Observations -24th May 2020

4 months 4 days ago #108950 by flt158
Observations -24th May 2020 was created by flt158
Hello everyone.

On the evening before my 60th birthday, I set up up my William Optics 158 mm F/7 apochromatic refractor and its accompanying WO 70 mm F/6 small apo in my back garden.

1. I searched diligently for the razor sharp 3.9% illuminated crescent Moon low in the northwestern sky. At the time Luna was of -5.7 in magnitude. Its distance was about 387,000 kms from Earth. And its angular diameter was 30.8'. Initially many clouds were passing by in that area of the sky. But joy was to be had when I observed our Moon at 11X in the small apo as a very faint crescent. In the main refractor at a mere 40X, I could make out 1 large crater and some very small ones along the extremely narrow terminator. I have since checked that the large crater must have been Petavius. Of course there was no sign of its marvellous rille. But I am thoroughly amazed I could see any detail at all on our nearest neighbour!

2.I then set out to observe both Venus and Mercury. I experienced great joy when Venus "popped" into view through various gaps between the mischievous clouds as a extremely thin crescent. The 3.6% illuminated crescent was, at the time, 45,435,000 kms from Earth and her magnitude was -4.2. That's quite a bit fainter than -4.7 earlier during the month of May. Her angular diameter was very large at 54.9". I only used my 28 mm 2" eyepiece which gives me 40X on her. The seeing was very bad with much shimmering even at that power. Still it was a real pleasure to observe our nearest neighbouring planet one more before she leaves our evening skies. I promise I will try to continue to observe Venus over the coming evenings should the skies remain relatively clear.

3.I was not expecting to observe any detail with regards to Mercury. The Messenger's distance was 155,279,000 kms from us. Its magnitude was -0.4 and its angular diameter was minuscule at 6.5". But I was pleased to notice its 62% illumination using my Pentax 10 mm eyepiece which yields 112X. It definitely had a gibbous phase alright. Because of the shimmering conditions Mercury has flashing all sorts of colours. But I was happy making out its gibbous phase at some vital moments.

I only have 3 doubles which I have never observed before that I wish to share with you all. Each of them were found within the boundaries of Corona Borealis.
Before I start I should also say I had a very successful split of Izar and Castor at 112X. As a result I knew I was going to have a good night of splitting doubles.

All figures are from www.stelledoppie.it



4. Struve (STF) 1935 may be an uncertain double but it is a very fine spectacle. Magnitudes: A = 9.9. B = 10.2. Sep = 8.6". PA = 289 degrees. I had the slightest split at 40X. But from 112X, 140X and 167X, I kept thinking B had an orange hue. Other observers might see it differently - and that's fine. I thought A was white.

5. STF 1941 stands alone as my favourite new double of the night. Magnitudes: A = 9.7. B = 9.8. Sep = 1.4". PA = 289 degrees. As soon as I had noted this uncertain binary before my evening commenced, I knew I was going to be in for a real treat! I could see the 2 suns touching at 112X. This was followed by a smidgen of a black gap between the 2 stars at 140X. At 167X I figured both stars have the slightest of a yellow-white hue.

6. Finally, as midnight drew near, I observed a true binary called GRV 903. Magnitudes: A = 9.1. B = 11.1. Sep = 69.2". PA = 243 degrees. With that wide separation I had no difficulties seeing A & B split at 40X of course. But the spectral classes are A = K2. B = K7. So I knew I had to go up in magnification. At 112X, 140X and 167X I could easily see A was orange and B was one of those enigmatic almond brown stars. Sweet! GRV stands for John Greaves. I'm sorry it has not been possible to discover when he lived.

I hope to see more doubles in Corona Borealis.
It most certainly is a very fine constellation for these great stars.

I have 2 carbon stars for you. Both are within the boundaries of Corona Borealis.

