Unless your enemy is called Custer and the AI is not as stupid as him they will not split up , they will go to your biggest planet and blow it up, then go to each of your decoys and blow them up defeating you in detail.
If you concentrate all your defenses they can still blow up your mining sites but hopefuly not your homeworld and hopefully the homeworld defenses will hold until you get your fleet back from where ever you sent it while your home system is under attack. Or your fleet is dead in which case you have a problem.
In the meantime the huge amount of resources you seem to want to divert to create decoys could have been spent on building a fleet and winning, and unless each of your decoy's has the same population and industry as your homeworld (which will cost more than the same on your homeworld) then they are not as attrative targets IF they are as big a target as your homeworld they are not decoy's they are critical facilities which need the same level of defenses as your homeworld,

A faster fleet can pick the range, but splitting up splits your anti-missile defenses and each of your small mobile fleets dies from missile fire when a single fleet would have emerged victorious , or you had much more fleet than you needed and each of your dispersed fleets is stronger then the enemy

Have a look at the system map, look at the range circles around your fleet, notice that at any reasonable scale the range circles of your beam weapons are the same as the dot of the ship. Beam weapons on an asteroid will not bother an enemy fleet unless it closes to beam range to attack the asteroid , in all probabilty they will not even see small mining colonies and if they do and decide to attack the massed fleet will kill your small number of STO without noticing them except for dinged shields and armour. 3*10^5 is a good beam range, an AU is 1.5*19^8km about 500 times larger the Earth is 1 AU fromt the sun WP are typically further away, the chance that a random straight line between the WP and the destination of a fleet will come in range of an STO is less than winning the national lottery

Buying time for your homeworld is a nice idea but when the enemy is in your home system it is too late the time taken to build warships and STO weapons is measured on a much longer time scale than the time taken to nuke a planet. Buy time by killing all the survey ships before they find the WP to your homeworld or by already having built a fleet . Having said that in a previous Aurora version there is a game report of someone rebuilding while his home system was under attack by an NPR and winning but all his defenses were on his homeworld not spread out pointlessly and that is only possible because the NPR AI is not as good as a player.

Several hundred STO can hurt a fleet badly as long as it does not have a range advantage , 10 or 20 may hurt one ship before they are destroyed , 1 or 2 will barely be noticed.

I think your theories need some experience of the game. If they work tell me about it I will be suprised and impressed

Making the enemy surrounded on all sides with numerous smaller fleets and sources of attack.

Well, with options of asteroid and planet motion in mind, if there is an asteroid between a jump point and a colony, I'd certainly like to put a small amount of STOs to make it show it's military capabilities/reduce it's missile reserves/buy time.

Coming back to other strategies and tactics - I've noticed that you can order your ships to activate transponders - could this theoretically help in luring an NPR/spoiler into an ambush or distract the enemy force, by presenting a target of low importance?

Unless your STO weapon is on the colony under attack it is probably useless. Beam weapon ranges are less than a million km, usually much less. Most ateroids are more than a million km from each other. Anti-missile STO which are rather vital to prevent your colonies being nuked have to go on the target as they have even shorter engagment ranges
Put the Beam weapons on the target you want to defend.  Small numbers of STO's are easy to kill so won't do much at all against any force worth worrying about so if defending Sol put them were you have populations or vital mining colonies, same in other systems. In a multiplayer controlled set up you may for RP reasons have very small groups of ships in which case small STO batteries may achieve something , they will not against NPR's.

When an NPR attacks a solar system they will usually go for the highest signature target (Earth) as they may well not even detect small mining colonies. Same goes for you when you attack. Due to my particuarly poor scouting I had my main fleet in a system and failed to notice a moderate size mining colony with a fleet in orbit over it until the fleet moved out and attacked me.

Yes, this was a common tactic if Mars needed defending.  Eventually you could do the same with Luna and Earth if you didn't create atmosphere on the moon.

As to your original plan, putting small STO units here and there in the Sol system only works if you're playing a multi-faction Earth/Sol start, where you roleplay several powers.  Because then you can have a fuel depot on Ceres, guarded by STO unit, for example.  Or you could sneakily put STO units on a comet while it's away from the inner system and then have them open fire at your enemy when the comet returns.

But none of that is useful in any way against NPR or spoilers who will just beeline towards your colonies.

Problem with STOs on asteroid is limited range of beam weapons. Something like batteries on Phobos and Deimos makes sense as they will be able to protect Mars and it can also limit environmental damage as enemy will not have to attack Mars to destroy the STOs, but STO batteries on Eros would most likely have no effect on defence of Sol.

Quote from: Black link=topic=12567. msg152573#msg152573 date=1623231197

Problem with STOs on asteroid is limited range of beam weapons.  Something like batteries on Phobos and Deimos makes sense as they will be able to protect Mars and it can also limit environmental damage as enemy will not have to attack Mars to destroy the STOs, but STO batteries on Eros would most likely have no effect on defence of Sol.

I suppose the range limitation can be, to an extent, circumvented with high-end technology?