Deleted

Magnetic ballasts that can run two >20W lamps in series, are limited to the american HPF rapidstarts only. Even the american preheater can't operate two >20W lamps in series.
Otherwise, you are limited with an electronic ballast.

Deleted

Unfortunately, it is not possible to put 2x TL-D 58W in series; the combined arc voltage is too high for a 220-240V mains. Putting them in parallel won't work either: once one tube is on, the other will not be able to come on as well.

The voltage of a 58w tube is about 107v iirc. For 2 of them it would be 214v - Way too close to the 240v mains and not reachable even with CSS circuit. If you have 415V (from 2 phases) however, you may try the 2 tubes in series with 2 58w ballasts in series (this would underdrive them a bit so you can experiment then with replacing 1 of the 58w balast to a HID ballast), and use S10 starters

You may try running them in series with a single "58W" ballast and a 7.5..8uF/350VAC capacitor (the exact value you have to try) - that could provide just enough conditions to run the lamps.
But do not expect much from that - if it would work at all, it would be just marginal with 240V mains.
The maximum I successfully tried was a 170V lamp on 230V mains, yours would be ~215V, so way less margin...
For starting you would have to use manual switches, there is no starter available for such configuration (the regular concept won't work)

Deleted

Deleted

Since the startng voltage of the arc is higher than its holding voltage, as soon as 1 lamp strikes it will keep the voltage to its arc voltage, adn effectively ensure that the other lamp cant strike. I think all you'll get is both lamps flashing in startup, then  1 lamp light up at 2x the current and 1 lamp remain off

Deleted

Deleted

How about 8 8ft T12 lamps + 9 2x8ft fixtures (including ballasts), 20km from home (out of which bus path is 1km short), all that in 3 rides ? My experience : possible but you crash down on the doorstep

the problem is the OCV is too low, parallel wiring the ballast only gives you more current

however our RS HO ballasts here in the US are series even for 8FT lamps, they have 500+ OCV and usually 750-1,000V for slimline ballasts

Only with preheating transformer they won't ignite, you would need a starter/ignitor anyway.
And I do not see a possibility to easily combine the starter and transformer so, the starter won't ignite the lamp with electrodes not yet warmed up...

The best would be to wire the lamps into the regular preheat circuit and for long cycle life, use an electronic starter (S10e from  Philips,...)

Modify a HID ignitor to wait before it starts pulsing ? (capacitor+diode clamping down some control voltage for a while untill it charges etc. 2nd diode and resistor to discharge it if power disconnected)