Alignment of my hybrid Ultima 2000

I have an celestron Ultima 2000 mount which I have mated to a Celestron C-8 OTA which was not originally an Ultima 2000. It does not have the "downstop" on the end of the telescope tube.
Is there a way that I can accurately set the scope to the downstop position for alignment purposes with the downstop not being present. I was thinking that perhaps a bubble level indicating true vertical of the OTA might be a possible answer.

Any suggestions are greatly appreciated on how I might get a good alignment without benefit of a downstop on the OTA tube.

Thanks,

Gene Middleton

:S

Prior to GoTo computers, mounts were manually aligned. How-To instructions can be found in older Amatuer Astronomy or Telescope Making books available from your local Public Libary.