7. Much to my embarrassment I have never observed in my entire life the variable star R Coronae Borealis. High time to put that right!
Also much to my surprise I never realised that it is a carbon star - albeit not a very obvious one.
On the famous website www.aavso.org the good people there say its spectral class of C0. So it must be a very hot star.
For beginners I would like to share what most folk have discovered.
On having done some further research by reading Robert Burnham's Celestial Handbook Volume 2, I discovered that there is up to 67% carbon on the star's atmosphere.
That is official enough for me. It's a carbon star. So off I went to find it.
As the star is bright in magnitude at about 6.0 or a little bit fainter, I had no problems finding it at 11X through my William Optics 70 mm F/6 small apochromatic refractor.
R Coronae is directly north of Delta Crb by a short distance. I did find it has an orange hue which is not strong at all even at magnifications 112X, 140X, 167X and 225X. The higher I went the more distinctive the colour became though - which is normal.
However it still counts as a carbon star even though Burnham says that the authorities in the past classify it as type F7, G, or even M.
The star has had a very colourful history because its sudden decline of its magnitude since it was first observed by Edward Pigott who lived from 1753 to 1825. He discovered R Crb in 1795.
Burnham states that it is a very remarkable variable star. It stays at maximum magnitude throughout most of its cycle. But then it suddenly begins to fade and in a few weeks and it could drop down to magnitude 15. Indeed it has been known to fluctuate erratically during the last 150 years.
R Crb acts like a reverse nova.
A dark soot cloud appears to be the most popular theory as to what causes the major dimming of the star.
The cloud covers the star causing it to dim.
So there must be all sorts of strange goings on within R Crb.
That's why it has had over 300,000 observers throughout its history on the AAVSO website.

8. My 2nd carbon star on Corona Borealis is V Coronae Borealis. Its spectral class is C6 or N2. As midnight occurred it meant I could start my 60th birthday celebrations.I was observing V Crb at just 40X through my main 158 mm refractor at the time.
Then my smartphone had to be answered.
A good friend wanted to wish me Happy Birthday which was fair enough.
But I had enough time to see that V Crb has a fairly decent orange colour.
I did observe this carbon star back in May 2002. So it was nice to find it once again.

As far as I know, there are no more carbon stars in this compact constellation.

R Coronae Borealis is my 91st carbon star.

9 to go to 100!

By the way I am counting IY Comae Berenices as a carbon star.On Simbad its spectral class is C.

Thank you for reading this report.

Clear skies from Birthday Boy, Aubrey.
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4 months 4 days ago #108953 by Fermidox
Replied by Fermidox on topic Observations -24th May 2020
When searching for info on John Greaves, who should turn up but yourself Aubrey ;)

www.cloudynights.com/topic/638241-grv-58-and-stf-72/

he does seem to be a contemporary observer, with articles published as recently as 2019. There was a Savilian professor of astronomer at Oxford going by the same name in the 17th century, but doubtful if that's your man :)

Finbarr.
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4 months 3 days ago #108954 by flt158
Replied by flt158 on topic Observations -24th May 2020
Hi Finbarr.
I thank you very much for reminding me of who John Greaves is.
I remember posting that original discussion on Cloudy Nights.
I just had so much happening yesterday as you might imagine celebrating.
There was so little time to do any research.
GRV 903 is such a simple and wide double star; it made me wonder how it could be that a contemporary astronomer could have discovered it in recent times - especially with those vivid colours.
There doesn't seem to be much information on Google about the John Greaves who is very much alive.
However there is enough information about the guy who lived 3 centuries ago.
A real mystery indeed!

It seems we have some clear skies again tonight.
So after observing Venus and Mercury I hope to find more nice doubles in Corona Borealis.

Kind regards to you, Finbarr.

Aubrey.
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4 months 3 days ago #108957 by Until_then-Goodnight!
Replied by Until_then-Goodnight! on topic Observations -24th May 2020
Hi Aubrey, 

Very many thanks for your detailed report. Your descriptions of the Moon, Venus, and Mercury were great. Also, I very much enjoyed reading all about R Coronae Borealis. You've really made the most of that area of the night sky. 

Congratulations on observing your 91st Carbon star, and it won't be long until reach 100.

