitude of COU1900 has to be wrong if we still consider COU1900 not as bogus.
Last night I tried myself again with my 140mm refractor with NEML +3mag and Pickering ~6. Could not resolve COU1900 but this could be the effect of the not this good seeing. Could also not resolve BU1074 but for this I would anyway need perfect seeing to resolve this with 140mm.
Have to get more familiar with my C925 to try this with confidence.
Wilfried


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R Botero
Pooh-Bah


Reged: 01/02/09

Loc: Kent, England
Re: Ever observed COU1900? new [Re: 7331Peg]
      #5863934 - 05/16/13 08:59 AM

I had a similar experience. I seem to have been able to resolve BU1074 much more "easily" than COU1900 of which I am not sure about. John, did you manage to see any colour in the companions of either?

Roberto


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7331Peg
Sirius Observer
*****

Reged: 09/01/08

Loc: North coast of Oregon
Re: Ever observed COU1900? new [Re: R Botero]
      #5864759 - 05/16/13 02:49 PM

No, no color seen in the secondary of either Bu 1074 or Cou 1900. For that I'll need more stable seeing than I've had.

I've noticed the colors of the primaries in the two stars are a big factor here. That of Bu 1074 leans toward orange (K2), while that of Cou 1900 is bright white (A2), plus it's 1.2 magnitudes brighter (6.0) than Bu 1074 (7.2). At any rate, that white glow is much harder to see past than the softer glow of Bu 1074.

So I have a feeling that's a big part of the reason we're having more difficulty with Cou 1900. That would also make the secondary seem fainter than it is, at least in comparison to our experiences with Bu 1074. Of course it's still possible that the secondary of Cou 1900 actually is 11.0 instead of the 10.0 listed for it, which all but puts it out of reach.

Wilfried, I'm using a two-speed external focuser on my C9.25. Without it, I don't think I could see the secondary of either of these stars unless I just happened to get lucky. I found the focus had to absolutely precise to see either of the secondaries -- just a slight turn of the fine focus knob in either direction and I would lose them.


John


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WRAK
Pooh-Bah


Reged: 02/18/12

Loc: Vienna, Austria, Europe
Re: Ever observed COU1900? new [Re: 7331Peg]
      #5864822 - 05/16/13 03:19 PM

Quote:

...Wilfried, I'm using a two-speed external focuser on my C9.25. Without it, I don't think I could see the secondary of either of these stars ...



John, I share this opinion - the idea to change focus by moving the primary (or in some cases the secondary) mirror seems rather strange to me. In best case (means without any noticeable focus shift) this could give the performance of a single speed focuser certainly not of good use for double star resolving.
Concerning colors: My eyes must be rather bad in this regard. Only in a few very evident cases I can name colors especially yellow and orange - thats it. Most stars seem to be only creamy white to me. But this is may be also a result of my current focus on limit aperture for resolving unequal doubles.
Wilfried


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WRAK
Pooh-Bah


Reged: 02/18/12

Loc: Vienna, Austria, Europe
Re: Ever observed COU1900? new [Re: WRAK]
      #5890173 - 05/29/13 03:05 AM

Last night to my surprise a clear sky, rather dark for my location with NEML +3.5mag. Seeing depending on scope rather stable with Pickering 5-7 but high humidity gave brighter stars a halo and fainter stars got fuzzy blobs with higher magnification - so not this good conditions for splitting unequal binaries. Tried first with the C925 after checking collimation with Duncam mask - got a hint for a slight miscollimation but the rods did some dancing of their own so this was not conclusive. A Donut mask produced a quite concentric diffraction pattern so I did not change anything.
COU1900 was rather fuzzy at x335 (and even more at 470) and I could not see any companion. Then I tried BU1074 and had the impression of a brighter primary despite +7.2mag should be noticeable fainter than +6mag. But again no resolution here - only when moving the object with slow motion controls over the field of view (this sometimes helps me resolving tight doubles) I got a hint of a companion at 4:30 o'clock in alt/az-mode meaning translated into degrees about 120. But I think this was rather an effect of the mentioned slight miscollimation and anyway in the wrong position as I checked afterwards.
Tried then with the 140mm refractor with quite an improvement in image quality due to the smaller aperture but both COU1900 and BU1074 were at x280 already quite fuzzy with no chance for detecting a faint companion.
Wilfried


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fred1871
scholastic sledgehammer


Reged: 03/22/09

Loc: Australia
Re: Ever observed COU1900? new [Re: WRAK]
      #5891407 - 05/29/13 09:43 PM

Wilfried, your experience with these pairs is a reminder that good seeing conditions, as well as dark sky, are needed for doubles - indeed, steady air and no bloating of star images matter more than sky darkness.

I expect both these doubles, COU 1900 and BU 1074 need good conditions to be seen. COU 1900 may turn out to be the more difficult if the photometry is misleading, and the companion a lot dimmer than the current listing.

As I've mentioned, these doubles are always low in my sky so I won't get an atmosphere that allows me to see them as doubles. Higher in the sky, I've observed a few pairs similar to BU 1074, and was able to see the secondary star in each case with my 140mm refractor. But it does always depend on the atmosphere allowing that to happen: these are not easy doubles for 140mm.

235mm should be better, if collimated, thermally stable, and the atmosphere is good - but my recent observing, including various doubles looked at with both 140mm and 235mm, does not always show a benefit to the larger aperture. With pairs like this it's near-equal. With very close bright doubles, fairly close dim doubles, and not-too-close pairs with very dim secondary stars, the 235mm pulls ahead. Aperture wins, but only for some doubles, and under good conditions.

