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R Leonis observed

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#26 Rutilus

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Posted 21 April 2022 - 03:25 AM

Was out again last night taking a look at R Leo.  I also observed R Serpentis, another mira type 

variable that is heading towards maximum brighness over the next few weeks.

R Ser was very easy to find in the finder scope, I estimated its brightness at around mag.7.5.

Very interesting to compare the eyepiece view against R Leo.  R Serpentis appeared more

pale orange to me last night. It's worth checking out R Ser as it's so easy to find at the moment 

in binoculars. Below is last nights photo's with R Serpentis (left) and the more colourful R leo.

 

Attached Thumbnails

  • R-Ser-20-04-2022.jpg

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#27 flt158

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Posted 21 April 2022 - 09:47 AM

In your opinion, Rutilus, would you estimate R Leonis at magnitude +8.0 from your image above?

It seems there is one observer on www.aavso.org who has estimated it at +8.4.

Whereas I thought it had reached +8.0 on Tuesday night.

Further back another observer estimated is at 8.0. 

 

By the way, R Leonis is effortlessly easy to see right not at 11x in my small 70mm apo.  

 

However on Wednesday night I could not observe S Leonis as there was too much high cloud in the area. 

It is another M class star which is far dimmer than R Leonis. 

 

Thanks for the heads up on R Serpentis.  

 

Super images as always. Thank you from Aubrey. 


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#28 Rutilus

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Posted 21 April 2022 - 01:43 PM

Hi Aubrey.  I take my images in JPEG mode, and find it very difficult to make an accurate 

magnitude estimate of red stars like R Leo.  In fact from memory, I  think that JPEG format 

should not be used if you are wanting to determine the magnitude from an image.
It can be done with a DSLR camera, the AAVSO has a manual detailing the methods to be used,

but  I always prefer to make the magnitude estimate by  visual means.

It comes as no surprise to me (and I even expect it) to see the magnitude estimates for R Leo to

vary by quite a bit.  When I was running a variable star group, I would receive estimates for red stars

such as the mira types that would vary by up to one full magnitude between the observers. 

 

Myself, I always  tended to over estimate the brightness of the mira stars by around 0.2 - 0.3 magnitude,

compared to the average when all the observations were lumped together.  So seeing such differences

between observers is what I fully expect to see.


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#29 flt158

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Posted 21 April 2022 - 02:01 PM

Thank you very much for this insight, Rutilus. 

You are most certainly more experienced at estimating the magnitudes of variable stars. 

 

I was comparing R Leonis to the 8.4 magnitude F2 star called SAO 98782 and the 7.6 mag F8 star SAO 98794. 

I found that R Leonis appeared to be half way in mag between these 2 stars.

 

I will try again next week as I'm away for the weekend.  

 

Best regards! 


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#30 flt158

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Posted 22 April 2022 - 11:49 AM

Hello again. 

 

I'm content that my estimated magnitude on R Leonis is correct. 

Someone else on www.aavso.org is giving it a magnitude of +8.0. 

 

Best regards from Aubrey.


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#31 Rutilus

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Posted 24 April 2022 - 07:27 AM

Thank you for the report that R Leo is currently at mag 9! I have started following a few variable stars with my 50mm binoculars, and my limiting magnitude is about 8.0. So, with R Leo, I have been waiting for it to appear, and have not seen anything yet. I suppose soon it shall be visible for me! For those morning observers out there, Chi Cygni is quite bright at the moment.

Chi Cyg has started to rise above my observatory walls in the early morning hours.

Took this image this morning. While still quite low down in the sky, Chi was very bright

and had noticable red colour in my 8x44mm binoculars. 

Attached Thumbnails

  • Chi-Cygni-24-04-2022.jpg

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#32 flt158

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Posted 25 April 2022 - 09:45 AM

Thank you to each and every one of you who have been following this R Leonis post thus far - and all the "likers" too.  

 

Last night (Sunday) I estimated that the star R Leo has now reached 7.7 in magnitude. 

It seems that every time I observe it this star is becoming brighter.

 

Estimating M class variable stars can be great fun. 

Why now give it a go? waytogo.gif 

 

Clear skies from Aubrey.  


