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Ever observed COU1900?

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#26 7331Peg

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Posted 15 May 2013 - 11:26 PM

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.


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#27 WRAK

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Posted 16 May 2013 - 01:54 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

#28 R Botero

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Posted 16 May 2013 - 07:59 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?

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#29 7331Peg

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Posted 16 May 2013 - 01:49 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.


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#30 WRAK

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Posted 16 May 2013 - 02:19 PM

...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

#31 WRAK

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Posted 29 May 2013 - 02:05 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

#32 fred1871

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Posted 29 May 2013 - 08:43 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.

#33 Nucleophile

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Posted 07 June 2013 - 05:33 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 :) )

#34 Nucleophile

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Posted 07 June 2013 - 05:42 PM

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

#35 Nucleophile

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Posted 07 June 2013 - 05:46 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! :)

#36 Bill Boublitz

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Posted 07 June 2013 - 10:25 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!

#37 WRAK

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Posted 08 June 2013 - 09:43 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

#38 Nucleophile

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Posted 08 June 2013 - 05:11 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).

#39 Nucleophile

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Posted 12 June 2013 - 11:52 AM

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.

#40 Bill Boublitz

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Posted 12 June 2013 - 02:41 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?

#41 WRAK

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Posted 12 June 2013 - 03:37 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

#42 Nucleophile

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Posted 12 June 2013 - 05:45 PM

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.../ids/stt344.jpg

#43 Nucleophile

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Posted 12 June 2013 - 06:04 PM

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.

#44 fred1871

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Posted 12 June 2013 - 08:07 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.

#45 Nucleophile

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Posted 12 June 2013 - 08:21 PM

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.

#46 fred1871

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Posted 12 June 2013 - 10:06 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).

#47 WRAK

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Posted 13 June 2013 - 02:28 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

#48 Nucleophile

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Posted 13 June 2013 - 06:42 AM

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.

#49 WRAK

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Posted 13 June 2013 - 07:59 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

#50 7331Peg

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Posted 13 June 2013 - 01:18 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 :refractor:






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