I'll write up the details of the comparisons fairly soon, when I've done some more observing of the same pairs with both telescopes.


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Nucleophile
super member


Reged: 05/24/13

Loc: United States
Re: Ever observed COU1900? new [Re: WRAK]
      #5908526 - 06/07/13 06:33 PM

I traveled to an alternate viewing spot a few days ago with my gear to get this one.
Observed with a f/5.9 8 inch reflector on a night of good seeing (Pickering 7) I recorded the following:

340x(3.5mm Pentax XW): transiently observed as resolved to two objects;
390x(3.5mm Pentax XW + Paracorr type1): right at the border of resolved and split; the Paracorr sharpened the image just enough to allow this vs viewing with the Pentax alone
400x(3mm Radian): split suspected a few times but cannot definitively state as such.

This object was fairly tough in this instrument on this night ( I blame my troubles on the swarming mosquitos )


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Nucleophile
super member


Reged: 05/24/13

Loc: United States
Re: Ever observed COU1900? new [Re: Nucleophile]
      #5908542 - 06/07/13 06:42 PM

Should have mentioned in the last post the NELM for this observing site is ~5.7.

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Nucleophile
super member


Reged: 05/24/13

Loc: United States
Re: Ever observed COU1900? new [Re: Nucleophile]
      #5908547 - 06/07/13 06:46 PM

I have been able to use my 15" reflector to get pictures of doubles with this mag difference/separation before with my Nikon on a steady night when I can get longer exposures---this should help to tell us if the companion is a phantom. For that matter, it should be a breeze with my 15" reflector---to bad it is in a bad place requiring travel--but now I have my excuse!

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Bill Boublitz
super member


Reged: 05/04/13

Re: Ever observed COU1900? new [Re: Nucleophile]
      #5908984 - 06/07/13 11:25 PM

Very happy to read your post, Mark. I have remained hopeful something could be gleaned for this neglected double, but reports suggest changes in the system or perhaps inaccuracies in the ephemera. NELM 5.7 should be more than adequate for this pair. Your report is inspiring. Thank you for taking the time to go out there and look!

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WRAK
Pooh-Bah


Reged: 02/18/12

Loc: Vienna, Austria, Europe
Re: Ever observed COU1900? new [Re: Bill Boublitz]
      #5909528 - 06/08/13 10:43 AM

Mark, interesting report. Pickering 7 and NELM +5.7mag should be sufficient to resolve COU1900 with a 6" refractor with the given parameters with ease so it should be even easier with an aperture of 8" even if a reflector. The first diffraction ring with 8" should be in a distance of 1" so there should be enough room for the 2.4" separated companion to be seen. It should be fainter as the first ring but much brighter than the second ring and sit somewhat outside the 3rd ring so there is no competition with the diffraction pattern even with a slight jumping in the seeing according to Pickering 7.
May be the fast f/5.9 is a topic here and not even a coma corrector is of much help?
Mark - if you ever have this opportunity again please have also a look at nearby BU1074. If you can resolve this one (same separation but primary and secondary +1.2mag fainter) but not COU1900 than this would be more or less proof of an error in the advertised WDS data.
Wilfried


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Re: Ever observed COU1900? new [Re: WRAK]
      #5910196 - 06/08/13 06:11 PM

I will be certain to observe Bu1074 when I re-examine COU1900.

Ideally, I would like to also image both of these as part of the data collection.
Hopefully next weekend (or sooner).


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Re: Ever observed COU1900? new [Re: Nucleophile]
      #5916919 - 06/12/13 12:52 PM

Quote:

I traveled to an alternate viewing spot a few days ago with my gear to get this one.
Observed with a f/5.9 8 inch reflector on a night of good seeing (Pickering 7) I recorded the following:

340x(3.5mm Pentax XW): transiently observed as resolved to two objects;
390x(3.5mm Pentax XW + Paracorr type1): right at the border of resolved and split; the Paracorr sharpened the image just enough to allow this vs viewing with the Pentax alone
400x(3mm Radian): split suspected a few times but cannot definitively state as such.

This object was fairly tough in this instrument on this night ( I blame my troubles on the swarming mosquitos )




It seems I have to retract this observation. Not only can I not duplicate this observation (albeit from my home site), but I now know that this instrument produces an artifact at high magnification in the vicinity of the position angle where the secondary is said to be found. I had not been using this instrument for these type of studies until recently.

I apologize for this.

I had the same issue with 26 Draconis, which also has a position angle around 300-310 degrees.

The good news is that this artifact likely did not compromise my views of the companions of 42 Ori and Gamma Equ--two binaries I reported on previously whose results have been sent to Sissy Haas. Of course, I will be keen to observe them again in the coming months. Fortunately, the result for COU 1900 was not yet presented to Sissy.

Here is the interesting part: I attempted several careful observations of both COU 1900 and Bu 1074 with my 15" reflector and can definitively state I do not see what is purported by the latest data--clearly something has changed and/or there are errors.

I will be presenting this later information along with positive observations (and an image) of a very similar system (STT 344 in HER) in a separate post within a few days.


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Bill Boublitz
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Re: Ever observed COU1900? new [Re: Nucleophile]
      #5917233 - 06/12/13 03:41 PM

Thanks for staying on this, Mark. I had remained hopeful though pessimistic. If the data were accurate, this object would be little challenge for a 4" instrument. You might forward your negative to Sissy. We should remove it from the list. Perhaps someone could suggest another to take it's place in the table? Wilfried.... is that you?