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#33 robin_astro

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Posted 27 April 2022 - 11:41 AM

I took a quick look at it with the spectrograph last night. Here it is (in blue) with the passbands of the Johnson-Cousins photometry filters overlaid. I have also overlaid a template spectrum of an M8iii giant which it matches very closely currently. 

 

RLeo_20220426.png

 

The real action though takes place outside our view in the IR.  Here is my same spectrum again (sorry about the change of colour!) which stops at 7800 Angstrom, the limit of my spectrograph but  with the M8 template extended to ~ 1 micron wavelength , near the limit for silicon technology.

 

RLeo_IR.png

 

It really takes off, ending up about 400x brighter than in the green which explains the extreme bloating in *skyguy* 's fast achromat image

https://www.cloudyni...ved/?p=11828542

(Imagine how bright it would look if we had "silicon technology eyes"!)

 

Cheers

Robin


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#34 robin_astro

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Posted 27 April 2022 - 12:07 PM

I meant to include the image of the spectrum. Here it is (with a big gamma stretch to show the faint blue end without burning out  the red end)

 

RLeo_20220426_raw_spectrum.jpg

 

 

Cheers

Robin


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#35 flt158

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Posted 27 April 2022 - 12:28 PM

Thank you for your contributions, Robin!

It's a real honour to read them both. 

I'm thrilled to notice that right now R Leonis is an M8 star. 

It must be swelling in size until it reaches maximum magnitude. 

 

By the way I'm noticing now on www.aavso.org that one other first-time observer has estimated that R Leonis' magnitude is 7.7. 

I hope to observe this delightful variable star tomorrow night Thursday and beyond. 

 

Very best regards from Aubrey.  


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#36 robin_astro

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Posted 27 April 2022 - 12:46 PM

 

It must be swelling in size until it reaches maximum magnitude. 

 

 

Hi Aubrey,

 

Actually, perhaps counterintuitively, the star is actually shrinking at the moment !   As it compresses, the temperature increases which increases its luminosity but mainly shifts the light more towards visible wavelengths.  This graph from wikipedia shows how diameter, temperature, total luminosity and visual brightness changes with Miras through the cycle

 

https://en.wikipedia..._pulsations.png

 

Cheers

Robin


Edited by robin_astro, 27 April 2022 - 12:49 PM.

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#37 flt158

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Posted 27 April 2022 - 06:23 PM

Thank you, Robin. 

You certainly have me scratching my head! scratchhead2.gif

If R Leonis is shrinking, why is it getting brighter?

 

My Burnham book says on page 1071 that R Leo is an M-type giant star. 

That's all I can understand. 

 

When you say that the star compresses, do you mean it is shrinking?

Okay its temperature increases and its luminosity increases also. 

 

Thank you for the Wikipedia link on pulsations. 

 

I wonder if one was inside a spacecraft approaching R Leonis, how would we see the star change in appearance during its 312 day period?

 

I shall look forward to your next reply.

 

Best regards from Aubrey. 


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#38 robin_astro

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Posted 28 April 2022 - 05:32 AM

 

If R Leonis is shrinking, why is it getting brighter?

 

 

When you say that the star compresses, do you mean it is shrinking?

Okay its temperature increases and its luminosity increases also. 

 

Stars are a balancing act between the radiation pushing out trying to explode the star and gravity pushing in trying to crush it. Stars like the sun are in perfect balance but many giant stars tip into instability and pulsate with radiation winning sometimes and gravity winning at other times.

 

When the star is larger, it is less dense and easier for the radiation to escape so gravity starts to win, shrinking the star.

As the star shrinks it becomes denser so the radiation cannot escape. This heats the star increasing the temperature. Radiation then starts winning again and the star starts expanding

As the star expands the radiation can escape again and the star starts to cool and begins contracting again.

 

(note this is only a "hand waving" description and a massive oversimplification, for example this only happening in particular layers of the star, not the whole star but hopefully gives an idea of what is going on)

 

The visual brightness of Miras is particularly sensitive to changes in temperature. Remember that we only actually see a fraction of a percent of the radiation from the star, almost all of it is beyond the sensitivity of our eyes in the IR. This means a small change in temperature can make a big change in the amount of light in the visible (think of heating up lump of metal, we only see it once it is red hot). Added to this, as the star cools it is easier for Titanium Oxide molecules in the star to absorb the visible light.  You can see this in the AAVSO light curve. The change in brightness in B is much larger than in  I 

