Stellarium

[Grahame]

I've just successfully completed my first landscape for Stellarium, of Richard Creightmore's Beech Hill stone circle in the Ashdown Forest. As Ian says, it's vital to have the picture in 2:1 ratio - I ended up using 4096 x 2048 - and positioning the horizon line midway on the vertical side. I avoided having the black strip at the bottom by using a clone brush to 'copy' the grass and fill in the blank bits at the bottom of the picture.
The main problem I'm having is getting the two edges to marry up properly; there always seems to be a tiny gap visible. But I think this may be an issue with Stellarium v10; there was a message in their forum about the same problem.
If anyone would like a copy send me a PM.

[Ian Pegler]

To view the 1999 eclipse without needing to edit the date and time manually, select Run from your Start menu and copy-paste the following command-line:

"C:\Program Files\Stellarium\stellarium.exe" --sky-date 19990811 --sky-time 11:11:00

Tap the 'J' key once to stop time. If it starts going backwards, counteract this by tapping the 'L' key once.

You will need to select Scale Moon from the Sky and Viewing Options menu, then get rid of the Atmosphere.

Make sure your location is somewhere in the U.K., preferably in the path of totality.

You may need to modify the above command-line if you've installed Stellarium in a different folder.

It is disappointing that this 0.10.0 Beta version has crashed nearly every time I've tried to edit the time and date. Also I have yet to fathom how to report a bug to them. Sometimes it even crashes the display driver.

Also, it would be neat if, during a total eclipse, the atmosphere responded by changing colour. That would be a cool feature, at the moment I have to ditch the atmosphere to see anything appropriate at all.

Ian

[Grahame]

That's pretty neat, Ian. Worked for me with no problems. The totality seemed to last rather a long time though - like a couple of hours or so.

[Grahame]

Ian and myself have both been busy on Stellarium landscapes, and we currently have three available. My two are:


Sighthill stone circle, Glasgow. Built by SF writer and amateur astronomer Duncan Lunan in 1979


Beech Hill stone circle, E. Sussex. Built by Richard Creightmore & Ivan McBeth in 2000

And Ian's one...

Mitchell's Fold stone circle in Shropshire. This features in an article by Ian in the forthcoming Dowsing Today (April 09).

You can download these from the Stellarium landscapes page. Enjoy!

[Ian Pegler]

That's pretty neat, Ian. Worked for me with no problems. The totality seemed to last rather a long time though - like a couple of hours or so.

I've learned a thing or two about this now...

With the latest version of Stellarium (verion 0.10.1 I think) or later, the landscape does go dark(ish) at the appropriate time. So you can run the simulation with the Atmosphere set to ON.

However, the NASA tables don't give local information so it's a question of finding out when the shadow passes over locally - if it happens at all. For this you need to look at the graphical data, provided by NASA. Then, having satisfied yourself that it will happen, you can run the simulation back and forth in time until the shadow appears. However, this can sometimes be a bit of a subtle effect.

Let's do a worked example. First, find the eclipse you're after.

NASA have a Five Millenium Catalog, you can look up.

Note: to convert from negative years, to B.C., ignore the minus sign and add one. For example:

-1999 is 2000 B.C.

This is because there was no "Year zero" in the western calendar.

So supposing we want to look at the eclipse that happened on August 11th, 1999.

You may find it in the Five Millenium Catalog (click here and scroll right down to the bottom) where the entry reads as follows:

09506 1999 Aug 11 11:04:09 64 -5 145 T 0.5062 1.0286 45.1N 24.3E 59 197 112 02m23s

The number on the left is the Catalog Number. If you click on this you get a graphical representation of how the eclipse shadow affects the globe.

The "path of totality" is the thick blue line. If you're standing anywhere on this line you will see 100% totality of a solar eclipse. The best point to stand is marked by the green star. This is the moment of "greatest totality". The time value at the top right marks when the shadow reaches the green star.

If you stand anywhere except the thick blue line, you won't see a total eclipse, but if you stand within the large area indicated on the plan you will see a partial eclipse. The closer you are to the thick blue line, the more you will see. The dotted lines are the "50 percent" lines. If you're standing on one of those you will see a partial eclipse where the Sun is half-covered by the Moon.

Remember that the eclipse shadow moves from West to East.

NASA have a variety of other useful tools which you will find on their eclipse website including a World Atlas of Solar Eclipse Maps and a Javascript Solar eclipse explorer which is pretty useful for telling you when eclipses occur that can be seen from a specified latitude/longitude location.

So it's a case of finding the historical (or future) eclipse you want and jotting down the details (date &time) so that you can find out when the moment of Greatest Eclipse happens, then you use Stellarium to find out when the shadow passes over your site.

