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Noon Sun on the Shortest Day


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About this observation
Andrew Paterson
Time of observation
22/12/2019 - 12:04
Observing location
Hill Head
iPhone 6s
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The sun from our conservatory at local noon on the day of the northern winter solstice. 
Declination -23deg 26’17”

Altitude 15deg 44’ 26”


Xilman's picture

You quote positions to  a second of arc.

a) Is that of the centre of the sun at the instant of observation?

b) Does the altitude take into account atmospheric refraction?

c) Is altitude above the horizon your topographic horizon, or an ideal sea-level horizon?  If the latter, have you taken your altitude above sea-level into account?

Yes, I´m a pedant --- guilty as charged --- but I was taught to quote my results only to a justifiable precision.  As a practicing scientist I try to adhere to that advice.

Andrew Paterson's picture

Thank you for the comments- I only really posted this image as a bit of fun to mark the winter solstice. 
I did not measure the altitude of the sun at local noon, I obtained the data from the sky guide app on my phone, which gives the data to second of arc precision. 
The position of the sun is given for the centre of the solar disc. Positions are calculated without taking account of the effects of refraction. As a result the altitude of the sun at sunset on a sea horizon is -0.7 deg because of refraction and the semi-diameter of the sun. 

Xilman's picture

My comments were very much tongue-in-cheek and I hope you took them in that spirit. My apologies if you misunderstood.

I´m often guilty of quoting numbers to spurious precision.

Andrew Paterson's picture

I suppose I should have twigged!

Attached is a great ima  ge of spurious accurate - the position of a gate at Manado Airport, Indonesia. It is given to 0.001” of arc which is approximately 3cm!

Merry Christmas 

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