Rick's b.log - entry 2025/06/09

Notebook battery

Enjoying the enjoyable weather.

Custom landscapes for Stellarium [tutorial]

Here's how.

Taking the image

Making the photo sphere.

I would advise two things. Firstly start from a definite cardinal point, this will make things easier later on. And secondly, go around horizontally, and then do so again in levels going up until the sky has been fully captured. This is because accuracy can drift a little the more photos you take and for our purposes the skyline is important, the ground is not, so leave that until last.
If you are really struggling, then stop and rapidly move your phone in a three-dimensional figure eight motion to wake up the compass and movement sensors. You'll probably be aware of this if you have ever used the Sky Map app.

Eventually you will end up with a weird looking photo panorama that's like this.

The finished product.

This is called an equirectangular picture. This provides the best quality as the centre line is hardly distorted, the main distortion happens straight up and straight down, neither of which tend to be especially important in 360° images.
A common alternative is a fish-eye sphere, where straight up is in the middle and everything else is distorted, often greatly.

Transfer this image to your computer using whatever process suits you. I used Bluetooth.

Preparing the image

The first thing to do is to reduce the image because you don't need to tax your machine when it is running Stellarium. Scale down to 2048×1024 and set the DPI to traditional monitor quality which is 72 dpi (this is only informational really).
If you are using Gimp, the menu option is Image → Scale image...

Once you have done that, add an Alpha Channel to your photo. This will permit it to support the use of transparent. If you are using Gimp, the menu option is Layer → Transparency → Add Alpha Channel

Now select the magic wand tool ("Select by colour" in Gimp) and click on the sky. You'll see a section of sky highlighted, but probably not all of it. You'll want to do whatever is necessary to add to the current select. This may be a little '+' button. Or it may be like in Gimp where you hold Shift and just keep clicking to merge the new areas into the already selected.

You may find that you need to tidy up because selection is imperfect. Play around with the other tools to see how best to do this. In Gimp under the mask preview on the right (that odd black and white display) there's a little icon that's like a circle in a square with the shading reversed. This is the "invert selection" button, so you can add to the sky (to expand) or add to the ground (to reduce). If you cannot find this icon, you can also use the menu, under Select → Invert

You can also use the freehand selection tool (the lassoo). Click while holding Shift and keep on going until you get back to the start.Double-click to close. Then press Enter to accept that. If you find it isn't working, you probably forgot to press Enter. Ask me how I know. ☺

I would recommend, with the sky selected, growing the mask by a pixel in order to reduce the jarring contrast between the photo and the sky that Stellarium renders. In Gimp the menu is Select → Grow...

You'll see something sort of like this.

The mask set up as desired.

What happens next may depend upon your software. You will want the sky to be the part that is replaced, and often the masked area is that which is protected. In Gimp you'll want the sky part in the diagram on the right to be shown in black, not white. Invert the selection if this is not the case.

Now you will want to switch out that area, the sky, for the other layer, the transparency. With Gimp this is a two step process. Go to the menu and use Layer → Mask → Add Layer Mask... and then set the layer option to Selection. Do not pick the Alpha channel setting.
What you have done is to take the area that was marked as selected and initialise the layer (the transparency channel that you created at the beginning) to be the same as the selection. This effectively renders all of the pixels of the selection invisible.
We do it this way, rather than trying to use the selection tool to apply transparency directly, because this is binary. Pixels are either visible or invisible and not partially visible. This is what we want.

Here's the result.

The mask changed to transparency.

Now save this image as a PNG image. If you are given options (Gimp does), turn off everything except the use of background colour. You don't need annotations, colour profiles, resolution/dpi information, or any of that rubbish.

The image has now been prepared. Note that you can use a process broadly similar to replace one sky with another in your own images, like washed-out white with lovely blue (if your camera doesn't support HDR). For this, you'll probably want to use a different image as a layer rather than transparent; or maybe cut out the ground and paste it on top of a sky. You may also want to play around with Feathering, that is to say making the edge pixels slightly masked in order to blend them into the sky and make a more natural result. Feathering wasn't used here as we only want pixels to show or to not show.

Preparing Stellarium

Now go into landscapes and create a new folder for your own landscape. It doesn't matter what you call it, but something appropriate is better than cthulhu.

Now create a file called landscape.ini and give it the following contents:

[landscape]

name = Display name here
author = Your name
description = A description.
type = spherical
maptex = ImageName.png
angle_rotatez = 179

[location]

planet = Earth
latitude = +51d08'40"
longitude = +2d41'55"
altitude = 34

You should set the name, author, description, and maptex fields as appropriate.

