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 Post subject: Re: Betelgeuse
PostPosted: Tue Feb 25, 2020 9:17 am 
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Joined: Fri Dec 03, 2004 2:41 pm
Posts: 1462
Location: 55° 57'N: 03° 08'W
Yes Bob, I do.


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 Post subject: Re: Betelgeuse
PostPosted: Tue Feb 25, 2020 12:51 pm 
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Joined: Thu Jun 02, 2016 11:32 am
Posts: 537
Location: New Farnley, Leeds lat 53.8N long 1.6W
The question is ambiguous
I know,
Whether our stellar Betelgeuse
Should glow
Brighter or fainter, that's your cue,
Just so
You can tell me, "Yes Bob, I do."
:P


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 Post subject: Re: Betelgeuse
PostPosted: Tue Feb 25, 2020 1:44 pm 
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Posts: 1462
Location: 55° 57'N: 03° 08'W
Comparing stars both red and blue,
Is a very hard thing to do,
I've looked for rhyme,
And taken my time,
But 'Purkinje Effect' ; I haven't a clue.


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 Post subject: Re: Betelgeuse
PostPosted: Tue Feb 25, 2020 2:48 pm 
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Joined: Thu Jun 02, 2016 11:32 am
Posts: 537
Location: New Farnley, Leeds lat 53.8N long 1.6W
Staring too hard at Purkinje
Could seriously unhinge ye,
So start with one wee Pogson step,
And try it out on Delta Cep,
A star by far more yellowy.


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 Post subject: Re: Betelgeuse
PostPosted: Tue Mar 03, 2020 9:26 pm 
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Location: New Farnley, Leeds lat 53.8N long 1.6W
2020 March 03, 2115 UT. New Farnley, West Yorkshire, UK. Unaided eye, artificial light sources shielded, Moon close to the field shielded. Variable well seen at a reasonable altitude.
Light estimate: Gamma (Bellatrix, Vmag 1.64) +2 (Pogson Step Method). Deduced Vmag Betelgeuse is 1.44.


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 Post subject: Re: Betelgeuse
PostPosted: Fri Mar 20, 2020 8:38 pm 
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Joined: Thu Jun 02, 2016 11:32 am
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Location: New Farnley, Leeds lat 53.8N long 1.6W
Betelgeuse seems to be well on the mend. I estimate it tonight at Vmag 1.14, or possibly a little brighter, see below.
2020 March 20, 20.20 UT. Unaided eye, sky dark but affected by artificial illumination - street lamps shielded by my arm. Light estimate: gamma (Bellatrix, Vmag 1.64) +5 (Pogson Step method). Deduced Vmag Betelgeuse is 1.14 HOWEVER, this is an estimate at the limit of the Pogson Step method and it is easy to get it wrong. I suspect that Betelgeuse might even be a little brighter than that, maybe around Vmag 1.0. I'd like to see some other recent estimates.
Unambiguously, Bob


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 Post subject: Re: Betelgeuse
PostPosted: Thu Mar 26, 2020 8:27 pm 
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Joined: Thu Jun 02, 2016 11:32 am
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Location: New Farnley, Leeds lat 53.8N long 1.6W
While outside giving health workers a clap, I estimated Betelgeuse tonight at about Vmag 0.9.
2020 March 26, 20.00 UT. Unaided eye, sky dark but affected by artificial illumination - street lamps shielded by my arm. Light estimate: Procyon (0.34) 2 (V) 3 Bellatrix (1.64) fractional step method. Deduced Vmag Betelgeuse is 0.86.
Kind thoughts, Bob


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 Post subject: Re: Betelgeuse
PostPosted: Thu Apr 02, 2020 8:59 pm 
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Joined: Sat Dec 11, 2004 8:18 pm
Posts: 6547
Location: Manchester
Christmas 2019, David Frydman mentioned Betelgeuse's unusual variability on the Forum. Others including Bob, BrianL, Nigel & Stella have shown observing interest. I've been a sluggish armchair astronomer, reading in Patrick Moore's 1997 book "Brilliant Stars"; Betelgeuse's slight variability was noted by John Herschel in 1836. Patrick observed variations of 0.0 to 0.9, official catalogues calling it a semi-regular variable with 5.75 year period.
BBC Science Focus (March 2020) "Betelgeuse; is this super-giant about to explode?" says - in Jan & Feb 2020 it reached a record low - 40% its usual brightness, one day "soon" going Super-nova. Currently its variable period is about 14 months. Although it might BANG tomorrow we may be waiting 100,000 years.
Best of luck from Cliff


