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Some close pairs in Corona Borealis and Bootes

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#1 Adam Long

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Posted 24 June 2020 - 06:03 AM

It has been an exceptional spring in the British Isles, with record numbers of clear nights. This clear spell ended in early June with a few nights of exceptional seeing - the best I've experienced. These observations were mostly made then, in my 10" dob.

 

My normal practice is to mark up a few targets beforehand in CDSA, with sep and mags only so no knowledge of PA. I'm interested in observing motion so have been concentrating on improving my detection at small separations, but because CDSA is a few years old now I'm being caught out by the faster pairs, see below. I tend to 'warm up' with a few familiar pairs like Izar to assess seeing, then decide whether it's worth trying for the closest pairs.

 

OΣ 285 Boo - +7.7 / +8.6, 0.5", 76o

Super-close white pair, seen touching occasionally separating at 436x. PA estimated at 70o. Appear almost matched despite ΔM of 0.9, hard to tell which is the which. Noted sec 'probably following' which turned out to be correct. 89yr orbit, PA slowly decreasing.

 

OΣ 298 Boo - AB +7.2, +8.4, 1.2", 188o, C +7.7, 120", 328o

A neat triple, a bit like a miniature Alkalurops. Best view at 300x. AC sep 100x AB. PAs estimated at 210o and 320o. 55 yr orbit with steady increase in PA over the next decade.

 

γ CrB / Σ1967 - +4.0/ +5.6

This is where it gets interesting. CDSA has this at 0.6" (2015), and with the significant ΔM of 1.6 I was expecting a challenge. After a long look at 436x in good but not perfect seeing I was convinced of the airy disc appearing slightly smudged/ extended around PA 100o.

On checking Stelledoppie the following morning I was initially excited to see the current ρ/θ listed at 0.22"/ 105o. This would be my closest detection yet and, at 0.48 of the Dawes limit about as close as I can realistically hope to go. And at a significant ΔM too, with my sketch noting almost exactly what I'd expect to see and the PA a very close match.

But on looking at the orbit, doubts started to creep in. The 91yr grade 2 orbit has the pair closing rapidly - 0.22" for 2019 but 0.145" for 2020, and us now halfway through the year. I wrote 'not credible' below the sketch in my observing notebook, and renewed my reading on diffraction artefacts.

 

The following night was clear and viewing the 1/2 moon at 220x in the dusk it was clear the seeing was pretty special. As the skies darkened I slewed the scope to Izar and moved up to a 4mm Nirvana eyepiece giving 300x. Oh my! As I approached focus the rings of diffraction barely shimmered, and I was rewarded with an almost stationary view that finally justified the epithet 'Pulcherrima'.

 

ζ Boo / Σ1865 -  +4.5 / +4.6

CDSA has this pair as earning a showpiece *, and recommends them as a resolution test at 0.5". Stelledoppie also has the headline sep as 0.5",  but the 125 yr grade 2 orbit has it at 0.25 for 2020. But looking closely the list of predicted measures is all over the place and the plot appears to break down around periastron. This may be related to the eccentricity of 0.98. So who knows? Either way, in excellent seeing at 300x, 436x and even 600x (though a little low at 52o N) I couldn't see any sign of the secondary.

 

I returned to γ CrB. This time I saw no elongation of the airy disc. However, on reflection, I was now convinced there was nothing to see, whereas the first observation was very much with an open mind. The near perfect PA estimate was still nagging at me...

 

η CrB / Σ1937 -  +5.7 / +5.9

CDSA has this at 0.7", which should be properly split in my scope. But again, stellar motion over the five years since publication was enough to put it out of date. I observed the stars as yellow and the single airy disc like an elongated egg with no notching, sep estimated at ~0.4" and PA estimated at 300o. In the morning, stelledoppie gave figures of 0.36" and 280o. 41yr orbit which is now at it's closest, but will never exceed 1", so should be followable throughout in this scope.

 

ζ Her / Σ2084 -  +2.9 / +5.4, 1.36", 112o

If you aspire to observe stellar motion, this has to near the top of your list. A bright, easily found star with a mere 34 yr period that should be observable in medium apertures throughout. I saw a bright white primary with a nicely spaced orange secondary, a very pretty sight in good seeing. Will be above 1" for the next decade with PA steadily decreasing.

 

ξ Boo / Σ1888 -  +4.8 / +6.9, 5.3", 298o.

A pretty sight, close at 91x, well separated at 220x and perhaps best seen at 136x in this scope. I made the colours cream and yellow/ orange, PA estimated at 280o.