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Re: Ever observed COU1900? new [Re: Bill Boublitz]
      #5917319 - 06/12/13 04:37 PM

Bill - basically I agree but not to full content.
It seems that COU1900 is dubious but the data for BU1074 is as far as I can see very solid - so the double negative report from Mark makes me cautious. A positive on BU1074 and a negative on COU1900 would have been more convincing.
Alternatives for COU1900 are scarce. BU1074 would be one but seems already a bit on the faint side compared with the other Haas project objects.
Other possibilities are all a bit fainter than COU1900 (and I have found no brighter doubles with ~2.5" sep and delta_m of 4mag):
WDS ID Name RA DEC M1 M2 Sep Con Notes
WDS23243+8625 HO200, IDS23244+8552, BDS12403, ADS16759, BD+85 00399 23h 24m 21s +86:25:04 6,65 10,61 2,4 Cep RA PM:-23, Dec PM:16, AB. First: 1885|138deg|1.7. Last: 1991|152deg|2.4. #Obs: 9. Note Code: D.
WDS16408-7218 HDO255, IDS16292-7206, CP-72 01971 16h 40m 47s -72:17:59 6,67 10,6 2,4 Aps RA PM:20, Dec PM:30, AB. First: 1897|235deg|2.8. Last: 1991|253deg|2.4. #Obs: 5. Note Code: D.
WDS12223-7330 FIN198, IDS12165-7257, CP-72 01240 12h 22m 15s -73:30:13 6,76 10,8 2,5 Mus RA PM:-58, Dec PM:-12, AB. First: 1933|108deg|2.1. Last: 1991|102deg|2.5. #Obs: 4. Note Code: D.
WDS16523-2536 SEE291, IDS16461-2526, BDS7773, ADS10232, CD-25 11743 16h 52m 16s -25:36:02 6,9 11 2,5 Sco RA PM:22, Dec PM:-10, AB. First: 1897|7deg|2.6. Last: 1961|359deg|2.5. #Obs: 5.
Wilfried


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Re: Ever observed COU1900? new [Re: Bill Boublitz]
      #5917517 - 06/12/13 06:45 PM

Quote:

Perhaps someone could suggest another to take it's place in the table?




I nominate STT 344. It is located in HER (near the border with Draco) and is currently viewable for many of us.

This binary has had 27 observations with a 2009 measurement being the most recent. Here are more stats:

mag1=6.5
mag2=10.3
delta mag = 3.8 (not 4 but pretty close)
sep=2.3"

Also, here is an image of this double by Florent Losse--so at least we know the secondary is there to be seen:

http://www.astrosurf.com/hfosaf/ids/stt344.jpg


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Re: Ever observed COU1900? new [Re: WRAK]
      #5917539 - 06/12/13 07:04 PM

Quote:

It seems that COU1900 is dubious but the data for BU1074 is as far as I can see very solid - so the double negative report from Mark makes me cautious. A positive on BU1074 and a negative on COU1900 would have been more convincing.





Considering how easy it was for me to view STT 344 with my 15" reflector and how similar this is to both BU1074 and COU1900, I am really surprised I cannot detect the secondary for BU 1074. I imaged STT 344; if I get a night of no wind, I will also try to image BU 1074 for more data to consider.

There exists the small possibility that the sky is not dark enough during the narrow window of opportunity I have to observse BU 1074 (close to after twilight) before it becomes occluded by my house. Also, I dont like looking at objects above my roof because of heat waves.

All that being said, last night was one of those classic hazy, still nights where the seeing was excellent and high powers gave crisp images (without the shaking due to wind). To the best of my ability all I detected was maybe a very faint secondary quite close to primary of a similar orange/red color---it at least appeared to have the correct position angle. What I saw was at best separated by 1 arcsecond.

I will keep looking.


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Re: Ever observed COU1900? new [Re: Nucleophile]
      #5917729 - 06/12/13 09:07 PM

Mark, I'm curious about the nature of this "artifact" that gave you a false positive in observing COU 1900. And whether it might occur in other angles than around PA 300.

I've come across other reports of this happening, including a report of seeing the companion of Procyon (an extraordinarily difficult object) with a 9-inch telescope - the observer used a filter that gave internal reflection, producing a dim reproduction of the primary star so it appeared to have a companion. Moving the primary around the field changed the position of the reflection.

Regarding BU 1074, I don't think there's any reason to doubt its existence as a double. It's rather a pity there are no measures after 1923 recorded, but the five measures obtasined suggest a pair virtually unchanging (or changing very slowly) in that period, as Aitken had a measure of 2.5" in 1899, the same as 1923, though a little wider than Burnham's discovery number. The one doubtful matter with BU 1074 is the magnitude of the secondary star, for which there appears to be no recent high-accuracy photometry; so the mag 11.2 might be old eye estimates.

In terms of change in separation, the Hipparcos parallax for the primary star suggests a large distance (slightly over 500 light years) so this is a system on a large scale, which can't be expected to change quickly. Hipparcos/Tycho did not pick up the secondary star, but that's not unusual around mag 11 and dimmer.

There are a couple of positive sightings of BU 1074 as a double in this thread, in addition to the old observations by Burnham and Aitken, so I don't think there's any good reason to doubt its existence as a double. The difficulty of seeing the companion, sometimes even with a 15-inch telescope, might be informative about the vagaries of seeing very uneven and quite close pairs. In particular, local seeing conditions, telescope thermals, and sometimes other factors can make such companions obscure or invisible.


