Wash blueberries, sort and drain well. Wash the orange under hot water, dry it and peel the peel thinly. Cut the peel into very fine strips.
Squeeze the orange. Crush blueberries until mushy, mix well with orange peel strips, orange juice, crushed juniper berries and Viennese jelling sugar in saucepan, bring slowly to boil and simmer for 6¿8 min. while stirring. Make a jelly test. Pour hot to rim into prepared jars and seal immediately. After a few minutes, turn upside down and let cool.