This seems MUCH more difficult than it should be - making good observations with a common DSLR camera. The problem appears to be getting a time within a tenth of a second.
The camera that I am using (which appears to be comparable to newer cameras) is the Nikon D200, which apparently records several times, all to a couple of decimal places of accuracy. But to set the camera you can only do it by hand - and I bet that it is not routinely possible to set the camera correctly to a tenth of a second. That makes us wonder why the camera can record to an accuracy that will never be reliable! The camera has a GPS connection but the GPS time is kept separately from the camera time - why does the camera not set it’s internal time from GPS!
I have talked to a couple of sources of drivers for cameras (latest one was AstroDSLR by Peter Polakovic).
Could people answer here with: what DSLR are you using? What drivers? Does anyone know of any DSLRs that set time from GPS?
Several people have talked about latency, USB saturation, etc but it seems that a tenth of a second should be something that a camera could reliably record.
I am currently using a Nikon D200 (older camera) and the provided control software but am going to try some of the available drivers in the next week or so. The camera records GPS time to the second only.