 

RLeo_BI.png

 

Cheers

Robin


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#39 robin_astro

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Posted 28 April 2022 - 05:54 AM

 

 

The visual brightness of Miras is particularly sensitive to changes in temperature. Remember that we only actually see a fraction of a percent of the radiation from the star, almost all of it is beyond the sensitivity of our eyes in the IR. This means a small change in temperature can make a big change in the amount of light in the visible (think of heating up lump of metal, we only see it once it is red hot). Added to this, as the star cools it is easier for Titanium Oxide molecules in the star to absorb the visible light.  You can see this in the AAVSO light curve. The change in brightness in B is much larger than in  I 

 

 

In fact if we venture further into the infra-red and look at the H band (in grey) where most of the radiation is we find that the star is actually hardly changing in brightness at all !  What we are seeing with our eyes is effectively just a change in "colour" 

 

RLeo_BH.png


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#40 flt158

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Posted 28 April 2022 - 08:29 AM

Thank you for all this information, Robin. 

 

I will ponder on these points as I seek to understand the variable star R Leonis. waytogo.gif

I must keep learning about these amazing stars. 

 

Very best regards from Aubrey. 


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#41 Rutilus

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Posted 30 April 2022 - 03:58 AM

Had a look at R Leo last night. In my 7x50 finder scope it appears to have faded a bit in brightness.

To the south of R Leo there is a magnitude 7.5 star, R Leo was fainter than this star.  So I estimated

it back at around mag.8.0.

Here is part of a wide angle shot taken with my 80mm f/7 refractor and f/3.3 focal reducer. 

Attached Thumbnails

  • R-Leo-29-04-2022.jpg

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#42 flt158

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Posted 30 April 2022 - 08:14 AM

Super image, Rutilus!

I'm promising to observe R Leonis yet again on Monday night next under clear skies,  

I am that bit sad that our star might be fading now. 

I thought it ought to be reaching magnitude 5 at some stage in the near future. 

We can never tell what these Mira class stars are going to do. 

 

Best regards from Aubrey. 


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#43 flt158

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Posted 30 April 2022 - 09:30 AM

I see Paul Abel of Cloudy Nights has R Leonis a magnitude of +8.0 on www.aavso.org. 

Paul is an excellent astronomer. 

So you must be right, Rutilus! laugh.gif

I might have clear skies on Monday night. 

 

Aubrey. 


Edited by flt158, 30 April 2022 - 03:51 PM.

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#44 Rutilus

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Posted 30 April 2022 - 01:58 PM

Aubrey - Last night I also took a look at R Serpentis. Very easy to find located between beta and gamma.

It was putting on a good show at around mag.7.0, brighter than the mag.7.3 comparison star.

Also Chi Cyg is bright at the moment. Here is a photo taken last night of R Ser with my 80mm 

refractor set-up with some magnitudes included. 

Attached Thumbnails

  • R-Ser-29-04-2022.jpg

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#45 flt158

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Posted 29 May 2022 - 11:45 AM

Hello one and all.

 

At last! A clear night after 4 solid weeks of overcast cloud. So I travelled to the Wicklow mountains with 3 friends with my William Optics 158mm f/7 apochromatic refractor. The winds were not too bad – 12 km/h. I started observing at 10.30pm (local time) and ended at precisely midnight on Friday night 27th May 2022. The Great Lion is beginning to get that bit lower in the western sky. The whole constellation is now more and more lopsided as he departs from me.

 

I thought it would be good fun to re-observe R Leonis. It’s so easy to locate some 6˚ west of Regulus. And I asked each of my astronomical friends to check out its colour. After that, I would estimate its magnitude. First it was Paul. He said red. Second was Chris. He said yellow-orange. Third came Michael. He said orange-red. For those who haven’t observed R Leonis, Mr Koch who discovered the star in 1782 stated that it’s a rich rose-scarlet star. And I completely agree with him. Its spectral class varies from M6 to M9.5. Its distance is 370 light years. I am now finding that R Leo is now much brighter than I estimated on the 7th April 2022 (mag: 9.0). On Friday night I estimated its magnitude as a whopping +7.2! I used a 6.9 mag star and a 7.6 star to give this estimate. And I feel I was being conservative. I have recorded its current magnitude on www.aavso.org . I will try to observe it again if I can before Leo disappears altogether.