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Re: Ever observed COU1900? new [Re: fred1871]
      #5917754 - 06/12/13 09:21 PM

Quote:


There are a couple of positive sightings of BU 1074 as a double in this thread, in addition to the old observations by Burnham and Aitken, so I don't think there's any good reason to doubt its existence as a double. The difficulty of seeing the companion, sometimes even with a 15-inch telescope, might be informative about the vagaries of seeing very uneven and quite close pairs. In particular, local seeing conditions, telescope thermals, and sometimes other factors can make such companions obscure or invisible.




Yes, and it also might be I was so tired the other night due to lack of sleep night after night I looked at the wrong star!
I dont know that this happened but I am thinking it may have.


One thing I know--it was a no go with the 8 inch the first time around---I had never hopped to that area so I am always careful to confirm the eyepiece view matches the cartes du ciel reflector view for that FOV before I star observing--that is why I am certain I had not seen it with that scope. But the other night I was hurrying and hopping based on memory of the prior hop---problem is there is another orange star about mag 6 in the vicinity and I may have just stopped there.

Naturally, there are clouds tonight. I am encouraged by the others positives to keep looking at BU1074. The negative for COU is firm though---that is a star hop ingrained into my head and no question I could not see a companion with the 15 inch.

The artefact appears in the same place each time and most of the time I am looking in the same area of the sky so I dont think it interfered with other observations---but it is something to be aware of---I am pretty happy this mass produced Orion mirror is as good as it is--and has travelled so well all these years. Someday a Zambuto will supplant it though.


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Re: Ever observed COU1900? new [Re: WRAK]
      #5917952 - 06/12/13 11:06 PM

Wilfried, that's a useful list of doubles to try for comparison. One of them (in Cepheus) is out of my sky always, but the other three are possible, and I've found I already have observing notes for two of them.

HDO 255 in Apus (16 40.8, -72 18) I looked at way back in 1996 with a C14 on a night of about 7/10 seeing. My notes: very close faint companion suspected 110x, glimpsed in steadier moments 160x, clear at 240x. I can try it again, with smaller telescopes (140mm, 235mm) when I get some clear sky.

FIN 198 in Musca (12 22.3, -73 30) I observed a couple of years ago with my current 140mm refractor; the air steadiness was not great that night, but I saw the companion flickering into view at 230x after hints of it at 160x. I'll try this one again as well.

SEE 291 in Scorpius - not observed yet; I'll put it on my list to do soon.

A bonus pair - A 524 in Monoceros (07 14.2, -03 54), I looked at 2 months ago - mags 6.14 and 10.17, separation 2.7" in PA 152 1991 (spec M1). I used the 140mm refractor, companion seen at 230x, steady in the best moments - seeing 7/10, best moments 8/10. That's a delta-m of 4.0, and a separation slightly larger, with the data suggesting a pair that's not changing much (1903-1991) though perhaps a tiny bit closer now, though the measures are within probable errors of each other (2.9" and 2.7" - perhaps 2.8" both times).


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Re: Ever observed COU1900? new [Re: fred1871]
      #5918181 - 06/13/13 03:28 AM

Yesterday I had the for me rare experience of a clear if somewhat bright sky - SQM showed around +17mag for the sky background and NEML was ~2.5mag. Seeing with 140mm and Polaris was ~6-7 Pickering but got worse due to a rather quick drop in temperature resulting in air turbulences.
Tried COU1900 again with my 140mm refractor (Bill assumed 4" aperture sufficient for this one but this seems a bit on the optimistic side to me. My RoT model suggests 138mm aperture for a fair 50% chance for a split and in this aperture range I trust my model meanwhile fully) but COU1900 is with ~35 altitude meanwhile already a bit low in the sky for me so I had anyway not a real chance regardless if wrong data or not. I then tried again BU1074 with negative result - my model here suggests 164mm and the companion is with +11.2mag already rather close to my NEML reduced TML of about +11.8mag or may be even a bit less.
A524 sounds good, proposed aperture 130mm refractor. Separation 2.7" may be already a bit too large to fill in the required place in Sissy's matrix.
Detto FIN198, proposed aperture 150mm refractor. Seems to look fine to fill in.
STT344 seems also quite interesting (proposed aperture 141mm refractor) but is in my opinion already a bit away in terms of separation and delta-m - but for me certainly an object of interest to check the validity of my RoT model.
I can suggest these candidates to Sissy (will may be look again for somewhat brighter candidates if a wider variation in sep (2.3-2.7") and delt_m (+3.8-4.2mag) is accepted.
But this is certainly the decision of Sissy Haas and as there are still several empty places in her matrix may be this slot can also remain empty.
I for my part have to quit on COU1900 even with larger apertures (still struggling to come to terms with my C9.25) as this one gets already too low in the sky for me for resolving even under else very good conditions.
Wilfried


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Re: Ever observed COU1900? new [Re: fred1871]
      #5918297 - 06/13/13 07:42 AM

Quote:

SEE 291 in Scorpius - not observed yet; I'll put it on my list to do soon.




I should be able to tackle this one as well soon enough.


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Re: Ever observed COU1900? new [Re: Nucleophile]
      #5918373 - 06/13/13 08:59 AM

Did not find any brighter doubles with the required combination of separation and delta_m.
Found another one with similar parameters like COU1900:
KU1 WDS16431+7731 2.6" +6.06/10.2mag in UMi with 19 observations according to WDS.
Wilfried


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Re: Ever observed COU1900? new [Re: WRAK]
      #5918893 - 06/13/13 02:18 PM

I've been back to Cou 1900 a few more times, Wilfried, and still am not quite satisfied I saw the secondary. I thought I had it one night in a six inch f/10 refractor, but I lost it quickly and never did get another good glimpse of it. Altogether I believe I've got about three hours of time invested in trying to catch the secondary.

