# Sunspot plotting and angular velocity

• ExoP
In summary, the conversation is about plotting sunspots on a diagram with degrees and determining their position using the assumption of the Sun's rotation axis being perpendicular to us. The process involves measuring the apparent longitude of the spot and comparing photos taken over a period of time to calculate its angular velocity. The speakers discuss various methods, including using a protractor or a transparent image of a disc with degrees. They also mention a website that may provide useful information on sunspot coordinate determination.
ExoP
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!

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.

## 1. What is the purpose of sunspot plotting and why is it important?

Sunspot plotting is a way of visually representing the number and location of sunspots on the surface of the sun. This information is important for understanding the sun's activity and how it affects our planet. By tracking sunspots, scientists can better predict solar flares and other space weather events that can impact communication systems and power grids.

## 2. How is sunspot plotting done?

Sunspot plotting is typically done by taking regular images of the sun using a telescope or spacecraft. The images are then analyzed and the number and location of sunspots are recorded on a graph or map. This process is often automated using computer algorithms, but can also be done manually.

## 3. What is angular velocity and how is it related to sunspot plotting?

Angular velocity refers to the speed at which an object rotates around its axis. In the context of sunspot plotting, it is used to measure the speed at which sunspots move across the surface of the sun. This information can help scientists understand the underlying processes that drive the formation and movement of sunspots.

## 4. How does sunspot activity impact Earth?

Sunspot activity can have a significant impact on Earth's climate and technology. Solar flares, which are often associated with sunspots, can cause disruptions in communication and navigation systems, as well as power grids. Additionally, the amount of sunspot activity can affect the amount of solar radiation that reaches Earth, which in turn can impact our climate and weather patterns.

## 5. How do scientists use sunspot plotting and angular velocity to make predictions?

By tracking the number and movement of sunspots, and measuring their angular velocity, scientists can gain insights into the behavior of the sun and make predictions about future solar activity. This information can help us prepare for potential disruptions to technology and infrastructure, as well as better understand the complex processes that drive our sun's activity.

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