 

Clear skies from Aubrey. 


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#46 flt158

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Posted 07 June 2022 - 10:33 AM

Hello, one and all.

 

This is due to be my final post regarding R Leonis. 

The variable star is now extremely low close to my north western horizon.

I had to wait until after 11pm local time before it finally appeared in both my William Optics 70mm f/6 and my 158mm f/7 apochromatic refractors. 

As the sky darkened minute by minute, R Leo eventually popped out. 

Its rose-scarlet colour was easily seen once again. 

Over on www.aavso.org I have recorded a magnitude of +6.1. 

What a star this is!

On the night of the 7th April R Leo was just +9.0. 

It is now brighter than 19 Leonis (6.4 mag). 

 

It has been such a privilege to observe this variable for some months. 

I feel a little bit sad that my observations have now come to an end. 

But roll on late winter 2023 when I will reacquaint myself with this wondrous star once again.   

 

I close by thanking you all for reading each of my reports, and also for encouraging me personally to observe R Leonis! applause.gif  

 

Clear skies from Aubrey.  


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#47 lurkist

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Posted 17 July 2022 - 07:46 PM

Hello, one and all.

 

This is due to be my final post regarding R Leonis. 

The variable star is now extremely low close to my north western horizon.

I had to wait until after 11pm local time before it finally appeared in both my William Optics 70mm f/6 and my 158mm f/7 apochromatic refractors. 

As the sky darkened minute by minute, R Leo eventually popped out. 

Its rose-scarlet colour was easily seen once again. 

Over on www.aavso.org I have recorded a magnitude of +6.1. 

What a star this is!

On the night of the 7th April R Leo was just +9.0. 

It is now brighter than 19 Leonis (6.4 mag). 

 

It has been such a privilege to observe this variable for some months. 

I feel a little bit sad that my observations have now come to an end. 

But roll on late winter 2023 when I will reacquaint myself with this wondrous star once again.   

 

I close by thanking you all for reading each of my reports, and also for encouraging me personally to observe R Leonis! applause.gif  

 

Clear skies from Aubrey.  

In the New Year coming, Jan '23, and also around Dec '23, you'll get your chance to see this Zodiacal object through two consecutive maxima, but next one after that is around October '24 when it won't rise until after midnight, and after that you might have to wait till '26 (Juney), possibly '27 (Arpily), but predicting that far ahead for Miras is a bit foolish, at least.  If you pick some Mira to follow you'll have to remember this though, you'll not get full cycle lightcurves often for near Ecliptic objects.  Then again, circumpolar aren't always easy depending on how low they get when they are under the pole, especially if the nearest conurbation lies North.  Most of the naked eye at maxima ones don't pass much below 13th and 14th magnitude, if that, but if you want to follow full some full cycle you will have to remember that too, as there are not many Miras that are about 12th magnitude at minimum and not near the Ecliptic.  R Aquilae has a relatively bright minimum, for example, but is season dependent.

 

I once had a bash at following Miras, starting with this very star, R Leonis, and although I'm not usually prone to old Mr Purkinje and his effects, and had experience of visually estimating variable stars for some little time, my estimates in one session were all over the place!  I think it was the psychophysiological contrast with 19 Leo that got me, each making the other seem bluer and redder than they would normally.  I went back to just doing CVs till I got bored of 'em.


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#48 Rutilus

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Posted 18 October 2022 - 03:51 AM

For early morning risers. R Leo was easily seen this morning in the eyepiece of my

6 inch f/8 refractor. It was brighter than the nearby magnitude 9.2 comparison star.

Took a quick image as the sun was rising. 

Attached Thumbnails

  • R-Leo-18-10-2022.jpg

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#49 KMA

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Posted 18 October 2022 - 10:26 AM

Nice properly oriented image.

AAVSO reported magnitudes clearly shows

declining brightness and

old Bulletin (AAVSO) predicts minimum

about December 16.

best wishes

KMA


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#50 flt158

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Posted 18 October 2022 - 05:34 PM

Brilliant image of R Leonis, Rutilus. 

I cannot wait to observe it once again as soon as possible. 

It's one of the few stars I see as truly red with my apochromatic refractor. 

 

And thank you, KMA, for reminding us that R Leo is fading in magnitude. 

I had a feeling that was true.  


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