It's too low in the sky for me now, also, so it'll have to wait until it rotates into view in the eastern sky later this year.

I'm of the opinion the secondary is really there, but it would be great if someone could come up with a photo of it in order to confirm it. This one has to be one of the toughest doubles I've come across.


John


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Re: Ever observed COU1900? new [Re: 7331Peg]
      #5919080 - 06/13/13 04:16 PM

Quote:


I'm of the opinion the secondary is really there, but it would be great if someone could come up with a photo of it in order to confirm it.




That is my plan when conditions cooperate.


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Re: Ever observed COU1900? new [Re: Nucleophile]
      #5920014 - 06/14/13 05:01 AM

Mark and John, thanks for putting this much effort into attempts for resolving COU1900, interesting topic anyway.
I hope we come any conclusive result here. To some degree I suspect that while COU1900 may exist the magnitude of the companion is muche fainter than +10mag - the number suggests only an estimation and not a precise measurement and as both observations were done with huge refractors the "real" magnitude of the companion might be so faint that we don't have a real chance with amateur scopes.
I hope this assumption is wrong.
Wilfried


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Bill Boublitz
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Re: Ever observed COU1900? new [Re: WRAK]
      #5922308 - 06/15/13 01:36 PM

Finally had an hour and twenty minutes to spend on Cou 1900 with 178 mm last night.

NELM 5.0, seeing; very good with calm lasting 10 seconds or more. Moon; day 6, lunation 1119, in Leo.

At x44, red "fringes" were noticed in PA 310, evidence of some type of refracting phenomenon. Examined x200, x300, x600 and x685... (higher than I typically employ). Primary blue-white, typical for type A2V. Observed some evidence of a possible deeper blue companion, in PA 310, (close to the 304 listed position). In terms of brightness, the appearance would be consistent with what would be expected on a pair with this magnitude difference. One positive thing I can say; whatever I was seeing; it never changed position. Whatever I was seeing also appeared 1.0" or less away from the primary. At no time was there any evidence of anything at 2.4" separation. An additional oddity; slight de-focusing revealed two "knots" in the diffraction ring 180 apart. One at PA 310, the other at PA 170. Typically, with a single point source, de-focusing simply shrinks the diameter of the Airy disk and throws more light into the diffraction ring equally, in all directions. Knots usually suggest the presence of multiple objects. At no time did I observe elongation in the primary itself.

That's about as honest as I can state it. While there might be some evidence for a multiple object, nothing was resolved. Yet, I wouldn't dismiss it as singular because it didn't appear/behave like a single point source of light. Cou 1900 demands greater aperture and hopefully some unbiased electronic means of documenting what is actually there.

Ironically, as I began writing this, the two week update came in from Sissy. It includes a positive resolution report on Cou 1900 using 550 mm. She made known some reservations, but instructed me to log it into the database for now. I don't think she's received my (somewhat ambiguous) report yet. Cheers! ~ Bill


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Re: Ever observed COU1900? new [Re: Bill Boublitz]
      #5922475 - 06/15/13 03:48 PM

Thanks for the report, Bill.

I am hoping to get some clearing tonight to collect and report more data on this one (and others). My very first impressions of this with the 15" were also that there was duplicity hinted at---but higher powers showed nothing.

Sure hope I can generate a pic before the moon conspires against me.


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Re: Ever observed COU1900? new [Re: Bill Boublitz]
      #5922477 - 06/15/13 03:51 PM

Quote:

An additional oddity; slight de-focusing revealed two "knots" in the diffraction ring 180 apart. One at PA 310, the other at PA 170. Typically, with a single point source, de-focusing simply shrinks the diameter of the Airy disk and throws more light into the diffraction ring equally, in all directions. Knots usually suggest the presence of multiple objects. At no time did I observe elongation in the primary itself.




I like this--will also try this once I am able to view the object again. (waiting, waiting, ...sigh)


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fred1871
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Re: Ever observed COU1900? new [Re: Bill Boublitz]
      #5922885 - 06/15/13 09:35 PM

Interesting report, Bill. Pretty certainly it can't be regarded as a positive sighting of the double. There's no reason to think the separation has suddenly dropped from 2.4" to 1" or less.

Your description of 'red "fringes"' and other details (bilateral knots in the diffraction ring) makes me wonder if there are optical issues of some kind with the telescope. That what you were seeing "never changed position" would fit for a telescope issue rather than a seeing conditions issue.

You mention "knots" in the diffraction ring 180 deg apart, but the PAs you give are 140 apart. Assuming one at 310, 180 offset gives PA 130, not PA 170. Think I'm asking for clarification

Good to hear someone with 550mm has tried it. Any details possible on what they reported seeing, given Sissy's "reservations" about it?

Incidentally - my guess in a previous note re Couteau finding COU 1900 with the Nice Observatory 30-inch refractor was wrong (based on late date for his discovery program); Wilfried has made available the full data list from WDS as a download, and it was the Nice 20-inch refractor Couteau used - about 510mm aperture.

The full data list also shows no result from Hipparcos (secondary too faint?) and no result from McAlister with speckle interferometry - delta-m too large is the likely cause, which is also consistent with a secondary fainter than the listed 10.0mag. The 2010 measure was, like McAlister, with a very large telescope, but not using speckle - adaptive optics in this case.


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Bill Boublitz
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Re: Ever observed COU1900? new [Re: fred1871]
      #5923246 - 06/16/13 04:59 AM

Thanks, Fred.

It shouldn't be regarded as a positive sighting; it wasn't.

There are most certainly "optical issues" with my telescope. A telescope is little more than a set of "optical issues."

