How exactly i can access my Astral body in meditation? Lord Buddha have access to unlimited knowledge, This information can be found in old Indian scriptures as well, that human body is capable to visiting to another planets with his/her Astral body (Suksham Sharir).

Is there some particular way or do i need Guru for this particular thing ?
Many Buddhist monk don't teach this, i am aware that Lord buddha himself have denied not to show any super powers.

These Siddhi's (powers) may lead to Ego, But going in universe have always been an interesting thing for anyone.
It is important to say that their is no meaning to aim for developing Siddhi. Doing so demonstrate that you are on the wrong way and therefore it will take much more time to reach them. Siddhi are fruits on the path.  

Doing things with Astral body is possible for anyone, since it is just a part of yourself. The point is to get a part big enough of your conscience to go with it.  

This as nothing to do with meditation or Buddhism. 
To have a good mediation it is more important to be here and now, well centered, and therefore with your astral body inside. Nowadays, most of the person have their astral body somewhere else (high astral, low, or around).