The march will be held in Edinburgh on 13 September, five days before the Scottish people go to the polls to decide whether the country should remain in the UK or become independent.A spokesman from the Grand Orange Lodge of Scotland said up to 15,000 people are set to take part in the demonstration, including a large number from NI.Grand Master of the Orange Lodge in Ireland Edward Stevenson is also expected to attend, alongside his counterparts in Scotland and England, and other senior Orangemen.It has been described as one of the largest gatherings of the Order in recent times.While the Orange Order is an official supporter of the pro-union Better Together movement, a spokesperson from Better Together stressed that the organisation "is not part" of it.This organisation is not part of our campaign and never will beBetter TogetherHowever the Scottish Grand Master, Henry Dunbar, has said the organisation is very proud of the role it has played in supporting the union."The Orange Order in Scotland is justly proud of our British Together campaign," he said, in an interview with the Order's Orange Standard newspaper."It has energised our members and earned us many plaudits and admirers outside the Institution."The referendum on Scottish independence will be held on 18 September when voters will be asked to answer the yes/no question: "Should Scotland be an independent country?"Scottish First Minister Alex Salmond and his SNP government are leading the 'yes' campaign, while the main opposition parties argue Scotland would be better off remaining in the UK.Interviewing Scottish First minister Alex Salmond today in Glasgow he tells me NI has nothing to fear from a yes vote— Tracey Magee (@Tracey_utv) September 4, 2014According to the latest YouGov polls, the 'no' side's lead has recently collapsed to just six points on 53% while the 'yes' side is now close behind on 47% - not accounting for undecided voters.It comes after the second of two televised debates between Alex Salmond and Better Together leader Alastair Darling, which took place at the end of August.There has also been some speculation that the Orange Order's upcoming parade could serve to alienate Catholic support for the union ahead of the referendum.Scottish Grand Master Henry Dunbar said he believes the day will be a success."We anticipate a hugely effective rally in Edinburgh on 13 September," he continued. "It will be the climax of our campaign, a massive celebration of pride in the United Kingdom."We hope it will be instrumental in delivering a resounding victory for the Union over Alex Salmond and his misguided separatists."