PA clarification: opposite. Very sorry about the math. It was 4 am local. PA 130 accepted, My original estimate was only approximate. It may have been 309... that would make it, what (?) 129 degrees. Just for the record, of course.

Yes, good to hear about the 550 mm observation. No details available. You can always e-mail Sissy directly with your concerns.

Agreed on no result from Hipparcos, McAlister, etc. Often wondered why we're chasing this object in the first place. For the fun of it, I suppose.

Hope you get a look.


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Re: Ever observed COU1900? new [Re: Bill Boublitz]
      #5923273 - 06/16/13 06:04 AM

Quote:

... Often wondered why we're chasing this object in the first place. For the fun of it, I suppose...



"Chasing" is already the answer - it is a difficult object and therefore an interesting challenge. And even negative results from reliable amateur observers are while of no value for the Haas project certainly of interest for the maintenance of the WDS catalogue - enough errors to weed out.
Wilfried


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Re: Ever observed COU1900? new [Re: Bill Boublitz]
      #5924759 - 06/17/13 01:25 AM

My comments about no data from Hipparcos and McAlister were meant as an indication that this suggests a large delta-m (McAlister); fainter companion (Hipparcos); in other words, it's likely the companion is fainter than magnitude 10.0 as listed. Perhaps mag 11.0 or even fainter. It was simply the application of logic to data to give a probable result (probable, not certain, because there are assumptions, though I'd suggest reasonable ones, re the data).

On the suggestion that "A telescope is little more than a set of "optical issues."" - well, yes, but that tells us nothing. Your description of the red fringes and knots in the diffraction ring suggested a possibility of the kinds of "optical issues" that might give rise to spurious image effects. You'll notice, earlier in this thread, that Mark (nucleophile) ran into exactly this ype of problem with his 8-inch telescope, and consequently withdrew some observations that he therefore came to see as needing "retraction" because the telescope produced an "artifact" that simulated a star.

I've seen this happen with various telescopes, including some with good optics when they were out of adjustment, or had some other issue. It's usually fixable by adjustment or minor modification. So, my thought was, that perhaps your scope had an issue of adjustment or collimation or ???
One scope I owned used to develop astigmatism on cold nights because of pinching of an optical element as a cell contracted; adjustment solved that. I've also seen a cell pinch optics in a way that produced spurious star effects - such as bilateral brighter spots in the diffraction ring, similar to what you've noted. Hence my wondering about "optical issues".

Re the 550mm observation - I was merely wondering if Sissy had said why she had "some reservations" (your words).


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Bill Boublitz
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Re: Ever observed COU1900? new [Re: fred1871]
      #5925687 - 06/17/13 02:43 PM

From a technical point of view, I look at it this way;

The theoretical Dawes for 178 mm is 0.65". The best human eyesight typically resolves details as fine as 1 arc-minute apart. Therefore, 60 arc-seconds/0.65 arc-seconds = x92.3 (!) Theoretically speaking, (assuming good calibration), at x92.3, the 178 mm is already revealing all it is capable of resolving. The rest is eye and air.

In practice, for my eyes, x200 reveals 90% of what scope is able to resolve. x300 is often useful, but here the atmosphere begins to affect the image to a higher degree. On rare occasion, I've found x400 profitable to clarify what I've already seen at x300. At x400, the images are never that good. I don't mean distorted, just not crisp. So I've concentrated my time on learning to see more at lower magnifications. I've never had anything "pop out" at x400. If I first see it at that power, backing down to x300 always reveals it was there all along.

From what I gather, 100x per inch is often profitable with refractors. Indeed my first split of Antares with 4" was achieved at x400.

I would not expect any kind of text book image from the 7" Mak at x600-x685. I'm pushing it well beyond it's design limits. While it may hold up on a test bench, in the field (and down here near sea level), the atmosphere will never allow it.

Not to preclude the possibility, but at this point I'm not seeing any evidence of optical issues with this scope. "The red fringing" was only observed at low power (x44). The target was fairly high and the atmosphere moisture laden. Experience writes it off to atmospheric refraction. x200-x300 the image was clean, crisp, clear - no artifacts or distortions; no companion. Artifacts/distortions only appeared at x600/x685. My claim; there may be some evidence of duplicity.... That leaves a lot open.

Another reason why I would not yet begin to suspect my scope; the closet pair on the Haas table is 0.7". I have not yet failed to see anything on the list with more than x200-x300. The only pair that requires more careful revue is our beloved Gamma Equ...

As for the 550 mm log; she "didn't think it would hold up, but enter it for the time being." I act in a supporting role; receiving a set of apertures and numbers to enter and have no privilege to reports. (Thankfully.)

BTW, after hopefully completing the table early this summer, I will be taking the 178 mm in for routine servicing (every three years). If it's totally out of whack, I'll go back and do the table again... next year.

Okay, that's enough out of me....


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WRAK
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Re: Ever observed COU1900? new [Re: Bill Boublitz]
      #5939767 - 06/25/13 01:10 PM

I contacted Brian Mason again regarding COU1900 with the impression that the DeRosa confirmation of COU1900 is probably in error. Brian answered with the for me new information that DeRosa only measured delta-m with 3.08 in the infrared range and that the visual delta-m might be significantly higher or lower than. This answer is for me a bit disappointing because what is then the base for the current WDS entry +6/10mag? And I dislike magnitude data in the infrared range anyway because in my opinion magnitudes are a strictly visual concept.
Wilfried


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7331Peg
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Re: Ever observed COU1900? new [Re: WRAK]
      #5939921 - 06/25/13 02:43 PM

Wilfried,

Any ideas as to what's involved in getting a photometric value of the secondary's magnitude that is equivalent to the visual value? I understand the magnitudes of variable stars are determined that by way by some amateur astronomers, so it doesn't sound like it's a matter of relying on a large professional observatory to get the data. Of course you have to detect the seondary first, which has been the issue from the start.