Clear skies, 

Darren. 
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4 months 3 days ago #108958 by flt158
Replied by flt158 on topic Observations -24th May 2020
Hello everyone again. 
I should have pointed out my observation of IY Comae Berenices before now. 
I should have had some discussion regarding this star here on our Irish website. 
The star hardly varies in magnitude at all. 
No one on www.aavso.org has bothered with it. 
But on Simbad they say at first that it is a spectral class C star. 
Thereafter various observers' make it M, K or even F. 
I would beg to disagree with them. 
When I observe IY Com it definitely has that tangy orange hue which many carbon stars have. 
So for me it's a carbon star. 
Please do feel free to disagree with me. 
One man on Cloudy Nights doesn't accept that the star is a carbon from historical records. 

Please do check out other websites if you wish. 
In fact I would urge you to do so. 
I first observed IY Com on Saturday May 9th May. 
So it was my 90th carbon star. 

R Coronae Borealis is number 91. 

Best regards, 

Aubrey.
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4 months 2 days ago #108959 by Until_then-Goodnight!
Replied by Until_then-Goodnight! on topic Observations -24th May 2020
Hi Aubrey, 

I hope all is well. I've done a little bit of digging on IY Com, and I thought I would send you on a link I found. Whether it will shed some light on its colour classification is uncertain because as you rightly point out there are lots of different opinions on it, but the 2012 paper, which was published in the Observatory, claims it is not a Carbon star and explains why. 

Here is the link:

adsabs.harvard.edu/full/2012Obs...132..356G

I'll try to find out where that conversation went, and I'll provide an update.

The sky looks good for tonight :) 

 Chat soon, 

Darren. 

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4 months 2 days ago #108960 by Until_then-Goodnight!
Replied by Until_then-Goodnight! on topic Observations -24th May 2020
I should probably have mentioned that the info you're looking for can be found in page 357. In addition, I've attached a screenshot that illustrates the source where the confusion came from - reference number 9.

I've not read it yet, and I'm sure much of the information contained in it will go over my head... Just like the info in the 2012 article, but at least we're getting somewhere. Someone with more knowledge than me will understand the details, and might be able to explain the data. 

Clear skies, 

Darren. 
Attachments:

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4 months 2 days ago - 4 months 2 days ago #108961 by Until_then-Goodnight!
Replied by Until_then-Goodnight! on topic Observations -24th May 2020
OK, that didn't take too long. As only one paper has cited that 2012 paper. So, it seems like the 2012 paper has not made much of an impact. Of course, I could be wrong. 

In addition, I went through the 1997 paper to try and find the information that the 2012 draws attention to it. Now I'm not saying it's not there, but I can't find it any mention of the star. I searched HIP 60999; HD 108815, BD 182617, and IY Com, but nothing showed up???? 

The plot thickens! 

How does SINBAD list it? 

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4 months 2 days ago #108962 by flt158
Replied by flt158 on topic Observations -24th May 2020
Hi Darren.
Simbad says C first.
Then says K9 on the more detailed page.
AAVSO says M.
Guide 9.1 DVD says M2.
I don't see red at all.
IY Com varies between 7.4 and 7.6.

Oh and I have the scope set up.

Best regards, Aubrey.
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4 months 2 days ago #108963 by Until_then-Goodnight!
Replied by Until_then-Goodnight! on topic Observations -24th May 2020
Many thanks for this Aubrey,

I'll use some of those other SINBAD identifiers to search the 1997 paper. 

We'll see where that brings us. 

In the meantime, there's some observing to be done :) 

Best of luck for tonight! 

Darren. 
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3 months 2 weeks ago - 3 months 2 weeks ago #109032 by Until_then-Goodnight!
Replied by Until_then-Goodnight! on topic Observations -24th May 2020
Hi Aubrey,

I thought I'd send you a quick update on my search for a definitive answer on IY Com and its status as a Carbon star. 