It seems as if west is zero degrees, which is odd as I'd have expected north. So if your image centre point (where you started) is:

West - use 0
East - use 180
North - use 90
South - use -90

Finally, set the latitude, longitude, and elevation as applicable. The values given here are for Glastonbury Tor.

Note that it expects Degrees,Minutes,Seconds. If you determine your location using Google Maps it will give you Decimal Degrees (a number with a fraction). You'll need to do some maths or use a third party website to change DD to DMS.

When done, save the file and load Stellarium.

Loading your landscape

Choosing a landscape.

When done, you can see your own stargazing locations in Stellarium.

Looking north-east.

Looking east from the west.

If you find the alignment is slightly wrong, you will need to fiddle with the angle_rotatez in the landscape.ini file. Unfortunately it appears as if Stellarium caches the contents of these files, so changing them will require a quit and reload which... isn't fast. Luckily it should only need to be done a few times to get everything set up just right.

My happy word

The word is:

Yeah, I'm weird...I know.

Winning Euromillions

I did a quick calculation. Assuming I can bank it at a place that'll offer me 4% interest, which is a tad on the low side for "Big Money" but reasonable enough, I could expect to make €10,000,000 per year in interest.
If it is banked here in France, the government will want to claim about 65% in wealh tax. This leaves me only (!) €3,500,000 per year.

Which is about €67,300 per week.

Or about €9,600 per day.

So sitting on my arse doing absolutely nothing for a two and a bit days will make me what I get working my arse off for 1,607 hours in a year (that's about 46 and a bit weeks of 35 hours, a typical work year).

New septic tank? Three days of saving ought to cover it.
New driveway? Ditto.
Maybe three days to sort out the old electrics and the plumbing.

And so on, for a month, or about a third of a million euros. At which point I think everything will have been organised, the grounds tidied, and... then what? There are some places I'd like to visit, but as a regular introvert on holiday and some somebody who has a private jet and stays in hotels with gold plated taps. I'm sorry, I'm just not interested in that sort of thing. Nor am I interested in buying a fancy sports car. I live rural, low-slung sporty things with stupidly thin tyres are just not practicable here.

It would be nice to win enough that I can get work done here, and maybe think about retiring comfortably. But quarter of a billion? That's stupid money, that is. Just think have many lives could be changed if they picked ten people and gave them a two and a half million each. Life changing money without being life ruining.

I won the lottery on Friday. But I don't think I can retire for €10,20. ☺

Your comments:

Please note that while I check this page every so often, I am not able to control what users write; therefore I disclaim all liability for unpleasant and/or infringing and/or defamatory material. Undesired content will be removed as soon as it is noticed. By leaving a comment, you agree not to post material that is illegal or in bad taste, and you should be aware that the time and your IP address are both recorded, should it be necessary to find out who you are. Oh, and don't bother trying to inline HTML. I'm not that stupid! ☺
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A tree-dwelling mammal, 10th June 2025, 08:58

I still think the best word of the day is 'cockwomble'. Anyway...    When I saw the "Winning Euromillions" heading I thought you'd won Euromillions. Meaning you could afford a trip to the UK for the next RISC OS show. Oh well.

C Ferris, 10th June 2025, 13:47

Have you tried ROX Linux front end.

C Ferris, 10th June 2025, 13:54

At the Royal Cornwall Show - a firm had a demo of their Septic Tank - about the size of your Bubble Car - requires about 80 watt power - outputs clean water that can be dumped into a local stream - and quano to be collected once a year.

jgh, 11th June 2025, 02:19

Bolleaux to chucking away cleaned up water, that's my water, I've paid for it! I'd pump it up into my toilet flushing storage tank. If it's clean enough to dump in a river, it's probably clean enough for the washing machine as well.    This is my Hong Kong experience rubbing through. "Use *drinking* water to flush the bog? Are you mad?" We had two supplies, drinking water, and flushing water which was filtered sea water.

C Ferris, 11th June 2025, 08:33

Rick could always use Aus style Long Drop toilet:-)

Rick, 11th June 2025, 18:05

I have one of those outside. It's the breezeblock thing at the end of the pig barn opposite the house with the blue plastic sheet covering the doorway...that I try to hide in photos.    But this is France. If I actually used it, it would need to be emptied at intervals and I'd need to demonstrate this with *all* of the requisite documents.  Do *not* underestimate the French obsession for paperwork. It's a thing that even drives the natives batty.

C Ferris, 11th June 2025, 18:32

Your potato's should do really well :))

P, 21st June 2025, 02:01

"Unfortunately it appears as if Stellarium caches the contents of these files, so changing them will require a quit and reload which... isn't fast. Luckily it should only need to be done a few times to get everything set up just right."    → If you reload landscapes frequently, try editing the config.ini to turn off caching:  [landscape]  cache_size_mb = 0

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