The Calm After a Storm
Posted 13 October 2013 - 08:17 PM
First up was the interesting double Kui 97, but unfortunately it was first up. The seeing was not good at 5 or 6/10 Pickering. Some of that was failure to cool the scope to ambient, verified by a small plume that should dissipate in the relatively warm tropical air. The remainder of seeing was relatively unsteady air. After cooling I was hopeful seeing would improve to about 7/10.
I really did not know what to expect from Kui 97. I thought I chose it because it was an unequal pair with a fairly wide separation, however I failed to spot any widely separated unequal companion. The Airy disc was mostly blurry and the first ring was ill defined and washed out. Kui 97 rapidly bounced in the FOV over a couple arc seconds.
It was difficult and looked to be a bad night for doubles. It was not a great start. But, then again being 15 degrees N latitude placed Kui 97 over a neighbor's roof top across the street. Still fairly well placed, but I gotta wonder if the seeing was disrupted somewhat.
I tried hard and failed to spot a companion somewhere outside the first ring. I did get some impression of an elongated central disc, but quickly wrote that off as seeing effects. Turns out, that is what I should have been looking for - a 9th magnitude companion inside the first ring. I really want to try this one again as last night's observation was inconclusive.
A quick check on Deneb verified seeing was not all that great with some atmospheric dispersion, but collimation seemed very good and seeing seemed to be better. A quick swing toward Chi Aql to confirm a recent observation proved very difficult. Again, the image just was not steady enough.
After about an hour with Kui and a few minutes with Chi Aql, I swung over to Alpheratz to begin star hopping to STT 2AB, an interesting very close double. Checking seeing using Alpha Andromeda showed some nice steady views in this part of the sky. Kui 97 and Chi Aql were placed over neighbor's roof tops, but Alpheratz was creeping up the eastern sky toward the zenith. Seeing seemed much improved approaching 8/10. The evening was looking better, even though occasional high, thin clouds passed overhead. NELM was about mag 4.
I located and star hopped to STT 2AB, a very tight 0.4" separation of two 7th magnitude stars. I did not hold out much hope having been burnt by the seeing earlier, but it's first ring seemed pretty well defined. Actually, so did it's central disc. I was able to glimpse some elongation of it's central disc at 390x, but it was fairly difficult. So, I cranked the magnification up to 520x for a look see. If you could just magnify it enough, it would seem to be so much easier. Still, there it was, elongated very slightly just east of a north south line. I guessed about PA 160 rounded to as accurate as possible to the star's drift across the FOV and a 13.5 mag star at about PA 240.
(I just realized that nearby star might have been STT 2C, it at nearly the right PA - based on a quick estimate - and about the right separation. Stellarium lists the star at 13.5 mag while the catalog shows it to be mag 10.37. Truthfully, that was probably the C component and I didn't know there was one. It did appear a bit too easy for 13.5 magnitude, as well, so it may well have been much brighter at 10th mag.)
Given the recent look at Chi Aql, I had no idea what to expect with STT 2AB. Strangely, it seemed a wee bit easier than Chi Aql also near 0.4" arc. For Chi Aql, it was difficult to call any elongation at all, but STT 2AB appeared, sure enough and somewhat surprisingly so, to exhibit a tiny bit of elongation. It appears to be wider than Chi Aql. Either that or the seeing was just a tad better in the open eastern sky while Chi Aql was closer to a local roof top (two story apartment) making it a tad more difficult. (I am still becoming familiar with the local sky having just moved here.)
Dropping down to another tight double, and one easy enough to find, the next target was 36 And. It's listed near 0.66" arc, well below the advertised Dawes limit for a 150mm aperture. I star hopped to it's location and got my first look at it with 240x.
Immediately, the split seemed super easy exhibiting a prominent dark space. This was kind of shocking, because it looked like a pair of headlights in the dark - easily split with a dark space. Something did not seem right, it had to be wider than 0.66" arc. Either that, or having just come off the much more difficult STT 2AB made 36 And appear to be so much easier.
I tried to get a feel for where the companion was sitting relative to the first ring by extrapolating the ring around to and superimposed onto the companion. It wasn't easy to do, but it seemed to suggest the companion was closer to, if not on or just inside the first ring. One might think this would put the actual separation closer to 1" arc or more. One might expect to see a pinch in the rings, maybe. There may have been a slight pinch, but it appeared more or less elongated. It was very hard to tell and thus very hard to make an estimate of where it would lay on the primary's ring. So, not sure what to make of it's separation: close with a prominent dark space and an easy split. (Almost too easy for 0.66" arc and such a prominent dark space. Maybe not.)
I am not sure what to make of the cataloged separation of 36 And or it's very easy split. Something is amiss, or it just appeared to be easier compared to STT 2AB and Chi Aql. This is, of course, the case, but could it actually be at 0.66" arc and that easy in comparison? Or is it actually wider than advertised?
