Stellarium

Sun moves with stars on the celestial sphere

Asked by Farzad Khosrownia

Hi.

Thanks for providing such a fantastic program.

I am playing around with this as Spring Equinox is approaching. I have the physical location where the zero hour will be - where the sun is directly overhead on the Equator. It is 12.25 degrees East of Prime Meridian.

I am trying to simulate this by speeding up the clock. I had expected the Sun to be approaching the Equator on the Celestial Sphere and along the Ecliptic. But, The Sun seems to move together with the fixed stars and seems to be locked at the zero hour and where the Ecliptic intersect the Equator. This doesn't seem to be normal to me and I think there must be a setting that I have not chosen properly.

Can you please help?

By the way, I have set the location to E 12.25 and N 0.0 degrees to simulate being at the precise location and kept my local time to Pacific Time where I am actually located.

Thanks in advance.

Farzad

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Bogdan Marinov
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Best Bogdan Marinov (daggerstab) said : 		#1

About the Sun appearing to be on the intersection of the celestial equator and the ecliptic line: this is so only around the equinoxes. :) At the lowest "fast-forward" speed, you are seeing the movement of the Sun and the stars caused by the Earth's rotation. If you increase the time rate (by repeatedly clicking the "fast forward" button) or if you use the date/time window to advance with days instead of with hours, you'll see the Sun leaving the intersection point and progressing along the ecliptic line.

You can turn off the ground (G) and the athmosphere (A) and switch to equatorial mount (Ctrl+M) to see it better.

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Farzad Khosrownia (khosrownia003) said : 		#2

Thanks Bogdan Marinov, that solved my question.

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Farzad Khosrownia (khosrownia003) said : 		#3

Thank you for your response.

In case of the location of the Equinox I had made an error in computing the longitude. The actual longitude was 176.25 degrees East. When I set the location there the Sun does pass through the Zenith flawlessly.

And when I speed up the motion, the Sun does look like it is moving along with the stars. But this could be because the relative movement is too small with slower animation than it is with faster animation.

Farzad