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T Lyncis observed - 7th & 8th April 2020

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3 years 11 months ago - 3 years 11 months ago #108602 by flt158
Hello everyone.

The fairly clear weather appears to be continuing. On both nights, 7th and 8th April I was observing in my back garden with my William Optics 158 mm F/7 apochromatic refractor plus my W/O 70 mm F/6 small apo. Both scopes are supported by a Berlebach Planet alt-az mount. Mirror diagonals are fitted to both scopes. Before sunset occurred at 8.13 local time, the temperatures were a very warm 16˚ Celsius. By the end of the observing session it was 6˚ C.

1. Where else to start only with Venus. Her magnitude has now reached -4.6. She is getting nearer and nearer – 88,654,000 kms from Earth. 42.1% illuminated and an angular diameter of 28.2”. Through the 70 mm small apo I could make out a simple half phase. But in the main scope at 40X, I could easily make out the 42% lit world. The planet appeared totally white from 112X onwards in every way and those cusps are still extended by quite a bit. But of course I did push the magnifications upwards. At 225X and 280X the shimmering was increasing. But I am used to that at this stage.

2. After dinner I found Castor and Pollux yet again. The 3 stars of Castor looked brilliantly glorious at 112X. As we all know the 2 main bright stars are white, but the 3rd has a distinctive red hue. Excellent!

From here on all these figures can be checked out on www.stelldoppie.it

3. Then eventually, my wife Valerie, joined me for these spectacular doubles in Lynx. The first is 38 Lyncis. Strong admirers of double stars will never tire of observing this magnificent true binary. Magnitudes: A = 3.9. B = 6.1. Sep = 2.5”. PA = 229˚. The B component is simply gloriously split nice and is good and tight at 112X. Sometimes I use higher magnifications, but not this time. There is a lovely black gap of space in between both white stars. What a true gem!

4. Stf 1333 was next. It may be an uncertain double, but what a sight it is! Magnitudes: A = 6.6. B = 6.7. Sep: 1.9”. PA = 65˚. It truly is another true gem split at 112X. I went no higher. 2 eyes looking back at me through the telescope. And so close to 38 Lyncis.

5. I trust that at the end of the year 2020 Stf 1338 will be one of my favourite observations. Certainly right now it is my new top favourite double star of the year. It is a true binary which makes it even more attractive to me personally. Very easy to locate as it is 2˚ from 38 Lyncis. It is even caught in the 70 mm apo at 11X. Magnitudes: A = 6.7. B = 7.1. Sep = 1”. PA = 322˚. There is no split at 40X of course. But something is beginning to happen at 112X. But no split then either. What a true transformation is to be had at 140X! The tiniest black gap is seen. Higher magnifications are very much more decisive. 167X, 225X and 280X are perfectly suitable to still maintain a tight and wonderful split. But I am still very surprised to see a separation at 140X. After all the split is a mere 1 arc second. I don’t think I will ever get used to it. The spectral classes of both stars are F2v and F4v. Therefore both stars are yellow-white. Valerie enjoyed these wonderful doubles. I'm very sure Mr. Struve hugely loved each of these doubles when he first observed them.

6. I have found my first ever carbon star in the constellation of Lynx. T Lyncis is enormously difficult to find though - if you don’t have GoTo. And I don’t either. If you want to seek out this carbon star, don’t do what I did initially by starting at Castor and Pollux. There are too many empty areas in that high section of the sky. Instead start at Alpha Lyncis. Its magnitude is +3.1 – easily visible with our own eyes. Using your finder scope head westwards by about 2˚ to a fairly bright trio of stars in northern Cancer which are of 7th magnitude: Sigma 1, Sigma 2 and Sigma 3 Cancri. Continue to move westwards by 1˚ to a 7 star asterism whose brightest stars are of 7th magnitude too. You have almost arrived. Again head west by about one degree and you will see a compact 4-star asterism. Go west for the last time by another 1˚ and you should see T Lyn with 2 bright stars very close to it with magnitudes 7.2 (SAO 60759) and 8.2 (SAO 60752). T Lyncis is a good orange carbon star alright. I have estimated its magnitude are +9.9 on www.aavso.org . I used 2 stars TYC 2474 74 (mag 9.8) and TYC 2474 298 (mag 9.9) to reach this conclusion. By the way, T Lyn varies between +8.8 at maximum to +13.5 at minimum. The star has a B-V Colour Index of 2.45. Therefore its temperature is 41˚ Kelvin. I would like someone to explain the meaning of this particular B-V index. It might be good for others to learn – not just me. Also I would like to learn more about the spectral class of T Lyn. It varies between C5,2e and C7,1e. Is C7 redder than C5? I’m sure it is. Astronomers estimate that T Lyn is 20,762 times bigger that our Sun. That must be when the star is at its brightest magnitude. What a colossus! I have one last fact for you. Our Hipparcos spacecraft has given the distance of T Lyn: some 327 light years or a little over 100 parsecs.

