Swinside and Sighthill in Stellarium

I’ve just made two new stone circle landscapes for Stellarium, the free planetarium software. It’s been quite a while since I created a Stellarium landscape, and I’d forgotten quite how much fiddling around was involved. It does become quite time-consuming, but it’s very satisfying when you do get it to work. This time round, I used two programs that I hadn’t used before, and I actually found the process much easier than previous attempts.

There are two main parts to making a landscape – the first is to create a panoramic image from a series of photographs taken from the centre of the site. I mostly make what’s known as a ‘spherical panorama’ as this is by far the easiest landscape to create. It requires a 2:1 landscape picture with the horizon line centred vertically. The easiest method is to make left-hand edge of the picture the due East position in your landscape, and this is the method I mostly use, although it’s not the most accurate.

In previous landscapes, I used a proprietary panorama-stitching program that came with my Canon camera, but it’s too outdated to run on my PC these days, so I downloaded a freeware program, the Image Composite Editor from Microsoft Research, which was simplicity itself to use, and automatically stitched together the 12 or so images perfectly without requiring any adjustments from me. This particular package has a huge advantage in that it allows you slide the image left and right during the process so that it is extremely easy to get the East point lined up with the left-hand edge of the picture. The alternative method for aligning landscapes, and the more accurate one, is to create a GPS waypoint in the centre of the circle, and another at a distant landscape feature that is visible from the site. Using any GPS software, you can then calculate the azimuth of this baseline and by means of a simple calculation, work out an angle of rotation that you insert into the Stellarium landscape.ini file. I won’t explain this further here, you can find details on the Stellarium Wiki pages.

So now we have a narrow landscape panorama that we have cropped to a roughly rectangular image, with the left-hand edge being east. The next stage is to load this into a paint package and create our final image. Export the file from ICE as a .png file, making sure to check the ‘include alpha channel’ option as we need to make parts of the image transparent. I used to do this in GIMP, another free program; but it’s not the most intuitive beast to use for this and has way more features than we require. This time I used the freeware Paint.net, which I found much easier to use. The basic program is fine for this particular purpose, but you can also download a ton of effect plugins to make it more versatile from the Paint.net forums.
NOTE: only download add-ins from the official forum as the internet is rife with virus-laden fake plugins for Paint.net!

Adjust the size of the image to create the 2:1 ratio – I use 4096 x 2048 pixels. You may need to move the image vertically so that the horizon line is exactly centred horizontally (this is assuming that your real-world site has a level horizon of course – if not, you will need to adjust things accordingly). Now we need to make all the sky area transparent so that the stars will show through in Stellarium. If your panorama skyline is relatively free of obstructions, this is generally a simple process of selecting the sky using the ‘magic wand’ tool in your paint package, then deleting it. If the skyline is more complex, particularly if it involves trees, you often have to spend a long time with a small eraser brush manually deleting parts to make them transparent. This is probably the most tedious procedure, but persevere with the fine detail as it will pay dividends in the finished landscape.
So now we have a transparent sky, and our panorama image – but what about all that blank space at the bottom? Well, the short answer is that we cheat. In the case of a stone circle where the ground is usually grass, it’s a simple matter to make a brush from a part of the existing image and use that to paint grass over the rest of the image. You can use the clone brush to do this fairly quickly. One important tip is to make sure the left and right edges of the image have matching texture, otherwise you will have a very obvious join line in the final landscape.

After finishing the panorama, we create a landscape.ini file, which is a text file that tells Stellarium what the landscape is, containing some information about the site, together with a few technical details including the latitude, longitude and elevation of the site. Usually a readme.txt file is also created giving instructions on how to install the landscape, and all three files are then saved as a zipped folder. Again, you can find instructions for this on the Stellarium Wiki pages.

These latest landscapes that I made are of Swinside (aka Sunkenkirk) stone circle in Cumbria. I did actually create a GPS baseline for this at the time I took the photographs, but I subsequently found it easier to base the east point on the Alexander Thom survey of the site that I found online. There’s also a handy tall stone pointer marking the North in this circle, so it wasn’t too hard to confirm once I had created the landscape and loaded it up in Stellarium. Here’s the winter solstice sunrise from the circle:

Swinside winter solstice sunrise

For an encore, I revisited one of my early landscapes, the Sighthill stone circle in Glasgow. I wasn’t very happy with this landscape as I’d taken the pictures some time ago with my old digital camera, which was pretty low-resolution by today’s standards. Also, there have been quite a few demolitions of tower blocks and other buildings since then, so the skyline has changed substantially over the years. I took a new set of pictures for a panorama a couple of years back, but what really motivated me to get this update finished is the forthcoming northern minor standstill of the moon on Dec. 25, when the moon is full, which is one of the alignments that the circle was intended to mark. As Glasgow City Council have plans to redevelop the Sighthill park area with new housing, this is quite probably the last chance to see this standstill alignment from the existing site. Although the Council have promised to retain the stones and re-erect them at another location in the vicinity, it seems highly unlikely that the circle will enjoy the splendid views that it currently has, so in future this Stellarium landscape may also act as a memorial to how it used to look. Here’s how the predicted moonset over the northern standstill marker stone at 08:05 on the morning of Dec. 26, 2015 should look, weather permitting of course:

Sighthill N-standstill moonset

Click HERE to download both these landscapes, and a collection of other fine UK sacred site Stellarium landscapes.
For the complete worldwide collection of landscapes, visit the Stellarium landscapes page.

Grahame Gardner
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