Last on the list was STF 133. Star hopping to it (using the finder) and the initial observation at 240x showed what appeared to be an initial success at splitting this one. It was almost too easy for an unequal pair. Something was not right.
I was looking for STF 133AB, and noticed two fainter stars due south. They seemed to be a bit too far for the B companion being 3" arc from the primary. Elation turned into a failure, so I cranked the magnification to 390x to see what I could see. At the time, I did not realize both 11th magnitude stars about 20" arc south of the primary were actually part of a multiple star system. But, it certainly did appear that way. It turns out, they are listed as STT 133C and D.
It turns out, splitting the two ~10.5 mag CD from each other at 5" was easy, too, as was splitting them from the primary. I could hold CD constant. However, B remained elusive at 3" arc separation and delta mag 2.65 (9.44 magnitude.)
Then it happened, I had one of those "yes" moments with a faint speck appearing just south of the primary's first ring. It was faint and very fleeting, I could not hold it for any length of time. I settled in for a long observe for this one determined to get it, it was not going to be easy. And it was not easy. Over the course of loosing track of time, and by the end of the session, I had acquired about a half dozen "yes" moments using averted vision and directing my gaze around the primary. None of them were easy or conclusive. So, the end of the night were simply a series of inconclusive, random, fleeting "yes" moments. I like to think it was the companion, but it was just too tough to make a call.
It was enjoyable and tonight looks to be clear, too. No storms headed this way, yet.
Posted 13 October 2013 - 10:54 PM
Data on 36 Andromedae - I don't know what your software's been smoking, but it hides the real data. 36 And is a binary, gd 2 orbit of 167.5 years, ephemeris suggests 1.1" at present. Last measure was 2011, 1.2" in PA 326. I guess that explains the resolution looking so good.
The orbit does bring the pair down to 0.66" at times, but it's been quite a while since then.... maybe your software is reminiscing about the old times?
Posted 13 October 2013 - 11:41 PM
I am glad you made the call on STT 2 - did you see any color difference between the merged discs? It looks like it could have appeared yellow and white paired. I'm glad you had success here and made interesting comparisons to Chi A.
The success in your last challenge was a happy ender to the previous objects issues.
I enjoyed the account - especially STT2. Well done.
The following is the WDS page diagrams however don't support the seperation exceeding .66".?
Posted 14 October 2013 - 12:01 AM
The pair is widening, and the 6th OC diagram shows that. Curiously, the diagram also places the last measure neatly on the calculated orbit line. Perhaps the last measure was at 1.15" and was rounded up to 1.2"?
Pete, I can't tell from the beginning of your note which double you're talking about.
Quote: That latter mentions 0.8" while WDS sais it was .66 in 2011. Which double are you referring to?
Posted 14 October 2013 - 12:08 AM
Pete, no color noticed on STT 2, I should pay more attention. I was just focused on confirming elongation.
I had planned some very close doubles and some widely separated unequal pairs. I mistook Kui 97 for BU 67 and expected it to be a wide pair. Gotta hit both of them again, tonight if possible.
I had no idea the seeing would be so iffy, it was the first clear night in a long time and it was not going to waste. Seeing did improve. I think the scope finally cooled closer to ambient over an hour or so and away from the roof tops seeing was better.
Posted 14 October 2013 - 01:08 AM
Rooftops? - great source of thermals, poor observing over them. I can see why some folk settle out of town with no nearby neighbours, as an aid to observing.
Posted 14 October 2013 - 04:13 AM
Yes, not to fault Stelledoppie, really, I love the site. But, there is something wrong with the orbit produced, apparently. Just have to be more guarded.
Posted 14 October 2013 - 06:20 AM
Posted 14 October 2013 - 09:40 AM
It's a curious one because it's a tight split. But, at 0.8" arc or a little wider, it should not have been a big deal. Maybe the delta mag of about 3 caused some problems.
Posted 14 October 2013 - 05:36 PM
Pete, I didn't see those diagrams the first time I looked at your note, or I'd have commented then.
The upper one is weird - two scaling versions (compare vertical and horizontal) and a set of dates that suggest a binary of only a few years period.
The lower diagram, copied from the 6th Orbit Catalog, has had the scale information removed - the original has scale marks across the bottom and down the left side. It's an easy task to copy the original as it is, rather than edited so that essential information is missing. It's obvious on the original that maximum separation (bottom of the ellipse) is well over 1.0", estimated ~1.3". And the orientation information (North, East....) is missing as well from the copy.
I've attached the full version of the file.
Posted 14 October 2013 - 05:57 PM
But, at 0.8" arc or a little wider, it should not have been a big deal. Maybe the delta mag of about 3 caused some problems.
Ummm,yes, a delta-m of about 3 might have an effect....
(Norme, are you indulging in irony? - it can get you into trouble, you know...)
