Planet Angles relative to Sun

[BDL]

Hello everyone, I'm new here looking for some information.

Imagine you're on the pole star looking "down" on our solar system. You see the sun in the middle with the planets all around it. I want to write a personal programme to show the relative positions of the sun and all it's planets on any chosen day. So if I stand on Polaris and look at our sun on a particular day, what would the angle be between the sun and Mercury, and Venus and Earth and all the rest of them on that day?

I remember coming across this series of angles once as a reference for one particular date but I can't remember what it's called.

Please can someone help?

Many thanks,

Brian

 

[Dave Lloyd]

Hi Brian, welcome. I wouldn't know how to start programming that software😁 but there's lots on here who could. I imagine if you have a base position for a certain date it's easy enough to extrapolate planetary placings using length of year etc. 

 

[michael8554]

Pretty sure there's already Solar System Simulation software out there. 

Michael 

[Owmuchonomy]

There are plenty of ‘apps’ that can do this for you or at least give you the data. Sky Safari for example.

[Demonperformer]

Hi, Brian, and welcome to SGL.

Determining the planetary positions in relation to each other is fairly straight forward. Take a look at this wikipedia page. But if you want to see them specifically from Polaris, you would also have to consider the inclination of the entire solar system in relation to your line of sight ... it might be seen edge-on (as the Jovian satellites from earth) or face-on (as the Uranian satellites from earth) or anywhere in between. I have no idea how what that angle is or how it would be calculated.

Enjoy the journey.

[BDL]

Thanks everyone for your replies. Yes, I'm aware of the software all around doing similar to what I want to do. But I know exactly what I want to see from my programme. And all I need is the "starting point" so that I can plot all the planets at the right distances from the sun and the correct angles between a line drawn from each of them to the sun on one specific reference date. Then, as David Lloyd pointed out, I can do the maths to place them where they would be on any other date. Don't need any help with the programming thanks. I might have kicked the ball off in the wrong direction when I mentioned looking at our solar system from Polaris: what I should have said is from a distant point on a line drawn through the sun at 90 degrees to the solar system's plane. What is the starting point I'm looking for? (And what is it called? I'm sure I saw a name for it long ago.)

When I've produced the programme I'll make a copy available so you can see what I'm going on about.

Cheers,

Brian

[Paul M]

21 minutes ago, BDL said:

What is the starting point I'm looking for? (And what is it called? I'm sure I saw a name for it long ago.)

I think orbital calculations usually start from a point in an  orbit called the ascending node and from there you will need to know the angular distance to the orbits perihelion point. The angle between the two is called the argument of perihelion.

These values can be found in an orbiting body's orbital elements.

They are different for each body and change with time!

Given a start point for each planet a simple set of orbital period ratios will get you what you want but for accuracy there is a lot to consider.

See the works of Jan Meeus for guidance of calculating orbital mechanics.

[CentaurZ]

The line from Polaris to the Ecliptic (plane of the Earth's orbit) is tilted by about 24˚ from the perpendicular. You would want to be theoretically observing from the North Ecliptic Pole, or the North Pole for the Invariable Plane of the Solar System.

I've written a program similar to what you are seeking based on data from the book "Planetary Programs and Tables from -4000 to +2800" by Pierre Bretagnon & Jean-Louis Simon, with a foreword by Jean Meeus.  Another source I use is "Astronomical Algorithms" by my Belgian friend Jean Meeus. The first book should be quite sufficient for your task. The latter is considerably more comprehensive.

 

 

Edited July 14, 2019 by CentaurZ

[BDL]

To everyone who has commented on my original question - thank you all for your help. There is so much in your replies that it will take me some time to research and digest it all! During this time I will also be starting the programme design. I'll report on significant progress (of likely interest only!) as I go. Any more input will be very welcome. And I look forward to sending you the finished product when (and if) I succeed.

All the best,

Brian

[Captain Scarlet]

Hi Brian 

I have done precisely this for myself fairly recently, also because I wanted to build “my own” tool rather than use the various available apps.

I found the most accessible (actually very accessible) guide was that by Paul Schlyter, at this link

https://stjarnhimlen.se/comp/ppcomp.html

There’s also another version of the same page with more worked examples IIRC.

After finishing that project, I got the Jan Meeus book, and in retrospect I think I did it in the right order. Schlyter’s merhods get you to around 2 arcminutes of accuracy, and are quite easy to follow, whereas Meeus is a bit more involved and benefits from one having done some slightly simpler groundwork. Meeus will allow you to get as accurate as you like though, and I’m using it to refine my own project.

Good Luck, and keep us informed how it goes...

Cheers, Magnus

[BDL]

Thanks for that Magnus. It looks like everything I need! Brilliant.

All the best,

Brian