Hello Is there any standard for how long it terms of number of scenes/chapters for the main character may be invisible ?
Certainly not the kind of thing one can answer numerically, but I would hazard that if your question is less hypothetical and more about you looking at your WIP and worrying you may have passed some impossible-to-pin-down number, then your gut feeling is probably right. Again, assuming the hypothetical is less hypothetical and more concrete.
its also possible that the person you identify as the main chaacter isnt actually the main character at all, and you'd be better off leaving them off screen entirely and identifying a different protagonist
Why are you leaving the main character offstage for so long? If you can pin down that answer, you'll probably have better insight into the situation. And is the 'main character' really the main character, as @big soft moose suggested? Obviously they're not the overall POV character, or we'd have them from the opening scene. You could certainly play around with having more than one POV character. You could also create a prologue, if you're simply setting up a scenario for the main character to step into. The good thing about a prologue, is it sends the signal to the reader that this bit, while vitally important to understanding the story, does NOT necessarily contain your main character. Therefore when the story's focus switches TO the main character, the reader is prepared for the switch. Just keep writing, though. The answers to these dilemmas will come clear, the more you write. You may discover that all the preliminary stuff isn't even necessary at all. What if you just started with your 'invisible' main character? How could you work this?
Depends on which perspective mode you're using. First Person: None. If your main character isn't in the scene, then you are doing it wrong. Third Person Limited: None, technically. However, it's easier to cheat with this one. Third Person Omniscient: However long you deem appropriate, I guess? That Weird Hybrid Thing Jonathan Stroud Did Which Managed To Be Both First Person And Third Person At The Same Time: I guess theoretically you could treat this as Omniscient for most of the story if you feel like it and keep the First Person part as a surprising twist, but otherwise I wouldn't go beyond 50%.
My thoughts There are stories without the main character. Which tells stories and events from the outside. Such stories are not frequent, but if the events are very interesting then such stories work.