 

θ CrB / Cou 610 -  +4.3 / +6.3, 0.8", 199o

I approached this with trepidation as I knew the ΔM was getting large for a sub-arcseconder. At 300x I saw nothing. At 436x the pale blue comes appeared immediately, embedded in the diffraction of the cold white primary and forming a nice contrast. PA estimated at 200o. Once I knew where to look it was just visible at 300x. The nature .of this double is uncertain, but it was getting late and with the forecast for cloud for the foreseeable, I had a hard time pulling myself away from this tiny little jewel. Worth a look. What a great area of sky this is!

 

IMG_3678.jpg

 

While looking at θ CrB, it occurred to me that closing these stars to overlapping should still be just detectable, and would look a lot like my observation of γ CrB. I went back and added a question mark to my 'not credible'... 

 

I was reminded of this this morning as Augustus posted that he thought he'd split it last night in his 14.7". Be interested in others' thoughts and observations.


Edited by Adam Long, 24 June 2020 - 06:20 AM.

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#2 flt158

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Posted 24 June 2020 - 08:20 AM

Hello, Adam. 

 

I am so greatly pleased you have taken the time to being completely honest as to what doubles you could or could not split with your 10" Dobsonian. 

Some of these I have steered myself away from in recent years. 

As an owner of a William Optics 158 mm F/7 apochromatic refractor, I am capable of using magnifications up to 374X. 

But I rarely use my Radian 3 mm eyepiece. 

 

However I am delighted to state I have had great success with 2 of your doubles - albeit back in 2015. 

My scope successfully split STT 298 in Bootes at a rather charming 225X through a Nagler 5 mm. 

The separation was then 1.2". The PA was 298 degrees. 

I was completely bowled over by this beauty!

It even made into my top ten best observations for 2015. 

 

Zeta Herculis was also successfully split on 17th August 2015. 

But for some strange reason it needed 320X to split it - even though its separation was 1.2" also. 

My Nagler 3.5 mm did the job. 

The PA was 138 degrees at the time. 

Anyway it was all for the good!

 

Therefore I do very much thank you for bringing back some happy memories to me personally.  

You are always welcome here with any future observations. 

 

Clear skies to you, Adam. 

 

From a humble Irishman, Aubrey. 

 

P.S. I have never been to Sheffield, but I love the snooker on the BBC!!


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#3 Astroman007

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Posted 24 June 2020 - 08:46 AM

Those detailed descriptions! waytogo.gif

 

Well-written report, thank you for sharing.


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#4 nerich

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Posted 24 June 2020 - 10:54 AM

Adam, 

Terrific observations! Like Aubrey I admire your very objective approach and willingness to doubt yourself. Thanks for sharing these fine pairs and your detailed notes. 

 

 

From a humble Irishman, Aubrey. 

 

P.S. I have never been to Sheffield, but I love the snooker on the BBC!!


Another snooker fan here! And yeah, I definitely hope to make a pilgrimage to the Crucible Theatre one day. 


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#5 river-z

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Posted 24 June 2020 - 11:03 AM

Great report.  I'm going to have to give a few of these a close look.


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#6 Augustus

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Posted 24 June 2020 - 12:04 PM

Hi folks, Adam directed me over here. I split Gamma CrB a few nights ago with my 14.7" - the primary is blue with a lavender-colored secondary, seemed to be to be around half an arcsecond? 


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#7 mccarthymark

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Posted 24 June 2020 - 01:32 PM

Adam, these are excellent observations of neat stars, well done.  

 

I've made observations of several of them, for your reference:

 

STT 298:

July 2017: 12.5-inch 553x: Close equal pair, ~2".

June 2019: 8-inch 205x: At zenith, but worth the effort to slew to.  The AB pair is near equal and split a little more than a hairline
 

STF 1967:

June 2019: 8-inch 667x: Definite mis-shape, oval to egg

May 2020: 20-inch; 1067x: Disk is misshapen, but not easy to tell an orientation. 

 

STF 1937:

June 2020: 8-inch 667x: definite egg shape., each lobe a different magnitude, can tell it is not round at 205x, and detect elongation at 333x, but needed higher magnification to see well. 
 

STF 1888:

April 2020 20-inch; 333x: Richly colored yellow and orange stars, ~1 delta mag, ~5" separation, with several other stars in view. Very pretty.

