When you are using a telescope, it is just as important to have a stable mounting as it is to have good optics. Otherwise any vibrations will be magnified just as much as whatever you happen to be looking at.
If you are stuck with a lightweight tripod, you may be able to improve the situation dramatically by hanging a heavy weight from the mount between its legs.
You don’t even have to take the weight with you. Fill a bag with small rocks and stones or use a bottle of water to achieve the same effect.
Other observers have laid a bag of sand across the tripod’s accessory tray between the legs to get a similar result. One I know even used the sand to fill the tripod’s aluminium legs – just watch out for leaks!