dish declination setting

This is tricky as dish I have to set up has no info on model or manufacturer as with motor . Latitude here 53 degrees approx hence motor elevation approx 37 degrees. But how can I calculate the dish decination from the motor arm for the dish?

Just awkward to adjust as on large p[ole in the garden which unfortunately has to be taken down for adjustments. An absolute nightmare really but position of the house would obscure all sats from 28degrees to any further sats west. Only other option woud be a chimney installation as other houses would block many sata if even put very high on the face of the house.