I think the trajectories from there are nowhere as good as Baikonur

Baikonur is 45.62° N, 63.31° E

Vostochny Cosmodrome, (Tsiolkovsky, Amur Oblast) is 51.85° N, 128.35° E. 550 miles west of Sakhalin Island and the Sea of Japan.

51° N is like London...not the best latitude for launching to space

It's definitely not optimal, but GP probably wanted to highlight that it's not much worse than Baikonur (45°), at least when you compare it to Cape Canaveral (28°) or Kourou (5°).

Yeah, most of the continental US is better than 45°.

Got to love those dog-leg manouevres and a dashing of extra fuel :)

I don't know anything about space launches, how come the first orbital launch site in mainland Europe is in Esrange in northern Sweden, latitude 67° N? Are different latitudes good for different trajectories?

Yes, Esrange is best suited to launches into Sun Synchronous Orbit, which is high-inclination (nearly a polar orbit). It's very popular for things like Earth observation satellites.

To clarify, SSO is very popular.

You’re right. 45.6deg vs 51.8deg N.

The eastward boost you get from the earths rotation is just: 2 * pi * cos(latitude)/day so the difference is: 2 * pi * r_Earth*(cos(45.2deg)-cos(51.8deg))/day = 40m/s.

Which doesn’t sound like a lot but can add up.

I never considered this and your response made me ask google the question: "Where is the best place to launch a vehicle?"

"The land at the equator is moving 1670 km per hour, and land halfway to the pole is only moving 1180 km per hour, so launching from the equator makes the spacecraft move almost 500 km/hour faster once it is launched."

Neat, thanks for such an interesting answer.

wondering if there is an inhabited planet somewhere out there much more optimized for launching spacecraft

with its equatorial denizens barely hanging on to its surface

Size and mass are the other big factors.

Kourou, at 5° North, is very nicely positioned.

Yeah it's no accident SpaceX built their test launch facility on the beach in Texas, less than 10 miles from the southernmost point in Texas. Brownsville is about 20 miles away and is a natural, true deepwater port which is also helpful, but primary reason was to get as close to the equator as possible while still being on the US mainland. You can throw about 9% more mass into orbit on the equator than from NYC. Florida coastal property is mostly built out and southern Texas is mostly vacant + has a very favorable business climate and lax (state-level) environmental regulations which doesn't hurt either.