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PostPosted: Wed Feb 01, 2017 1:05 pm 
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Joined: Thu Jun 02, 2016 11:32 am
Posts: 430
Location: New Farnley, Leeds lat 53.8N long 1.6W
“Life is but a…
Life is but a…
Melancholy flower
Melancholy flower”

A fifty year old memory rises at me. I am remembering a nonsense song and a hot, crackling camp fire under an August sky blazing with improbable meteors. It is hard to see a connection between then and now. Maybe it’s because the melody is “Frere Jacques”. Now, we are driving a familiar road through the French countryside at night in freezing January.

After twenty minutes my eyes are reasonably dark adapted and I watch Procyon trundle Orion across a cold, dark corridor between a house and a tall fence. We are near the Pyrenees here. The sky is black and the stars are sharp. They prick my eyes gently, like white spicules of hoar frost on a black breeze. Betelgeuse is the shot-through shoulder of Orion. If you stare for long it gets bigger, brighter and it spreads like blood on a trolley.

How do you compare white stars such as Procyon with red stars? They contrast like bone and blood. Betelgeuse is variable. How bright is it? My quick estimate tonight is Procyon minus one. That means Betelgeuse is magnitude 0.46. I make estimates on six other nights here; three are 0.36, two are 0.46 and one is 0.56. A rounded average of all seven estimates makes Betelgeuse 0.4 this January. Irrationally, it seems brighter than that. Without a doubt other observers are getting different impressions.

Like flesh and memory, all our estimates are fallible and we see things as we hear things, subjectively. I seem to hear the world whisper one thing to me and yet you hear something different.

“Life is butter
Life is butter
Melon cauliflower
Melon cauliflower”


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PostPosted: Fri Feb 03, 2017 7:49 am 
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Joined: Sat Sep 24, 2016 10:16 pm
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A piece of advice I frequently give to newcomers to variable star observing is to not worry if your observations are slightly out of step with those reported by others. The sensitivity of the eyes to red light varies from person to person and each observer will have different observing conditions in terms of the amount (and colour) of light pollution.

In any case, for most of the time, we are primarily interested in *when* a star is brightest or faintest, the exact magnitude at such times being less important.

For red stars, it is best just to take short glances at them, rather than stare. This reduces the impact of their colour.

Betelgeuse can be a tricky variable star to observe since its comparison stars are some distance away on the sky. The biggest problems can occur when Betelgeuse, Procyon and Aldebaran are at very different altitudes above the horizon, such as when Orion is still fairly low in the SE sky. At such times, hazy skies can dim the three stars by different amounts. It then becomes a case of waiting an hour or two for them all to gain a similar altitude (and hope it doesn't cloud over).

Some people say that naked-eye variable stars are good targets for beginners. I disagree. They may be easy to locate, but making brightness estimates of many of them can often be tricky.


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PostPosted: Fri Feb 03, 2017 3:30 pm 
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Joined: Mon Jan 09, 2006 11:05 am
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Location: Lancashire
As you will know Tracie, bringing a star out of focus into a small disc gives us a better perception of the star's colour.
Does the same technique assist in determining a star's variability?

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PostPosted: Sun Feb 05, 2017 4:20 pm 
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Joined: Sat Sep 24, 2016 10:16 pm
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Some variable star observers do find it easier to defocus the stars slightly so that they appear as disks.
This can bring the star brightness below the colour sensitivity level of the eyes and thus removes the colour factor when comparing the brightness of the variable and its comparison stars.
The limitation of this method however is that it makes the stars appear less bright and so the variable cannot then be followed down to the faintness levels achievable when the stars are focussed.


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PostPosted: Mon Feb 06, 2017 6:42 pm 
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Joined: Sat Dec 11, 2004 8:18 pm
Posts: 6506
Location: Manchester
Dear Bob et al
I enjoyed your eulogising (hoping that's a good word to use - I never actually wrote it before).You provoked some interesting responses.Astronomy provides tremendous scope for anyone ( or certainly many of us) and from just unaided eye stuff, to extremely sophisticated equipment and a maze between) or even armchair stuff in a warm indoors.
Variable stars are undoubtedly fascinating and its easy to understand someone falling under their spell. One of my old acquaintances seemed to get get most of his kicks, showing beginners wonders of the night sky. I tended to prefer doing astronomy with one or two friends on the dark-ish Pennine Hills, or home alone in our back garden. Now I get my fun observing the day-time Sun.
Best wishes from Cliff


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PostPosted: Mon Feb 06, 2017 7:19 pm 
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Joined: Thu Jun 02, 2016 11:32 am
Posts: 430
Location: New Farnley, Leeds lat 53.8N long 1.6W
Thanks Cliff, more star stories to follow, if I'm spared! Kind thoughts, Bob


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