astronomical/ephemerides algorithm
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astronomical/ephemerides algorithm
Hello, I was wondering if anyone can point me to a software/algorythm/calculator of Ephemerides. I don't need an online service but the formulas to create the software or an existing App.
Start by Googling Jean Meeus and any of his works, e.g.
ASTRONOMICAL ALGORITHMS - DOWNLOAD FREE
Jean was pretty much the "go to" guy in this field for the latter half of the twentieth century. Not sure how active he is now but I'm sure the maths still works...
His wiki entry with some more links is here:
https://en.wikipedia.org/wiki/Jean_Meeus
ASTRONOMICAL ALGORITHMS - DOWNLOAD FREE
Jean was pretty much the "go to" guy in this field for the latter half of the twentieth century. Not sure how active he is now but I'm sure the maths still works...
His wiki entry with some more links is here:
https://en.wikipedia.org/wiki/Jean_Meeus
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Yes, I'm aware of that book. I'm also reviewing some other documents
OK off the top of my head the only other author/source you might want to investigate is Fred Espenak, he often chucks mathematical stuff including some basic 
programs into the technical appendices of his works, but he's very much an Eclipse specialist.
Good luck
programs into the technical appendices of his works, but he's very much an Eclipse specialist.Good luck
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I' m using Meeus' algorythms : OK
For sundials and equation of time I'm using Denis Savoye algorithms (some mistakes in the first edition, but corrected in the last edition).
I wrote some tens of programs.
Implementation in QBasic of Meeus helped me to discover a bug in QBasic when I was computing the Julian day.
Implementation on a pocket Casio 25+ helps me to verify the sundials when I'm visiting some of them and discovered many sundials with bad realisation and important drifts. I'm working with a target of 3minutes or less precision for my own sundials, which is very low. Only a little fraction of gnomonists are able to reach that precision. Remind that every angle error of 1° may lead to a 4 minutes drift.
Formulas may be found too in the old ephemeris books perfectly verified.
Debug perfectly your softwares.
Much pleasure during nights with the well named "Calculs astronomics"
For sundials and equation of time I'm using Denis Savoye algorithms (some mistakes in the first edition, but corrected in the last edition).
I wrote some tens of programs.
Implementation in QBasic of Meeus helped me to discover a bug in QBasic when I was computing the Julian day.
Implementation on a pocket Casio 25+ helps me to verify the sundials when I'm visiting some of them and discovered many sundials with bad realisation and important drifts. I'm working with a target of 3minutes or less precision for my own sundials, which is very low. Only a little fraction of gnomonists are able to reach that precision. Remind that every angle error of 1° may lead to a 4 minutes drift.
Formulas may be found too in the old ephemeris books perfectly verified.
Debug perfectly your softwares.
Much pleasure during nights with the well named "Calculs astronomics"
I can safely say I'm sure I've never seen the word "gnomonist" before!
Yes, Fred has some good data, I flew him on an eclipse flight a few years ago.
Yes, Fred has some good data, I flew him on an eclipse flight a few years ago.
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Two words are used in french to describe the profession consisting in doing sundials :
1. The Gnomoniste's work is to calculate the exact position and informations who figure on the sundial.
2. The "cadranier" decides and realises the look of the sundial. Doing it beautiful is important to read the time correctly and easily.
Many people are the gnomonist and the cadranier unless you have a team working with you. But the gnomonist finally decides and has the responsibility of the final subdiaphragmatic.
The origin of the word "gnomonist" is "gnomon". The "gnomon" is a vertical stick giving the height of the sun. The first sundials were mostly "gnomons" until people realised that you have better to use a polar style parallel to the north-south poles axis or derivated systems of polar style.
1. The Gnomoniste's work is to calculate the exact position and informations who figure on the sundial.
2. The "cadranier" decides and realises the look of the sundial. Doing it beautiful is important to read the time correctly and easily.
Many people are the gnomonist and the cadranier unless you have a team working with you. But the gnomonist finally decides and has the responsibility of the final subdiaphragmatic.
The origin of the word "gnomonist" is "gnomon". The "gnomon" is a vertical stick giving the height of the sun. The first sundials were mostly "gnomons" until people realised that you have better to use a polar style parallel to the north-south poles axis or derivated systems of polar style.
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Exactly ! But imagine the shade of a style passing on the top of that awesome stick , parallel to the poles' axis. (That style is going toward North direction and angle with the horizontal plane is latitude).
The very important point of that stick is the top.
At equinox -spring or fall- the movement of the shade on a plane -ie wall or ground- of any fixed point - ie the end of a branch - is a straight line who gives you your orientation aso of the wall.
Ideally you should use the poles' axis but, seen from the sun producting the shade, the angular distance to your style is neglectable.
The very important point of that stick is the top.
At equinox -spring or fall- the movement of the shade on a plane -ie wall or ground- of any fixed point - ie the end of a branch - is a straight line who gives you your orientation aso of the wall.
Ideally you should use the poles' axis but, seen from the sun producting the shade, the angular distance to your style is neglectable.
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Of course ! Eratosthenes knew that earth was spheric, and understood what latitude is !
He did not use a verticasl stick but a vertical hole in Syena at summer solstice and distance to Alexandria was counted in camel very regular steps. He calculated then the earth radius :-))
He did not use a verticasl stick but a vertical hole in Syena at summer solstice and distance to Alexandria was counted in camel very regular steps. He calculated then the earth radius :-))