DON'T go by the position of the Moon - that's no guide at all. Find out when the landscape turns dark.

Ian

[Ian Pegler]

Mitchell's Fold stone circle in Shropshire. This features in an article by Ian in the forthcoming Dowsing Today (April 09).

The article, as I understand it will be in two parts. The stuff on Mitchell's Fold will appear in Part Two (mid July 09)

Many thanks for sorting this out Grahame.

cheers

Ian


Edited by I.P. 7.3.09 - modified date of Part Two

[Ian Pegler]

Firstly, there doesn't seem to be a way to pause time, at least not an obvious one.

The time rate can be set to zero by pressing the '7' key. It's not the same thing as a pause button though.

Ian

[Ian Pegler]

It took several attempts to line up the image in such a way that East really corresponds to East in the image.

I have recently learned how difficult this is, so here are some tips:

1) Don't use a compass.
2) Read tip no 1 again. Really, don't use a compass.

Some stone circles have magnetic anomalies. These anomalies can also be produced by any other electronic gear you have on your person, e.g. a camera or even the battery in your car-keys. Also, it's very difficult to do this anyway, given how small and unstable these things are. A "near as damn it" attitude will leave you close to swearing later.

Basically you need to use a GPS device and take care to get the best accuracy you can get. You start by taking a waypoint at the centre of the stone circle (or whatever). You then need to look for distinguishable features which are on the line of the horizon, go and visit them, and take waypoints at those locations too.

The further away these horizon features are (from the central point), the better.

When you plug these waypoints into your GPS software on your PC, you will be able to derive the angles between your central point and the horizon points to the nearest degree, using the software.

When you come to construct your landscape and play with it under Stellarium, you can click on one of the horizon points, which, more likely than not, will select some star or other feature. The readings at the top left of the screen will tell you the Azimuth of the star, which will be the same as the azimuth of your horizon feature. This should be the same as the angle-from-true-north that you found for that horizon-point from the central-point that you previously discovered from your GPS software.

Don't assume that all your software(s) or other sources of information measure Azimuth in the same way. Somtimes it's taken from North, sometimes from South etc. so you need to compensate if they're different.

Ian

[Ian Pegler]

1) Don't use a compass.
2) Read tip no 1 again. Really, don't use a compass.

See also my comments on the Mitchell's Fold thread.

Ian

[Ian Pegler]

I recently downloaded version 0.10.2 of Stellarium and it is soooooo much better.

The graphics run faster, the date/time window is more stable. What a relief. If only they'd released this a couple of weeks ago, my life would have been much simpler.

Ian

[Ian Pegler]

Location, Location, LOCATION !!!

How many times have I been tripped up by this one...

When you load up Stellarium the landscape may not match the location. So for example, you may be looking at Mitchell's Fold, but in the bottom left corner, the location may read "Paris" or somewhere else.

With 0.10.2, you can go into the landscape-selection and click the one you want. This will then move the location accordingly and the text at the bottom left should change accordingly. Even if the one you want is already highlighted, click it again - the location changes, and you see the positions of the stars etc. move around.

So always check that the text at the bottom left of the main window matches where you want to be.

Another way of doing this is from the Location window but I prefer to do it from the Landscape page because it can deal with both simultaneously. You should tick the box marked "Use the location associated with this image".

Ian

[Grahame]

You should tick the box marked "Use the location associated with this image".

I think you'll find it says "Use associated planet and position" - at least it does in my version of 0.10.2..!

**edit - I just discovered Scripts! In the configuration window (F2), click on the 'Scripts' tab and pick one to try. The first one does a tour of your installed landscapes, but Ian will be more interested in the one that simulates this year's solar eclipse. It works much better than previous versions.
I did find that a couple of the scripts caused Stellarium to lock up, so these are still a little bit buggy. But very effective for all that.

[Ian Pegler]

So it does.

I recently found a neat little solar eclipse which was visible from this country in the Middle Ages. This was at around 2pm on October 29th in 878 - the year King Alfred burned the cakes !! The "path of totality" came directly over the UK and also, the point of greatest totality was directly over the U.K. which is very rare. If you run Stellarium with this command line:

C:\Program Files\Stellarium\stellarium.exe" --sky-date 08781029 --sky-time 13:59:59

... you'll see it. Certainly visible at Mitchell's Fold, the shadow is unmistakable.

Ian

[Ian Pegler]

Ian will be more interested in the one that simulates this year's solar eclipse

Yup, I had already discovered that one. What a corker!

Ian

[Ian Pegler]

Brilliant idea, Ian. Now who do we know who lives near Avebury and has a camera.....?

Rory...?

Hi Kevin
Yes I live near Avebury.

from here



Ian