Apple jelly question

I cooked up 1 1/2kilos of apple today to strain for jelly.After I got the juice there wasn't near as much juice as I expected.Can I add bought apple juice that has no added sugar or preservatives in it to make up a larger amount!Will it still set without adding pectin!

Does anyone have an idea about this please!

Did you put any water with the apples! Were they new season's, or last year's cold-stored apples, (which wouldn't give a great result) !
Test your juice for pectin. Take 1 tsp of the strained juice, and put in a glass. Add 3 tsps methylated spirits, and stir gently with a tablespoon. The mixture should form a clot. If the clot is a single, fairly solid, jelly-like dot, the juice is high in pectin. If several small clots form, the juice is medium in pectin content. If pectin test fails to form any clots, or there is a mass of tiny clots, then the juice is low in pectin.
High pectin juice will make a good jelly in a short time by boiling it with one cup of sugar for each cup of juice.
For Medium pectin juice, use 3/4 cup sugar for each cup of juice, and boil until the jelly sets when tested.
Low pectin juice will need about 2 tablespoons of fresh lemon juice for each kilogram of fruit used. This will bring the pectin level up a bit, so retest the pectin levels and proceed according to the results.
I've never added bought apple juice. It might work.test that for pectin as well.
I often add water to the used apple pulp and boil it up to make a second batch of jelly - it's useful when you are making blackberry and apple jelly, for instance. Apple peels and cores can also be boiled up for jelly when a quantity of apples has been used for other things. I keep a batch of the "second boilings" in the freezer (without sugar) to act as a relatively flavourless base for berry jellies. Call me tight.LOL

Thank you so much for the help.We have done the test and it had high pectin so I added bottled apple juice(it appeared to have no pectin) and tested again.It cut the pectin some so I added lemon juice.It appears to be setting but will let you know in the morning.