Sterilize canning jars in boiling water or dishwasher. Keep hot until ready to use. Prepare new lids according to manufacturer's instructions.
Wash oranges thoroughly. Roll each orange firmly on counter to soften, then juice using citrus juicer. Strain juice through fine mesh strainer to remove seeds and large pulp pieces.
Heat fresh orange juice in large saucepan to exactly 190°F using candy thermometer. Do not boil. Maintain this temperature while filling jars.
Fill hot sterilized jars with hot orange juice using canning funnel, leaving exactly 1/4 inch headspace. Wipe jar rims clean with damp cloth.
Apply new lids and rings, tightening to fingertip tight. Do not over-tighten or retighten after processing.
Process in boiling water bath for 15 minutes, ensuring water covers jar tops by 1-2 inches. Adjust for altitude: add 5 minutes above 3,000 feet, 10 minutes above 6,000 feet.
Remove jars and cool on towel-covered surface for 12-24 hours. Check seals by pressing center of lid - properly sealed lids will not flex.
