I told a guy I know I'd ask about his ballast. He can't figure out how to wire it, but here's what he knows:

It's made by atlas. It has four wires labeled P, APU, 230V, and 240V. It is a 250W pulse start metal halide ballast. The values for the cap have been eroded from the sticker. The ignitor has three wires labeled neutral, live, and out.

Thanks

The capacitor is there most likely only as PF correction, so it's value would not be as critical.
I do not know exactly this ballast, but i think i might help you, if you support me:
- Take Ohm-meter and by measuring resistances determine, how the winding pass via different terminals, determine winding ends.
- Connect ends to an output of some 12..48V transformer (better to handle with safe voltage only, if it is not really necessary otherwise) and measure voltages on each section. If you do not have such transformer, connect ends in series with ~100..200W incandescent lamp (to limit the current), but then work very carefully, as voltages become dangerous.

And send results (post here and/or PM me...)

All readings are in DC ohms:

P-APU 0.1
P-230 1.9
P-240 1.9
APU-230 1.6
APU-240 1.7
230-240 0.1

Do you know more about the ignitor?
And what is the voltage ratio between sections (P-APU):(APU-230)?

There are two options:
1) The ignitor is of 200V pulser (like on fig9.12 on page 5). Then it need the ratio 1:20 (so ignition voltage would be 200V*20=4kV), connection would be:
- "230" or "240" live input (depend, what is closer to actual average mains voltage on the installation place)
- "APU" is connected to the ignitor output
- "P" is output to the lamp, at the same time connected to ignitor "live".

2) The ignitor is equivalent to Philips SN57 (long range 800V semiparallel pulser), then the ratio would be about 1:5 (so ignition voltage would be 800V*5=4kV), connection would be:
- "P" is line input
- "APU" is connection to the ignitor output
- "230" or "240" lamp output (depend, what is closer to actual average mains voltage on the installation place), ignitor  "live" is connected here.

What might help also: If some terminals are clearly of higher voltage construction, these would be more likely on the lamp side.

I told him to try option one and he said it works great, so thanks for your help!