Wash well and cut 3 medium sized oranges into thin segments
The rest which from memory were probably close to 15 peel and place into a juicer to do all the hard work, ideally where the pulp can be separated
I added the juice and the skin segments to a pan and warmed through then added sugar, once I could see it turning glassy I added a few tablespoons of pulp
This make it full of body and stops it being too sweet and lots of fibre..
Quantities will vary but I find its close to equal parts sugar to liquid
To see if you sugar syrup is close get a cool plate and drissle some on and if it goes rock hard you have toffee so not what you are looking for.
I would normally start testing one sugar dissolved and comes to boil and every 5 to 10 mins intervals til I achieve what I want.
Ideally we want it to run but cease which means it will be more of a soft set.
I tend to do this by adding sugar in gradually , so not all at once, I also used raw sugar which also give a more complex caramel flavour to the jam.
This turned out very scrummy and even my father in law requested more...