You might recall that Griffin (1998:357) dismisses HD 108815 as a Carbon star because he states that

"The SIMBAD main heading for the object calls it "Carbon Star". That may have arisen from a misapprehension that the presence of the star in a paper - Guglielmo's et al., (1997) - with the words 'carbon stars' in its title implied that all stars mentioned in it were of that type  - which is not so; the authority for such a description is not otherwise apparent."

However, I have searched through Guglielmo's et al., (1997) with all 20 of SIMBAD's identifiers associated with IY Com, and the search function has failed to identify any of the 20 identifiers in the 1997 paper. I can dig deeper into Griffin's claim, but could this be why Griffin's paper appears to have made little impact - it has only been cited once since it was first published.

I have also discovered that the paper that Google Scholar identifies as citing Griffin (1997) is Abushattal, A. A., Docobo, J. A., & Campo, P. P. (2019). The Most Probable 3D Orbit for Spectroscopic Binaries. The Astronomical Journal, 159(1), 28. However, their bibliography references a different 1997 paper: Yoss, K., & Griffin, R. 1997, JApA,18, 161.

In other words, Griffin's (1997) paper that claims that HD 108815 is not a Carbon Star appears not to have been cited since it was published. That tells its own story!

I'll keep digging over the next few weeks and I'll keep you posted. 

Kindest regards,

Darren.
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3 months 2 weeks ago #109033 by flt158
Replied by flt158 on topic Observations -24th May 2020
Thank you very much for all that you are doing, Darren.

Having observed IY Comae on 2 occasions, I still seem convinced that it is a carbon star. That's because of its delightful tangy orange colour - which I believe is characteristic to many other carbon stars. I don't believe M class stars exhibit such a hue.

I seem to remember from somewhere that the GAIA spacecraft studied 1 billion stars in the Milky Way.
A lot of these stars are summarised on Simbad.

Perhaps that will help you out some way, Darren.
Perhaps not!

Very best regards,

Aubrey.
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3 months 2 weeks ago - 3 months 2 weeks ago #109037 by Until_then-Goodnight!
Replied by Until_then-Goodnight! on topic Observations -24th May 2020
You're more than welcome Aubrey, and very many thanks for pointing me towards the GAIA information. I'll have a look there too.

On a related note, I was all set-up last night to do some observing, but by the time I went out the clouds blocked out the stars : (

Maybe tonight?

All the best,

Darren.
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3 months 2 weeks ago #109039 by flt158
Replied by flt158 on topic Observations -24th May 2020
Ha Ha, Darren!
I was nearly setting up my own scope after sunset too on Saturday night!
I had been talking to a swimming friend of mine on the phone.
And I wandered out into the back garden and couldn't help noticing we had a clear sky.

But as soon as I had finished the phone call, the high clouds covered most of the sky. Boo Hoo!

The latest sunset is coming up very soon.
Tonight the Sun sets at 21.54.

And yes! There does seem to clear skies tonight Sunday.
But it might be the only clear night of the coming week!

Clear skies to all,

Aubrey.
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3 months 2 weeks ago #109040 by flt158
Replied by flt158 on topic Observations -24th May 2020
100% overcast here.
No observing tonight Sunday 14th June.
Will check about Monday night.

Aubrey.
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3 months 2 weeks ago #109041 by Until_then-Goodnight!
Replied by Until_then-Goodnight! on topic Observations -24th May 2020
Likewise. I've just come in from the back garden, and will have to settle for an early night. Hopefully, I'll get a clear sky as a birthday present tomorrow.

Clear skies,

Darren.


 
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3 months 2 weeks ago #109045 by Fermidox
Replied by Fermidox on topic Observations -24th May 2020

flt158 wrote:  
The latest sunset is coming up very soon.
Tonight the Sun sets at 21.54.


According to timeanddate.com, sunset in Limerick is at 22.02 every evening from the 20th to the 28th. I had been under the impression that the latest sunset was about the 15th June, with the earlier sunrises contributing to the longest day on the 21st. However it seems the earliest sunrises are from the 11th to the 22nd, every day at 5.10. Interesting if a little confusing.

Finbarr.
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