Sunspot plotting and angular velocity

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Discussion Overview

The discussion revolves around the methods for plotting sunspots on a diagram with degrees, focusing on calculating their positions in terms of longitude and latitude. Participants explore various approaches to determine these positions, including assumptions about the Sun's rotation axis and the use of observational data.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • One participant suggests that plotting sunspots involves assuming the Sun's rotation axis is perpendicular to the observer, which is a good approximation, but notes that repeated observations and radial velocity measurements provide better accuracy.
  • Another participant emphasizes the need to measure the position of the sunspot relative to the known axis of rotation, indicating that geometry is involved in this process.
  • A participant expresses confusion about the geometric aspect of determining both longitude and latitude of sunspots.
  • One suggestion involves using trigonometry on a spherical grid to find the positions, although another participant questions the clarity of this approach.
  • Another participant proposes using a protractor to estimate positions, while expressing uncertainty about whether a better method exists.
  • It is mentioned that obtaining the apparent position of sunspots on the Sun's disk might require photographic analysis, suggesting that a camera and computer could yield good results.
  • A participant considers using a transparent image of a disc with longitude and latitude markings to plot sunspots manually, questioning the feasibility of this method.
  • One participant recommends searching online for resources related to sunspot coordinate determination, mentioning a specific website that may provide useful information and software for plotting sunspots.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and approaches to the problem, with no consensus on the best method for plotting sunspots or calculating their positions. Multiple competing views and methods remain present in the discussion.

Contextual Notes

Participants have not fully resolved the mathematical and geometric steps necessary for determining sunspot positions, and there are differing opinions on the best tools and methods to use.

ExoP
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Hi!

I was wondering how you plot the sunspots on a diagram/template with degrees on it. In other words, I want to plot a sunspot and calculate the position of it in degrees. I have no idea how to do it but I think it includes the assumption that the rotation axis of the Sun is perpendicular to us. By knowing that we need to compute the apparent longitude of the spot on the Sun. I think that this can be done by measuring the position of the spot..and finally compare the photos taken of the Sun for maybe one week and then get the angular velocity by difference in the logitude position. How do I calculate the longitude position? :S

Thanks!
 
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I think it includes the assumption that the rotation axis of the Sun is perpendicular to us.
That is a very good approximation, but repeated observations how sunspots move and radial velocity measurements are even better. The axis of rotation is known, you can look it up somewhere. Afterwards, you just have to measure the position of the spot relative to this axis. This is just geometry.
 
How is the geometry, that is basically the problem I'm having? I need both the longitude and latitude.
 
Take a sphere, make a grid on it, use trigonometry. Sorry, I don't see the issue.
 
I was thinking of using a protractor, but it may exist a better way to estimate their position
 
You'll need the apparent position (on the "disk" of the sun, as it appears to us) first - I guess a camera (and then a computer to analyze the picture) will give good results.
 
How can I do it by hand? I was thinking of using a transparent image of a disc with the longitude and latitude degrees on, and then plot the spots on it. Afterwards, I want to determine the location by looking at those spots. That may be possible right? :)
 
Exop, if you do a web search on "sunspot coordinate determination" you'll find some useful links.

One that caught my eye takes you to "Peter Meadow's Astronomy Sunspot Location" page. It might be worthwhile browsing it (this is not a personal endorsement, but the site does cover what I think you're looking for and may give you some leads). I believe that Meadows has been published in Sky & Telescope regarding his sunspot plotting software.
 

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