John


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fred1871
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Re: Ever observed COU1900? new [Re: WRAK]
      #5940436 - 06/25/13 08:34 PM

Wilfried, that's exactly what I was (rather laboriously) pointing out (though I see now it was in another thread). IR delta-m numbers don't tell you what visual delta-m numbers will be. And there's no straightforward translation.

Unfortunately, my comments about this matter (IR versus V magnitudes) is in the thread about "Observations/Images..." towards the end; where I spelled out the issues (23 June 2013).

I'll post a summary version of my comments there to this thread, today. Keeps things tidier and easier to find.

Regarding John's (7331Peg) query, it's a matter of doing photometry in V-band rather than an IR region; that should be possible without a giant telescope given the separation of the components, allowing isolation of the secondary for brightness readings.


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fred1871
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Re: Ever observed COU1900? new [Re: fred1871]
      #5940476 - 06/25/13 09:02 PM

In another thread, recently ("Observations/Images...") I wrote some notes on the photometry of COU 1900 following some thoughts by John (7331Peg). The CN date for this is 23 June 2013.

Here's a summary, with lengthy quotations, to get these ideas into the right thread.

The de Rosa paper that provides recent photometry for COU 1900 has the problem that the photometry was done in infra-red, not visual wavelengths. This happens when measures of doubles are made in the IR, as they often are these days with large telescopes. It can lead to confusion.

" In the datarequest key notes [from WDS], I see "More recent additions to the delta-m catalog include filter information (typically, central wavelength & FWHM)..."
That suggests the "2200" listed is the wavelength for the 2010 photometric measure in nanometres. The delta-m catalog supports this.

2200nm is K-band, well into the IR, where a lot of the separation/PA measures are made these days. Therefore, the mag 10.0 estimate for the companion could be a corrected magnitude figure based on the companion's supposed spectral type, resulting in an estimated colour-index, in changing from 2200nm to V-band (standard is ~550nm). No spectral type is given for the companion in the data file ... so what basis was used? We're left wondering.

The WDS summary line includes no code, suggesting the magnitude is visual.

Therefore, the assigned magnitude (10.0) needs some kind of explanation as to how it was derived."

John then queried further:
I dug out the 2011 DeRosa paper (here) which only seems to muddy the waters more.

On page three is a table which includes a magnitude estimate of 5.53 for the primary of Cou 1900 -- it's listed there by its HIP number, 51200, and shows a K filter was used, which is referred to later in the paper as K'.

On page seven you'll find a table of data for the secondaries in the survey (Cou 1900 is shown as 51200 B). The separation (2.41") and the position angle (304.1 degrees) are listed in the second and third columns. The next column has the heading "Magnitude Difference" and has a value of 3.08 entered. I wonder if that is supposed to mean 3.08 magnitudes less than the primary? That would result in a magnitude estimate of 8.61 if that's the case. Again, a filter is shown, H2.

Apart from the filters, Fred, I don't see any reference to wavelength bands after skimming through the paper a couple of times.


To which I replied:

"No, it's straightforward in the sense that it doesn't change what I've said. The table on page 3 of that paper indicates the wavelength band for the magnitudes measured - K in this case, as before the IR band centred on ~2200nm.

The delta-m listed (3.08) I'd expect to be in the same band, and therefore indicates a brightness difference in the K band (IR). How that relates to brightness difference in the V-band (visual, ~550nm) is the issue - that's what I commented on in modest detail, suggesting the logic of what we want to know requires some method of determining the colour-index, to determine the (usually quite different) delta-m in V compared to K. As I haven't yet seen a spectral type for the companion, even a guess on likely colour-index correction isn't possible (averaged differences for the class, vs individually measured).

The primary star is main sequence (MK class V) and a 'Sirian' star, spectrum A2. That tells us nothing about the companion.

So - spectrum information for the fainter star would allow an estimate of possible V-magnitude delta-m, but much more useful would be V-band photometry of the fainter star, giving a direct measure."

SUMMARY: the IR data don't give us anything useful for visual observers, as Brian Mason has indirectly said : to quote Wilfried, passing on what Brian said:
Brian answered with the for me new information that DeRosa only measured delta-m with 3.08 in the infrared range and that the visual delta-m might be significantly higher or lower than.


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WRAK
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Estimating visual magnitude new [Re: 7331Peg]
      #5940912 - 06/26/13 05:11 AM Attachment (14 downloads)

Quote:

... Any ideas as to what's involved in getting a photometric value of the secondary's magnitude that is equivalent to the visual value? ...




John, sorry, have to quit here - no idea, but would be highly interested in a for an amateur feasable solution myself.

If the magnitude of a companion is in question I usually have a look at the APASS page of the AAVSO website (http://www.aavso.org/apass) if there are measurements at the given position - here are also visual magnitudes listed.
If this fails I use the following methods for crude estimations:
- For close doubles comparing the brightness of the comapnion with the first diffraction ring and then compare this impression with the data from a table from Chris Lords paper on Resolving unequal binaries giving an indication of delta-m depending on the size of CO
- For wide pairs I use an iris diaphragm to get to the smallest possible aperture resolving the companion. Given TML for given NEML is then a quite good indication for the visual magnitude of the companion
- For pairs in between I use sometimes my pA calculator in reverse mode if I know the limit aperture for this double - I simply change the magnitude value of the secondary in steps to get the equivalent pA. With the known standard deviation I can even calculate kind of range for a 95% probability range. While this "method" may be of some value for smaller apertures things get rather unreliable with greater apertures.