I don’t know when I will observe T Lyncis again. But I have enjoyed seeing it 2 nights in a row albeit with a Full Egg Supermoon.

I would love to find another carbon star in Lynx. Please watch this space.

Dublin, Ireland is now covered by a high haze of thin clouds. So I might not be observing any time soon. But it has been a most extraordinary 5 out of 6 clear nights over recent times. Has it not? Maybe we will have more clear skies over Easter. Who knows?

Thank you for reading my report. I know I have been highlighting these doubles for a second time. But each one is superb.

Comments are still very welcome.

Clear skies,

Aubrey.
Last edit: 3 years 11 months ago by flt158.
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3 years 11 months ago - 3 years 11 months ago #108603 by lunartic_old
Replied by lunartic_old on topic T Lyncis observed - 7th & 8th April 2020
Nice report.  You must be getting better weather where you live than I do here.  The mist last night was quite dense and the stars pretty dim, even the moon had a serious halo.  Venus was looking slightly out of focus, maybe living close to the sea doesn't help.
Paul

Programming today is a race between software engineers striving to build bigger and better programs, and the universe trying to produce bigger and better idiots. So far, the universe is winning.

Rich Cook
Last edit: 3 years 11 months ago by lunartic_old.
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3 years 11 months ago #108604 by flt158
Replied by flt158 on topic T Lyncis observed - 7th & 8th April 2020
A decent Swedish guy on Cloudy Nights is informing me that the Simbad website has estimated T Lyncis is more like 8500 light years away.
It appears that our esteemed spacecraft can't get such figures right.
So maybe that is going to deter me from highlighting such calculations in the future.

Yes, Paul. There were some moments of late last night. That is certainly true around my horizons - both east and west.
But Lynx is very high in the south western sky at the time of my observation.
By 10 pm, I just couldn't see those 3 stars Sigma 1, 2 or 3 Cancri through my 70 mm apo. So I ended at that point.
The haze is now worse on Thursday and probably over Easter.

Valerie greatly enjoyed the doubles in Lynx.

I do hope you will get a good price for your binoviewers, Paul.

Happy days from Aubrey.
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3 years 11 months ago #108611 by Keith g
Replied by Keith g on topic T Lyncis observed - 7th & 8th April 2020
That's a nice report Aubrey. From my understanding the B-V index is used to numerically express the colour of a star. B is for Blue and V is the total 'bolometric or visual' light from a star. Basically the less B that is subtracted from the V (visual) magnitude of the star, the bluer it will appear. If a lot of the blue wavelength of light from the star is absent, the redder the star will appear. I believe carbon stars have a high B-V index, as the carbon will absorb a lot of blue light, hence appearing very orange or red at the eyepiece

Maybe this will help a little:
en.wikipedia.org/wiki/Color_index

Also regarding Lynx, I have only ever observed one object every spring time for the last few years, It's galaxy NGC2683. This is an edge on spiral galaxy at about magnitude 9.1, just north of Sigma 1,2,& 3 Cancri you mentioned. I love looking at this relatively easy galaxy, what gets me is the sense of loneliness about it, floating in space at over 30 Million light years away. Perhaps you could try it soon on your way to T Lyncis.

Keith.. 
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3 years 11 months ago #108614 by Until_then-Goodnight!
Replied by Until_then-Goodnight! on topic T Lyncis observed - 7th & 8th April 2020
Hi Aubrey,

Very many thanks for sharing another detailed report with us. Stf 1338 sounds like a beauty, and I'd love to see it for myself. Also, congratulations on finding your first carbon star in Lynx, and it's great that you provide details on how to find it.

We now need the sky to clear!

All the best,

Darren.
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3 years 11 months ago #108616 by flt158
Replied by flt158 on topic T Lyncis observed - 7th & 8th April 2020
Hi Keith.
It's always good to hear from you.
I have seen that coloured table some time in the past.
But it doesn't include carbon stars.
It would be nice if it did.
But as it stands, M class has a B-V Colour Index of 1.4.
Therefore, logically carbon stars will be a higher figure.
I asked the question because some people over on Cloudy Nights seem to be interested in such matters.

That fine galaxy NGC 2683 probably requires a dark site to observe it successfully.
Maybe it's one for the Sugarloaf Car Park whenever we get back to it.

Happy Easter to you, Keith.

Clear skies from Aubrey.

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