How to determine the position of the suns equator

[batema (Mark)]

I have a Yr 12 student who is trying to measure the rotation of the sun at different latitudes based on sunspot observation. Could someone tell me how or where we can work out the suns equator so she can work out the latitude of the sunspot and then the speed of rotation.

thanks

mark

[renormalised (Carl)]

Here's something I think you'll be very interested in and will help your student immensely. Have a look at the rest of the site as well. It's a resource you should serious think about incorporating into the curriculum. If you don't know about it already.

http://www3.gettysburg.edu/~marschal/clea/Solarrotlab.html

[renormalised (Carl)]

In any case, if it's of any help, the Earth's orbit lies in a plane 7.2 degrees inclined to the equatorial plane of the Sun. Since the Sun differentially rotates depending on the latitude you measure, the given definition of the equator is the line tracing the circumference of the Sun where the rotation is equal to the average time taken for the Sun to rotate i.e. 25.4 days.

Here's something which might help, but it will be more to your benefit as it will most likely be a little too advanced for a Yr12 student to follow. Although, if they're good at maths, give them a go at it

[sheeny (Al)]

I use solar active region maps. The one I used to use has been discontinued though.

I suggest google "active region maps" and have a look at what's available. The one I used to use showed the active regions and the solar lat and long lines, so the tilt was obvious, and I knew which way to flip my images to match the map. The few I looked at this morning appear not to show the tilt, so I don't know if they do show but the sun happened to be orthogonal to us at present or not. Time will tell.



Al.

[batema (Mark)]

I have found it thank you Al. Also thank you Carl for the links. I have forwarded the CLEA link to the girl. We use the moons of Jupiter and the pectral Analysis and they are fantastic so thank you.

Mark

[Merlin66 (Ken)]

http://www.atoptics.co.uk/tiltdld.htm
http://www.petermeadows.com/html/software.html

These may be of interest.