BTW - for COU1900 I would get a delta-m of ~7 if we take Mark's observation with 381mm aperture as limit observation.
Wilfried


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Nucleophile
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Re: Estimating visual magnitude new [Re: WRAK]
      #5941037 - 06/26/13 08:34 AM

Quote:

BTW - for COU1900 I would get a delta-m of ~7 if we take Mark's observation with 381mm aperture as limit observation.
Wilfried




It would be instructive if someone with an 11 or 12 inch instrument could take a crack at it and report their results here.

I saw the companion of COU 1900 again last night. But here is the fun part: the roof of my house partially blocked my view of the part of the sky containing the binary causing the light from the primary to dim somewhat--but the reduced glare of the primary aided in the identification of the secondary--I saw it immediately at 398x. Of course it helped that I have seen it once already and I know how to look for companion.


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Nucleophile
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Re: Estimating visual magnitude new [Re: Nucleophile]
      #5941100 - 06/26/13 09:22 AM

Quote:

It would be instructive if someone with an 11 or 12 inch instrument could take a crack at it and report their results here.





I estimate the roof blocked about a third of the aperture when I made this observation.

Did I inadvertently "mask" my aperture to an instrument of this size last night?


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7331Peg
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Re: Estimating visual magnitude new [Re: WRAK]
      #5941606 - 06/26/13 03:15 PM

A Delta-m of 7 seems like it may be a bit high -- I'm still leaning toward a magnitude of 11 for the secondary, mainly because I think I had a glimpse of it in my six inch refractor. I can't imagine that happening if there was seven magnitudes of difference.

But -- as I said -- I think I saw it. I'm still not convinced enough to call it confirmed, and it'll have to wait until later in the year now. So it's only supposition at this point.

It's good to know Mark has seen the secondary twice, since that eliminates any question of whether it's there or not. The observation with the roof blocking part of the aperture is definitely intriguing.

P.S. -- Thanks for that APASS link. I've been looking for something like that.


John


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Nucleophile
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Re: Estimating visual magnitude new [Re: 7331Peg]
      #5941650 - 06/26/13 03:50 PM

by my count, I have seen it at least 4 times with the 15 inch;
11ish sounds about right to me for secondary magnitude
I'm eager to take more cracks at it with the 8 inch.

Edited by Nucleophile (06/26/13 03:52 PM)


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WRAK
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Reged: 02/18/12

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Re: Estimating visual magnitude new [Re: Nucleophile]
      #5941849 - 06/26/13 06:04 PM

Quote:

...
I estimate the roof blocked about a third of the aperture when I made this observation.

Did I inadvertently "mask" my aperture to an instrument of this size last night?




Would call this a peripheral obstruction.
Would may be be of interest to make an aperture mask for your 15" Newton with for example 300mm. Even then your CO would still be rather small with ~0.25.
Wilfried


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Nucleophile
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Re: Ever observed COU1900? new [Re: WRAK]
      #5947389 - 06/30/13 12:22 AM

Can I see the companion of COU 1900? Yes, in fact I cant help but see it with my 15 inch reflector now.

The real questions for me is can I see it with another instrument. I used an on axis mask to stop down the 15 to an 11 inch instrument and strongly suspected the companion at 345x--but alas, it was not very dark then and there was some partial occlusion of the aperture by my roof--but it was a promising result at any rate.

I'll be point more than a few instrument at this one later in the year/next year once it comes back into favorable view again. So, its "bye for now" COU 1900--please dont change too much!


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WRAK
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Reged: 02/18/12

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Re: Ever observed COU1900? new [Re: Nucleophile]
      #5947491 - 06/30/13 03:17 AM

Mark, please send your observation report to Sissy Haas (has103@comcast.net) as she has still only one report on COU1900 with 550mm.
I too have to quit now on COU1900 as it is already too low in the sky - but it will come into my field of view again in April next year near zenith and I will then try again. By then I should already have the 8" Royce Dall-Kirkham and I have some expectations regarding the performance of this instrument.
Wilfried


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Nucleophile
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Re: Ever observed COU1900? new [Re: WRAK]
      #5947641 - 06/30/13 07:56 AM

will do

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Bill Boublitz
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Reged: 05/04/13

Re: Ever observed COU1900? new [Re: Nucleophile]
      #5970443 - 07/14/13 02:07 PM

Interesting note: 07-14-13 a resolution of COU 1900 using 152 mm was reported and filed in the Haas database. No idea whom or any further info, but a number of resolutions were filed this week with this aperture.

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Nucleophile
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Re: Ever observed COU1900? new [Re: Bill Boublitz]
      #5970548 - 07/14/13 03:06 PM

that is indeed interesting; am glad some others are still adding data.

I may redo the list with my 15" stopped down to an unobstructed 6" just to get more data points in there.


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WRAK
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Reged: 02/18/12

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Resolution of COU 1900 with 152 mm aperture new [Re: Bill Boublitz]
      #5971689 - 07/15/13 05:07 AM

In the very beginning of this thread also Roberto reported a "suspected" resolution of COU1900 with an 6" refractor showing a hint of a reddish companion. COU1900 career as curious object with this new report extended.
Wilfried


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WRAK
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Reged: 02/18/12

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Re: Resolution of COU 1900 with 152 mm aperture new [Re: WRAK]
      #5990704 - 07/26/13 03:21 AM

Mark - just curious: Why did you not send your COU1900 observation report to Sissy?
Wilfried


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