How to find the angle in circle movement?

Iam making a planet revolving type game, in which the planet is revolving around the orbit, and when we press the key the planet would release from that orbit and move towards the second orbit and then start revolving according to that. The problem is that, the angle at which i release the planet and the angle at which the planet would collide with the second orbit is definitely not same. Is there any mean to find the angle through position? or any other formula.

You can use the angle expression.

angle(sun.X, sun.Y, planet.X, planet.Y)

at the time of release or at the time of collision with other orbit?

Every tick during the time between release and collision, so the trajectory is smooth and adapted to the current positions during their evolution.

Sorry for being so late for replying back and say thanks.....Thanks alot for the help... Just need one more help.... I want to make infinite game, in which rocket is revolving around the planet, when key is pressed it leaves that planet and move to the next planet in y axis and so on. what iam doing right now is moving planets downward to make it infinite. is there any way that if i dont move the planets and just rocket moves inifinitely.? or anyone just give me the idea that how can i make it infinite

Are you talking about an infinite vertical scrolling (whereas your main objects are "staying in position") ?

Check out the "Scrolling / Camera" section in the How do I FAQ for Construct 2 to get ideas on how to implement it.

Or check this page of the tutorial that talks about horizontal scrolling, and adapt it to your needs.