I would like the camera to fire a remote flash. I guess what I am trying to
do is make the sb-27 behave like a remote sb 600 or 800. This means
connecting the 1995 technology to the dSLR technolgy. If I understand
correctly, a su-4 or one the third party equivalents will do the job.
Is this correct?
Yes and no. You can make it work remotely as probably described in the SB-27 manual (but not in TTL mode), with third pary slave trigger too, but you cannot make it work with the Nikon CLS system described in the D70 manual.
There are two ways to do "wireless" remote flash with the D70.
One way is the Nikon CLS system described in the D70 manual, but which only works with new flash models designed for it, SB-800, SB-600, SB-400, SB-R200. The D70 internal flash menu is set to Commander mode and these external flashes are set to their Remote mode. By a system of preflashes, the camera meters a test preflash from the remote flashes and then fires them for the shutter exposure. The older flash cannot do this.
But you can put the D70 internal flash into its Manual mode and it will fire any older flash that is equipped with an optical slave trigger. You just need an optical slave trigger, such as the Nikon SU-4, but there are several others. It should have a hot-shoe to hold the SB-27, and then it will fire the SB-27 when it sees another flash, such as the D70 flash in manual mode. (or of course, you could add the Nikon AS-15 hot shoe PC cord connector and use a PC cord to the flash, if the flash unit has a PC connector. This is Manual mode too).
Note: If you attempt to use D70 internal flash in its iTTL mode or Commander mode, then it will NOT work with the older flash, because the preflash will trigger the external remote flash trigger before the shutter opens, and you get nothing. The D70 must be in Manual flash mode.
The external flash must be in either Manual mode or its own Auto mode. Auto uses the sensor in the flash unit to attempt to meter the subject and flash. Manual means you meter it yourself, like with a handheld flash meter.