Peggy,
The Elizabeth Watson who died on 21.2.1885 at Tirnaskea was a farmer’s widow. The informant was her son William.
https://civilrecords.irishgenealogy.ie/churchrecords/images/deaths_returns/deaths_1885/06291/4802851.pdf
She died intestate, but helpfully the probate abstract links her to Tamnaskinney:
Letters of Administration of the personal estate of Elizabeth Watson late of Tamnaskinney County Tyrone Widow who died 21 February 1885 at same place were granted at Armagh to George Watson of Tullyreavy in said County Farmer the Son. This is George with his sister Ellen in 1901:
http://www.census.nationalarchives.ie/pages/1901/Tyrone/Oaklands/Tullyreavy/1729359/
Then there’s this abstract:
Letters of Administration of the personal estate of John Watson late of Tamnaskinney County Tyrone Farmer who died 3 March 1880 at same place were granted at Armagh to George Watson of Tullyreavy in said County Farmer a Son. John was 76 when he died, so born c 1804.
John had 4 pieces of land in Tamnaskeeny (plots 1, 11,12 & 25). According to the Valuation Revision records, after his death they pass first to Eliza and then to George and then to Rev John Watson. This may be the Rev John in 1901:
http://www.census.nationalarchives.ie/pages/1901/Armagh/Charlemont/Keen…
I noted this additional Watson farm in the townland, who could perhaps be their son Henry:
Probate of the Will of Henry Watson late of Tamnaskinney County Tyrone Farmer who died 10 February 1900 granted at Armagh to The Reverend Thomas S. Watson Clerk
The will itself is on-line on the PRONI site and mentions his son the Rev Thomas Stewart Watson of Clough Glebe, Fermanagh, This looks to be him in 1901:
http://www.census.nationalarchives.ie/pages/1901/Fermanagh/Rosslea/Cloghmore/1362737/
I looked for Henry’s death to see how old he was but I can’t find a death certificate for him.
There was also a William Watson farm in the townland too.
Henry’s marriage to Elizabeth was evidently around 1834, so well before the start of statutory marriage registration (1845). To find it you would need to rely on church records, and to do that you would need to know her denomination and where she lived. Tradition was to marry in the bride’s church. Her husband appears to have been Church of Ireland but she might have been a different denomination eg Presbyterian. And if you only know she may have come from Armagh, that’s a lot of church records to search through. Not all of which may have survived. You could go to PRONI and search through all the Church of Ireland records for Armagh. (That’s 28 parishes). The records are not all on-line so a personal visit would be required to search them all.
http://www.irishgenealogyhub.com/armagh/maps/civil-parishes-of-county-armagh.php#.Wp5doBR2ug0
Don’t expect too much information from a church marriage register in the 1830s. Often you don’t get much more than the couples names, the date and their 2 witnesses. No parents names for example.