The timer says that you can only get an asteroid every 30 days ..
Conversely, if an attacker shot you an asteroid today, no other asteroid can emerge from you for 30 days.

In the Sirius Universe, you do not have to file an Astro Shot application.
In Sirius Universe you can own a maximum of 2 asteroids.
You can try it as often as you want ..

In other universes, you have to submit an Astro Shot application to the game operator.
After granting a license, you can try it as many times as you want and the base rules allow it ..

There is no recommended fleet size for a Astroschuss .. You have to try it yourself and try ..
You can also connect with other players who already have an asteroid.
However there is no guarantee for any statements ..
A few days ago, I shot an asteroid from an inactive player out of 53 transmitters.
But you can also lose 20,000 or 200,000 or even 2,000,000 points to fleet and get no asteroids ..
For astro shots, the random principle applies ..