 

STF 1865: 

April 2020: 20-inch ;1067x: First impression was moderately well notched overlapping disks (eg. not barely notched, but not strongly notched either). With more time observing & getting used to the image, and in moments of better seeing, the notch became more distinct. It would not separate in spite of moments of better seeing. I could also see the elongation, but only subtly notched due to the smaller scale, at 667x

 

STF 1937:

July 2017: 12.5-inch 553x: Overlapping / notched orange-yellow stars. Used apodising mask.

August 2018 12.5-inch 277x: Close orange pair, equal mag, snowman shape;

June 2020 8-inch 667x: 8" @ 333x, Suspect elongation. 8" 667x definite egg shape. 20" 667x: Can't get a good focus seeing doesn't support

Cou 610:

Aug 2018: 12.5-inch, 738x Tried pretty hard at 553x with apodizing screen, but dances too much. Used 6mm ortho with barlow, 738x, and at best moment it is olive shaped, but marginal. 

June 2018: Cou610 30-inch 915x Fractured and dancing in seeing. 915x, at full aperture and with 8-inch aperture mask, I see a slight out of roundness.

June 2019: 8-inch 667x Notched/snowman at best moments. B definitely fainter and almost blue. looks like an appendage. 20" seeing is too messy. 

June 2020: 8-inch 333x: I can only coax a misshape at all powers up to limits of seeing 667x.


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#8 Adam Long

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Posted 24 June 2020 - 02:27 PM

Thanks for the kind words folks. Of course I am a snooker fan too, but to my shame have not made it to the Crucible yet!

 

 

My scope successfully split STT 298 in Bootes at a rather charming 225X through a Nagler 5 mm.

The separation was then 1.2". The PA was 298 degrees.

I was completely bowled over by this beauty!

It even made into my top ten best observations for 2015.

Yes Aubrey, a cracker!

 

 

Zeta Herculis was also successfully split on 17th August 2015.
But for some strange reason it needed 320X to split it - even though its separation was 1.2" also.

Might be worth revisiting this as it is now a little wider and you should see a significant change in PA. A pretty sight too, though it needs a steady night.

 

 

I split Gamma CrB a few nights ago with my 14.7" - the primary is blue with a lavender-colored secondary, seemed to be to be around half an arcsecond?

Thanks Augustus, that's interesting. If you have chance, perhaps take another look and compare to the nearby doubles Eta CrB (similarly tight but closer in mag) and Theta CrB (wider at 0.8" but more uneven).

 

 

STF 1967:

June 2019: 8-inch 667x: Definite mis-shape, oval to egg

May 2020: 20-inch; 1067x: Disk is misshapen, but not easy to tell an orientation.

Thanks for all those Mark, that's just what I was hoping for - really interesting. Your observations of STF 1967 seem right in line with the ephemeris. Stelledoppie gives the Periastron as 1931.6 +/- 0.3 and the orbit as 91.2yr +/-0.4, so likely some time in 2022. The orbit plot below looks to have few observations in the crucial central periods, so I guess there is potential for it lagging a little but perhaps not as far as Augustus' observation would suggest. I'm still parking this in the maybe category for me!

 

wds15427+2618b.png

 

 

STF 1865:

April 2020: 20-inch ;1067x: First impression was moderately well notched overlapping disks (eg. not barely notched, but not strongly notched either)

Ok, that's interesting, and recent! Have you got a ballpark separation for that sort of notching in 20"?

 

 

STF 1937:

July 2017: 12.5-inch 553x: Overlapping / notched orange-yellow stars. Used apodising mask.

August 2018 12.5-inch 277x: Close orange pair, equal mag, snowman shape;

June 2020 8-inch 667x: 8" @ 333x, Suspect elongation. 8" 667x definite egg shape.

Yep, that seems exactly in line with mine. Thanks!

 

 

Cou 610:

Aug 2018: 12.5-inch, 738x Tried pretty hard at 553x with apodizing screen, but dances too much. Used 6mm ortho with barlow, 738x, and at best moment it is olive shaped, but marginal.

That seems much too tight, have you mixed it up with Cou 1610? Cou 610 is 0.8" so should be well split in your scopes.


Edited by Adam Long, 24 June 2020 - 02:37 PM.

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#9 mccarthymark

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Posted 24 June 2020 - 02:52 PM

STF 1865: for my 20-inch, theoretical notched / Sparrow criterion would be 0.214" -- which I've gotten on pairs of ~9-10th mag.  BUT in reality if pairs are brighter (as these are 4th mag) and the seeing is good but less than perfect, I would get a notching -- I don't have reason to doubt WDS class 2 orbit which puts these at 0.53"

 

Cou 610: No mix up.  I think this pair his highly aperture/seeing dependent and I don't think I've had good enough combination of both.  Too little aperture and not enough resolution given the delta mag, too much and the image is destroyed by seeing.  ~10-15 inch on a very good night of seeing seems about right?


