Patience is a virtue, points out Morgan Stanley as it keeps its 'overweight' rating and 1,500p target price on oil explorer Tullow.The broker said that in April, Tullow should provide investors with some clarity in on the recent purchase of some Uganda assets. Tullow Oil said in January that it has agreed to buy Heritage Oil's assets in Uganda for up to $1.5bn.Morgan Stanley thinks that ownership of the assets will support increased production at Tullow.