Celestia Forums

Hi. I am teaching solar eclipses in my classes and have repeatedly tried to use Celestia to depict what happens when the umbra passes over you. Unfortunately, there are two problems in viewing an eclipse in Celestia from the ground:

1. The moon does not completely obscure the sun. The view in annular, not total ... even when it is supposed to be a total eclipse.

2. The sky does not darken completely at the correct time. I can go to Earth when the umbra is supposed to be and not find the sun covered by the moon at that spot. Rather, the sky will be dark, but the moon will not be covering the sun.

Here is a screenshot of what I mean:



Does anyone have a solar eclipse cel:url that will cover the sun and darken properly?

HELP

Frank

Here is a link to motherlode. Scroll down 2/3 and look for Solar Eclipese 1999.
http://www.celestiamotherlode.net/catalog/scripts.php

You can change the angle of view (the number in the lower right corner of the screen). Hold the shift key down. left click and drag to change the view angle. I read somewere that 32 degrees was normal or how our eye sees the world. Not sure but experiment. When you get the script going hit the space bar to stop were the moon is in front of the sun. Change the view angle to get it the way you want. Note the view angle number. If you are writing a new script you can enter this value to have the moon cover the sun perfectly. NOTE, you will not see the corona.

One last thing learn the keyboard shortcuts. That is the best way to make Celestia preform.

Enjoy
Don

fsgregs wrote:Hi. I am teaching solar eclipses in my classes..

I too have stumbled upon Celestia in the last 24hrs and I'm wanting to use it to show the 11/08/99 eclipse in a class next week. After tweaking the render mode, I've got Celestia working on my laptop, but when I try to show the shadow tracking across the earth, I'm seeing several shadows (sometimes 3 at once) tracking across the globe in all sorts of strange directions.

Has some kind person got some insight into what I'm seeing? Is this:

+ The shadow of something else (looks big!). I'm afraid I've had no joy landing on earth and trying to look up to see what it is (how do you "look behind you?").

+ An artifact of using a non GL render mode (these appear in both the basic and multitexture modes - I'm afraid that the OpenGL mode draws a bizarrely ellipsoid earth and then promptly crashes Celestia)

+ A known bug of some other kind (in which case, with heavy heart, I'll pursue Starry Night or Redshift)

Any help gratefully received

Simon*

Simon,

Exactly what operating system are you running?
What type of graphics hardware do you have?
What version of its graphics driver is installed on your system?

Your description is consistent with a very buggy graphics device driver. You should be able to download an updated version for free from the Web site of the manufacturer of your laptop.

Assuming you're running Windows, you can verify that this is your problem by turning off hardware acceleration and seeing how Microsoft's software graphics drivers show the event.

Under Windows, to turn off hardware acceleration, open the "Display Properties" window. Select the "Settings/Advanced/Troubleshoot" tab. (not the "Troubleshoot..." button). Move the "Hardware acceleration" slider all the way to the left. Click on the "OK" buttons to change the settings in use. This will cause Windows to use Microsoft's Generic OpenGL v1.1 library, which is limited and can't show all of Celestia's eye candy, but seems to have relatively few bugs. It even works on 2D displays, but it draws everything using software and so is quite slow.

Selden

Many thanks - you were right on the button. With no hardware acceleration the artifacts vanish, leaving a single track that intersects Cornwall as expected.

It is dog-slow, but I have the most up to date driver for my laptop (last version 2004!), so short of a new machine I'll have to lump it for now. The up side is a thin black line at Longitude 0!

Cheers

Simon*
p.s. I found the keyboard shortcuts in the help menu!

Unfortunately, the 1999 eclipse when viewed from the ground, does not result in the sky darkening and the sun being completely blocked out. Again, the only effect seen is an annular eclipse, with part of the sun visible. The sky does not go black at the moment of totality.

Please ... Selden or someone ... is this a limitation in Celestia? Does the view from the ground of an eclipse always result in a scene that does not coordinate the darkening of the sky as totality is reached? If so, I will give up and assume I cannot show this in Celestia.



Help!!!

Frank

Frank,

Are you running this script in 1.5.x or 1.4.x ?
I haven't looked at the script itself, but I was just thinking that this may be because of the Sun's position changing in 1.5.0, so the script may need to be modified (if it's using celURL's).

CC

Here's an URL to the very famous solar eclipse of 29 May 1919, photographied by Sir Eddington to test General Relativity. I get an annular eclipse :

cel://Follow/Earth/1919-05-29T14:25:13. ... 51&lm=2050

fsgregs wrote:Unfortunately, the 1999 eclipse when viewed from the ground, does not result in the sky darkening and the sun being completely blocked out. Again, the only effect seen is an annular eclipse, with part of the sun visible. The sky does not go black at the moment of totality.

Please ... Selden or someone ... is this a limitation in Celestia? Does the view from the ground of an eclipse always result in a scene that does not coordinate the darkening of the sky as totality is reached? If so, I will give up and assume I cannot show this in Celestia.



Help!!!

Celestia does not darken the sky during a total eclipse. I *may* have a chance to modify the new atmosphere code in 1.5.0 so that the sky darken in the eclipse.

That you see just an annular eclipse is due to the way that Celestia renders the Sun's corona as a fuzzy halo. I'm working on the 1.5.0 star rendering right now, trying to make it look better; that halo effect will probably go.

--Chris

You can use Stellarium instill they get Celestial to render eclipse accurately.

CELESTIA 1.5.0 pre 1



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CELESTIA 1.4.1



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