Polar coordinates of solar system

[DaveC426913]

I was perusing an astronomy homework site and came across a question in which they are asked to plot the positions of the 3 inner planets on polar graph paper. They are then asked questions about visibility and time of day in Earth's sky.

The table:

[FONT="Courier New"]
Location Venus Earth Mars
   1      280   270   310
   2      325   300   324
   3       18   330   338
   4       68     0   352
   5      115    30     6
   6      165    60    20
   7      213    90    34

What strikes me as odd about this table is that it has the planets going around the sun clockwise. Either
- this is to be viewed from below the solar system's South pole looking up
- the sequence of 7 is last to first.
- the graph coords should be labelled in counterclockwise direction
Whichever way, it's going to be pretty confusing to figure out when the planets can be seen when.

Am I missing something?

 

[Filip Larsen]

Mayby I'm missing something, but if you use the standard polar conversion

$$\left(x,y\right) = r \left(\cos(\theta), \sin(\theta) \right)$$

the planets do go counter-clockwise as expected. For instance, Earth go from from a position on the negative y-axis at 1, over a position at the positive x-axis at 4, to a position on the positive y-axis at 7 (around half a year).

 

[DaveC426913]

Mayby I'm missing something, but if you use the standard polar conversion

$$\left(x,y\right) = r \left(\cos(\theta), \sin(\theta) \right)$$

the planets do go counter-clockwise as expected. For instance, Earth go from from a position on the negative y-axis at 1, over a position at the positive x-axis at 4, to a position on the positive y-axis at 7 (around half a year).

Ah. Ok, so c] the coords are labelled counterclockwise, (and if I understand you correctly, 0 is at the bottom.)

I'd just assumed I'd start with 0 at the top and label degrees clockwise around the graph. But it appears there is a convention to polar coords then.

Thanks.

 

[Filip Larsen]

Ah. Ok, so c] the coords are labelled counterclockwise, (and if I understand you correctly, 0 is at the bottom.)

No, zero angle is normally to the right. See http://en.wikipedia.org/wiki/Polar_coordinate_system or http://mathworld.wolfram.com/PolarCoordinates.html for some helpful diagrams.

 

[DaveC426913]

No, zero angle is normally to the right. See http://en.wikipedia.org/wiki/Polar_coordinate_system or http://mathworld.wolfram.com/PolarCoordinates.html for some helpful diagrams.

Right. Got it.