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 Post subject: Re: Betelgeuse
PostPosted: Fri Apr 03, 2020 6:56 am 
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Joined: Sat Jan 26, 2008 4:03 pm
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Location: Galloway, SW Scotland
It was certainly looking healthy last night, Cliff, lovely through my 9x63 binoculars.

I always imagined that red giants would cool fairly uniformly, but I assume what is happening here is that the star cools a little and then collapses inward a little, releasing more energy, which stokes its fire for a while.

Interesting to see.

Best wishes,

Nigel

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 Post subject: Re: Betelgeuse
PostPosted: Sat Apr 04, 2020 8:03 pm 
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Location: Manchester
Nigel
I'm no expert on variable stars (or other aspects of astronomy for that matter). Although ages ago, I did do a sort of self training trial course for several months before opting to look at planets & DSOs. Back in those old days I doubt Betelgeuse would have attracted my interest because of its considerable brightness - but limited variation & colour complication problems.
I gather even now not everyone thinks Betelgeuse's recent considerable variations in apparent brightness relate to its likelihood of going BANG fairly soon, but might be caused by the star drifting through clouds of gas, dust or even some stuff splurted out by the star itself.
Regards from Cliff


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 Post subject: Re: Betelgeuse
PostPosted: Sun Apr 05, 2020 7:01 am 
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Location: Galloway, SW Scotland
Thanks, Cliff. I hadn't considered the possibility of the star being partly obscured by gas clouds.

Best wishes,

Nigel

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 Post subject: Re: Betelgeuse
PostPosted: Mon Apr 06, 2020 8:54 pm 
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Location: Manchester
Nigel
That's OK but it's only gen I read - and there's more !
American astronomer, Fred Schaaf's 2008 book "The Brightest Stars" provides interesting gen.
After mentioning John Herschel as possibly first to note Betelgeuse's brightness variations, Schaaf goes on that changes were quite dramatic 1836 to 1840, more so 1849 to 1852; bright again 1894.
He says, Robert Burnham Jnr, reckons Betelgeuse had high maxima brightness, 1925, 1930, 1933, 1942 & 1947, but in the decade 1957 to 1967, only slight variations.
AAVSO graphs showed Betelgeuse probably reached mag 0.2 in 1933 & 1942.
Joseph Ashbrook studied Betelgeuse 1937 to 1975 estimating its extreme range -0.1 to +1.1. In February 1957 he noted brightening by 0.4, then dimming back again in two weeks.
Apparently Betelgeuse was noted for unpredictable brightness fluctuations over approximately regular periods. The main period being about 5.7 years with short superimposed periods of between 150 & 300 days.
Best wishes from Cliff


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 Post subject: Re: Betelgeuse
PostPosted: Tue Apr 07, 2020 3:49 pm 
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Joined: Sat Jan 26, 2008 4:03 pm
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Location: Galloway, SW Scotland
Thanks for the info, Cliff; it is certainly unpredictable!

I looked for a visual depiction. The only longer term one I could find was the one below, over a period from 1988 to 2002. Interesting to see!

https://en.wikipedia.org/wiki/Betelgeus ... lgeuse.png

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 Post subject: Re: Betelgeuse
PostPosted: Sat Apr 11, 2020 9:18 pm 
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Joined: Thu Jun 02, 2016 11:32 am
Posts: 537
Location: New Farnley, Leeds lat 53.8N long 1.6W
2020 April 11, 20.55 UT. Unaided eye, sky dark but affected by artificial illumination. Light estimate: Procyon (0.34)-4, Pogson step method. Deduced Vmag Betelgeuse is 0.74.
Kind thoughts, Bob


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