Glasgow-based photographer Craig Mann, whose work usually features landscapes from around the world, used Photoshop to make the pictures.
They feature characters such as Princess Leia, Darth Vader, bounty hunter Boba Fett and Ewoks.
The firth is used for anchoring rigs during winter and downtime from work.
Mr Mann, who is from Shetland and now lives in Glasgow, works on the rigs and created his Star Wars collection of photographs in his free time.

It comes after a jury concluded the death of a man from St Austell was suicide, while undergoing care 140 miles from where he lived.
David Knight was killed by a train near St Austell after going on leave from a Somerset hospital.
The Department of Health has admitted "unacceptable" patients "are receiving care far from home".
Click here for live updates on this story
BBS South West Political Reporter Tamsin Melville said county coroner Dr Emma Carlyon was understood to be satisfied there was a commitment locally to continue to work hard to ensure the lowest number of patients possible leave the county for treatment.
An inquest in June heard that in May last year Mr Knight died of multiple injuries when he was hit by a train on the viaduct.
The 29-year-old had been suffering from paranoid schizophrenia when he died.
A jury said his death was contributed to by an inadequate risk assessment and support while he was on leave from Cygnet Hospital in Kewstoke, Somerset.
The inquest heard Mr Knight was being treated there because there were no acute psychiatric inpatient beds available in Cornwall.
The NHS said 30 adult mental patients were placed out of Cornwall in 2015/16, 150 the year before when a key unit was closed for six months, and 60 the year before that.
The Department of Health said it had increased mental health funding to Â£11.7bn and had accepted the recommendation of the Mental Health Taskforce that the inappropriate use of out of area treatments for adults in acute care "must be eliminated by 2020/21".
"We will work to a faster timetable if at all possible," said a spokeswoman.
"We will consider Dr Carlyon's letter in detail once it arrives."

Former Newmarket Town player Shaun Whiter lost both his legs when he was hit helping his friend Joey Abbs to change a tyre near the Suffolk town. Abbs suffered a serious leg injury.
Cambridge United will host a Football Family Day on 9 October to raise funds.
Messi's shirt and one from team-mate Arda Turan will be auctioned off.
Wayne Rooney and John Terry have also donated signed shirts, as well as the first teams of Liverpool, Tottenham, Chelsea and West Ham, and the England senior squad.
Newmarket Town, Soham Town Rangers, Cambridge City and Fulbourn Institute - teams for whom the pair played - will take part in a mini-tournament at the League Two club's stadium as one of a number of activities on the day.
"I can't thank Lionel Messi and Arda Turan enough for donating their shirts and getting them to Cambridge," Whiter told BBC Look East.
"We're going to auction them off and see what we can get."
Jan Adamec, 40, from Haverhill, pleaded guilty to two charges of causing injury by dangerous driving and was jailed earlier this month for three years and four months.
And Whiter, who has previously said he would like to compete at the 2020 Paralympics, spoke of the bond between him and Abbs following the incident.
"He's a great friend. I've asked him to be one of the ushers at my wedding next year. He made that call that night to the paramedics to save my life," he added.
"He saved my life and I can't repay him any more than with my friendship and support him through this time as well."
A photographer has created images that place some of Star Wars' best-loved characters on oil rigs parked up in the Cromarty Firth in the Highlands.
[NEXT_CONCEPT]
Cornwall's coroner will raise concerns with the health secretary over the care of mentally ill patients far from home.
[NEXT_CONCEPT]
Barcelona's Lionel Messi has donated a signed shirt to raise funds for two former non-league footballers who were victims of a hit-and-run driver.