Edited by mccarthymark, 24 June 2020 - 02:53 PM.

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#10 Adam Long

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Posted 24 June 2020 - 03:19 PM

STF 1865 - 0.214" sounds in the ballpark. The orbit on Stelledoppie was reducing steadily but turns to nonsense in the last few years, so 0.53 is surely wrong.

 

Ah, found the data direct from the orbit catalog - this is better:

 

14411+1344  STF1865AB        2      Sca2007f    

2016: 289.2   0.400   

2017: 287.6   0.365   

2018: 285.7   0.328   

2019: 283.3   0.289   

2020: 280.1   0.246

 

I will have another look at this, should be possible.

 

Cou 610 is tricky but well separated in good seeing in 10". It's one of the Haas project pairs  with splits recorded down to 127mm.


Edited by Adam Long, 24 June 2020 - 03:24 PM.

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#11 mccarthymark

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Posted 24 June 2020 - 03:27 PM

Oh I remember this one now too -- yes I think the header on Stelle Doppie 0.53" is incorrect; lower down on the webpage they have a different figure for 2020 0.248" -- which I think agrees with my notched observation; checking my log I rated seeing 8/10Capture.PNG


Edited by mccarthymark, 24 June 2020 - 03:27 PM.

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#12 Adam Long

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Posted 25 June 2020 - 04:37 AM

Just remembered this one is in Bob Argyle's recent Anthology too. Some good info, inc. a corrected orbit diagram (as on stelledoppie, N down, E right) and notes that 'the eccentricity is the highest known of any visual system':

 

IMG_3715 (1).jpg


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#13 Adam Long

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Posted 25 June 2020 - 06:15 AM

Also, had another look at η CrB / Σ1937 last night, this time with the addition of a 180mm/ 7" central obstruction. At 436x, this was sufficient to turn the elongated egg into a heavily notched peanut shape.


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#14 happylimpet

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Posted 26 June 2020 - 11:12 AM

I imaged eta CrB a couple of times in May - these were my best results on the night of the 15th.

 

Colour image, drizzled at 1.5x (so 0.090"/pix) using my 12" skywatcher newtonian.

 

2020-05-16-0024_9-NJH-Lum_AS_P1_lapl4_ap1_Drizzle15.png

 

And then splitting this into the RGB frames, this is the blue:

 

Blue_of_2020-05-16-0024_9-NJH-Lum_AS_P1_lapl4_ap1_Drizzle15.png

 

 

and using an iterative gaussian sharpening on this frame:

 

Blue_of_2020-05-16-0024_9-NJH-Lum_AS_P1_lapl4_ap1_Drizzle15_BLUE-itgauss.png

 

Finally at 2x, but with 'nearest neighbour' so you can still see the original pixels:

 

Blue_of_2020-05-16-0024_9-NJH-Lum_AS_P1_lapl4_ap1_Drizzle15_BLUE-itgauss-2x.png

 

As someone said, stelladoppie had it at 0.36". Looks about right - 4 pixels at the drizzled sampling.

 

Might be worth knowing that even at ~60 degree altitude (as i recall) the blue image still benefited hugely from using an ADC - this might be worth considering for visual observations too.


Edited by happylimpet, 26 June 2020 - 11:15 AM.

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#15 Adam Long

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Posted 26 June 2020 - 12:22 PM

This are great, thanks! The first two are very similar to what I remember seeing at the eyepiece. The 'peanut' view with increased  central obstruction was very similar to your unsharpened blue light image.

 

Does the ADC affect the colour of the first shot too? Was definitely at the yellow/ orange end of the spectrum to my eye.



#16 happylimpet

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Posted 26 June 2020 - 03:39 PM

This are great, thanks! The first two are very similar to what I remember seeing at the eyepiece. The 'peanut' view with increased  central obstruction was very similar to your unsharpened blue light image.

 

Does the ADC affect the colour of the first shot too? Was definitely at the yellow/ orange end of the spectrum to my eye.

Cheers - ADC shouldnt affect colour, it just gets rid of the rainbow spectrum. See

 

http://www.damianpea...rsion Peach.pdf

 

even at 60 degrees altitude, the stars light is still streaked over 0.7" altitude by atmospheric dispersion, hardly ideal!


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