Kui 97 has listed mags of 5.96 and 8.84, delta-m rounded as 2.9. That's the same as 42 Orionis - I expect we all remember that one. And 42 Ori is probably 1.0", a little wider than Kui 97, so 42 Ori should be easier. Yet 42 Ori is very very difficult with 140-180mm telescopes, as comments here agreed.
On the numbers, Kui 97 should be tougher. However, it might benefit from Rayleigh - the first dark interspace is at ~0.8" for a bit less than 7-inch aperture. For 42 Ori, the first dark interspace fits for 140mm (5.5-inches). And, I found being able to see 42 Ori double with that aperture was still extremely difficult, depending on very good seeing conditions and high power.
So, even for a scope where the companion of KUI 97 sits in the first dark interspace, it can be expected difficult.
Posted 14 October 2013 - 07:52 PM
Hmmm... looks as if Stelledoppie still has some problems with orbits. The quoted figure is not at all current. A check on the orbit suggests 0.66" fits for 1985 and 1949 (opposite sides of a fairly open orbit). The quoted PA there, 150d, fits for 1949. Interesting.
Fred, I can't follow you. Where did you took the data? 1949? 1985?
This is circa 4-years orbiting star.
Data may change everyday, so I preferred to display daily separation in the table. I could choose to adopt Orbit6 standard, every Jan 1st of each year, but you'll see repetions every 4 rows. Not so useful.
I don't see the graphs as different. They use different scales, shapes vary.
Are you talking about 36 And, right?
Posted 14 October 2013 - 08:04 PM
I was questioning how the delta M is affected inside the first ring. It's easy to understand difficulty being on the first ring, or any ring for that matter, but the lack of a ring inside the first one makes the difficulty curious. Maybe it's pure glare from the primary that causes this one to be so difficult? The split should be easy, especially at lessor delta M with a more equal close pair, but it's not easy at all. So, my question was sincere, how does delta mag affect a companion inside the first ring and why?
I still suspected some elongation, but was forced to write it off as totally uncertain because the central disc just wasn't steady enough. There was way too much error to make a call with even a small amount of confidence. It appears it might not be doable, anyway, given your analysis.
Yea, I remember 42 Ori well. It was very difficult. Very difficult. It resulted in a "lucky" guess to the PA based on a long observing session. There were spurious effects even in moderately good seeing, but the companion (I'm sure) betrayed itself over time with an occasional quick glimpse...that did resemble some spurious effects.
If memory serves, 42 Ori pretty much /appeared/ to sit on the first ring. I would think Kui 97 could be more like a Dawes split - benefit from Raleigh - less affected by the ring structure. Maybe it is not so.
Posted 14 October 2013 - 09:05 PM
A 3-4 year binary fits for Pete's upper diagram with the varied x- and y-axis scales. But that's not the double Struve discovered in 1830, for which we have the 6th OC orbit diagram. If the period was 3-4 years, the real separation would have to be very close in AU terms, and at ~125 ly (Hipparcos distance for 36 And) that would make for a very very close pair, that I'm sure would be always beyond 15-23cm telescopes.
Delta Equ, about twice as near to us (at ~60 ly) as 36 And, and with a 5.7 year period (not 3 or 4 years), has a maximum separation of about 0.33".
At the moment I can't find anything in the WDS or Notes thereto that mentions an Aa very close and short-period pair, additional to the STF pair (AB).
Has some other, short-period binary, come up in the data instead of 36 And AB?
Posted 14 October 2013 - 09:30 PM
Posted 14 October 2013 - 09:33 PM
Your question is a good one - the effect of primary glare on visibility of a secondary star in the first dark interspace, caught between brighter star and diffraction ring.
My initial feeling is that it has to be affected by glare issues - so optics that have little spread light effect will do better than those that allow light flare or glare to spread. There's always a little of this even with the best optics, but some do better than others. I've mentioned before that my ortho eyepieces do better in this than my T6 Naglers, used on the same telescope. And some telescopes' main optics will do better than others - better optical accuracy, better baffling, etc.
Another factor would be seeing. Diffraction rings can get rather patchy/smeary in some conditions, and that won't allow easy visibility (or sometimes any visibility) of faint-ish secondary stars, when light is being spread around, which can only reduce contrast, thereby reducing the benefit of the dark interspace. I'm inclined to think Pete's idea of rings moving away from secondary stars due to seeing is likely to help only when the secondary is not too faint; otherwise it's likely to be lost in the moving light patterns.
The magnitude difference of the stars (delta-m) has to matter. Smaller delta-m will help visibility; it's then harder for other factors to overwhelm the secondary. Thus far, looking at various unequal pairs, I'm hitting a limit around delta-m of 3 for secondary stars in the first dark interspace, with the 140mm refractor. I suspect the 235mm SCT does not do quite as well - optics a bit less good, large CO, more seeing-affected.
So I can't say what's the complete answer, but the above suggestions might be a start.
Posted 15 October 2013 - 02:35 AM
Muhahaha ha! Laughting, for not crying...
Fixed. Thank you.