Re: Calculating the Equation of Time and other Solar Parameters

2014-02-23 Thread Roger Bailey 
Thanks Kevin,

A quick review demonstrated how useful your work can be for folk like us. Here 
is a specific example. I have been working with solar and lunar ephemerides 
date from the JPL Horizons website. http://ssd.jpl.nasa.gov/horizons.cgi#top 
This site provides a wealth of data that the user can customize for their own 
purposes. The problem is the user does not know how the data was calculated nor 
how it is to be used  The Explanatory Supplement helps but it is difficult to 
understand.  One simple example is understanding a solar data compilation that 
provided among other things Right Ascension and Declination. But I really 
wanted the EQT. Your formula 9 in Part 1 gave me the simple relationship, 
obvious in hindsight that I was looking for, the conversion of RA to EQT.

I look forward making good use of your work. Thank you for making it available.

Thanks again,
Roger Bailey
Walking Shadow Designs




From: Kevin Karney
Sent: Sunday, February 23, 2014 11:32 AM
To: sundial@uni-koeln.de List
Subject: Calculating the Equation of Time and other Solar Parameters


Dear Friends


I have spend many happy hours during this wet, wet winter investigating and 
learning how to calculate all the solar parameters that a gnomonist might 
possibly need  - Equation of Time, Declination, RA, Altitude, Azimuth, Time of 
Sunset/Rise, etc, etc.


I have been surprised to find that - with traditional calculation methods and 
an absolute minimum of astronomical information -  it is possible to calculate 
everything from first principles to a surprising degree of accuracy.


Other than location and local time, only six pieces of astronomical information 
are required - obliquity, eccentricity, Sun’s GHA at 1/1/2000, longitude of 
perihelion, a single precessional constant and the length of the tropical year. 
Accuracies for the EOT are +/- 2 seconds of time For altitudes/azimuths, less 
than 1 minute of arc - much better than needed by most gnomonic problems.


If any of you are interested in such calculations, I have loaded a document 
with all the astronomical theory and background plus the code onto my website
www.precisedirections.co.uk/sundials
The code is written in Python, a language available on every type of computer, 
which is very easily understood, quite easily learnt and very easily translated 
into any other coding language you might like.


If you own an iPad or iPhone, and are prepared to buy a cheap little app called 
Pythonista, the code will extract locational & time information from your phone 
- so you do not even have to input this to get your calculations done


You might also like to see a graphic of a civil mean time horizontal dial, 
which I think is called a hectomoros dial,  that is destined for my garden. 
This is also on the website.


Enjoy
Kevin





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Re: Calculating the Equation of Time and other Solar Parameters

2014-02-23 Thread Bill Gottesman 
Kevin,

I am excited about your article "Basic Astronomy for the Gnomonist."  It
will take some time to digest, but it seems to have a very nice graphic
analysis for the many formulas and solar positioning we deal with.  I
appreciate you making this reference available.

I think what you call a Hectoromos dial is what I have heard described as a
Singleton dial.  Here is a link to a similar (vertical) dial at the
University of Vermont.  Fred Sawyer wrote about the Hectoromos dial in an
early NASS compendium.  I think Plato might have had something to do with
it.

-Bill


On Sun, Feb 23, 2014 at 2:32 PM, Kevin Karney  wrote:

> Dear Friends
>
> I have spend many happy hours during this wet, wet winter investigating
> and learning how to calculate all the solar parameters that a
> gnomonist might possibly need  - Equation of Time, Declination, RA,
> Altitude, Azimuth, Time of Sunset/Rise, etc, etc.
>
> I have been surprised to find that - with traditional calculation methods
> and an absolute minimum of astronomical information -  it is possible to
> calculate everything from first principles to a surprising degree of
> accuracy.
>
> Other than location and local time, only six pieces of astronomical
> information are required - obliquity, eccentricity, Sun's GHA at 1/1/2000,
> longitude of perihelion, a single precessional constant and the length of
> the tropical year. Accuracies for the EOT are +/- 2 seconds of time For
> altitudes/azimuths, less than 1 minute of arc - much better than needed by
> most gnomonic problems.
>
> If any of you are interested in such calculations, I have loaded a
> document with all the astronomical theory and background plus the code onto
> my website
> *www.precisedirections.co.uk/sundials
> *
> The code is written in Python, a language available on every type of
> computer, which is very easily understood, quite easily learnt and very
> easily translated into any other coding language you might like.
>
> If you own an iPad or iPhone, and are prepared to buy a cheap little app
> called Pythonista, the code will extract locational & time information from
> your phone - so you do not even have to input this to get your calculations
> done
>
> You might also like to see a graphic of a civil mean time horizontal dial,
> which *I think* is called a hectomoros dial,  that is destined for my
> garden. This is also on the website.
>
> Enjoy
> Kevin
>
> ---
> https://lists.uni-koeln.de/mailman/listinfo/sundial
>
>
>
---
https://lists.uni-koeln.de/mailman/listinfo/sundial

CORRECTION Calculating the Equation of Time and other Solar Parameters

2014-02-23 Thread Kevin Karney 
My website is …
http://www.precisedirections.co.uk/Sundials
with a capital S for Sundial

Sorry
K---
https://lists.uni-koeln.de/mailman/listinfo/sundial

Calculating the Equation of Time and other Solar Parameters

2014-02-23 Thread Kevin Karney 
Dear Friends

I have spend many happy hours during this wet, wet winter investigating and 
learning how to calculate all the solar parameters that a gnomonist might 
possibly need  - Equation of Time, Declination, RA, Altitude, Azimuth, Time of 
Sunset/Rise, etc, etc.

I have been surprised to find that - with traditional calculation methods and 
an absolute minimum of astronomical information -  it is possible to calculate 
everything from first principles to a surprising degree of accuracy. 

Other than location and local time, only six pieces of astronomical information 
are required - obliquity, eccentricity, Sun’s GHA at 1/1/2000, longitude of 
perihelion, a single precessional constant and the length of the tropical year. 
Accuracies for the EOT are +/- 2 seconds of time For altitudes/azimuths, less 
than 1 minute of arc - much better than needed by most gnomonic problems.

If any of you are interested in such calculations, I have loaded a document 
with all the astronomical theory and background plus the code onto my website
www.precisedirections.co.uk/sundials
The code is written in Python, a language available on every type of computer, 
which is very easily understood, quite easily learnt and very easily translated 
into any other coding language you might like.

If you own an iPad or iPhone, and are prepared to buy a cheap little app called 
Pythonista, the code will extract locational & time information from your phone 
- so you do not even have to input this to get your calculations done

You might also like to see a graphic of a civil mean time horizontal dial, 
which I think is called a hectomoros dial,  that is destined for my garden. 
This is also on the website.

Enjoy
Kevin---
https://lists.uni-koeln.de/mailman/listinfo/sundial