Well, the cat is out of the bag. It is indeed inspired by the Nebra sky disc. There was a clue all along for anyone that opened any of the photos in another window, or downloaded - they're all called "NSD nn.jpg".
Some background rambling on where the idea came from... It all started with a sewing machine. When I picked up an old Singer recently, and got back into some sewing, I started planning a satchel (which is still being designed in my head). That led to me thinking about what I might put in it, which led to a bit of abstraction about old school gear, which included an 'ancient artifact'. I went to eBay to find one (obviously), but wasn't impressed with most of the Egyptian things (mostly painted resin castings, some that were too delicate for a satchel, like boats with bits sticking out, and some that were too big). I was after something that would survive a bit of rough and tumble in the satchel after I had been out on an artifact looting expedition.
I then looked at stuff that was a bit more obscure, like obsidian pyramids and various crystals, but they were mostly too small and maybe wouldn't come out clearly in a photo. I've been aware of the Nebra disc for a few years, and the idea to make one was probably a result of a separate activity - I have an occasional interest in ancient astronomy, and when the disc came to my attention again, I decided that it would be my ancient artifact.
I'm not trying to make an exact copy, but I do want something that's pretty close. I had originally planned to make it 8" in diameter so that it would easily go into the satchel, but ended up making it 10" on the basis that it has to have a life beyond the satchel thing - it will end up as an artistic piece that will hang on the wall. (The original is about 12.5", which is a bit big for the satchel.) I then looked into metals, and eventually settled on brass. I struggled a bit to find bronze (the original material) at reasonable prices, and copper would be just a bit too soft. I also looked into gold sheet but quickly stopped when I worked out it would be very expensive. Brass polishes up very well and can look close to gold, so thin brass sheet was chosen for the applied shapes.
To get the shapes and positions close, I made a tracing of a photo of the disc in CAD software. The picture below has the image of the disc darkened so that the CAD drawing shows up more clearly...
This started by importing the image and resizing it so that the disc was 320mm across (the size of the original). I then added the shapes by drawing on a separate layer, before copying the layout without the image to a separate area. This gave me a 1:1 scale drawing of the main features, and it was then straightforward to resize this to whatever I wanted. With the eventual size decided, it's easy to make the applied shapes the right size of the new disc. The original stars are 10mm, mine are 8mm, and the other shapes are derived from a printed 1:1 template at the new size.
Those that are familiar with the original may be aware of a few details relating to bits missing and changes made during its development. I won't be sticking exactly to these details. For example, I'll obviously have both of the long gold arcs because I've made both of them. A more subtle change I'm making is the angle created when you draw a pair of crossed lines from the ends of the arcs. On the original, the angle is 84°, which happens to be just about the angle between the summer and winter solstice sun rises and sets at the disc's latitude of 51°N. I'm very close to 56°N, and the solsticial range here is about 89°, so my disk will be 'calibrated' for my latitude - my arcs are proportionately longer than those in the original.
Something I'm a bit undecided on yet is simulating the damage. On the one hand, I don't want it to look too perfect, but I'm wary of making damage that doesn't look convincing. Anyone that plays electric guitar will likely be aware of so-called 'relic' finishes, where a guitar is artificially aged to make it look like it's been used for years. They're notoriously difficult to do well, and are often over the top. I'm aware of this, so will likely take my time to see what I can do to add some light damage. At the moment, I'm aiming for something that looks like it's from the same source or maker, looks old, maybe has some light damage, but is in better overall condition.
I won't go into details on how things will proceed from here, partly because I don't know if what I have planned will work (I'm still experimenting with some bits as I go), and partly because I like the idea of revealing each stage as it happens. At least photographing some the of the subsequent stages will be easier - I was expecting to have to stick to close-ups to avoid showing the whole disc once the bits were applied in case it gave the game away until the end.
More to come...