[Rooks]

if I am attacking a spirit while astral perceiving is it astral combat+willpower or agi+weapon skill + weapon focus?

[Sphinx]

SR5 p.315: "Astrally perceiving and dual-natured characters use their physical attributes and skills to fight opponents with a physical body, and their Astral Combat + Willpower to fight wholly astral entities."

[Reaver]

Has the spirit materialized?

If yes, physical combat.

If no, astral combat.

[Rooks]

and damage code is str if materialized and cha if not?

[Sphinx]

Yes, adjusted for the Weapon Focus if you're using one.

[Reaver]

Yea, the key is the state of the target...

If the target is on the astral, then its generally astral combat. If the target is on the physical, then its regular combat.

[Jack_Spade]

I'm pretty sure dual natured critters can use unarmed combat with their critter attacks to combat purely astral opponents.

They'd be sitting ducks for any astral intruder otherwise.

So imho if the astral entity stays within reach you can in fact use normal combat with a magic weapon to hurt astral beings. Astral combat is most useful if you aren't within your own body.

[RowanTheFox]

I'm pretty sure dual natured critters can use unarmed combat with their critter attacks to combat purely astral opponents.

They'd be sitting ducks for any astral intruder otherwise.

So imho if the astral entity stays within reach you can in fact use normal combat with a magic weapon to hurt astral beings. Astral combat is most useful if you aren't within your own body.

Nothing pisses off a harrow faster than a dual natured headbutt.

[The Bald Man]

So two materialized spirits can not Astral Combat at each other?  straight up physical combat is going to take forever if their attacks don't ignore the immunity to normal weapons. 

[Jack_Spade]

But the attacks of dual natured entities are by definition magic so immunity does not apply.

[Finstersang]

It depends if either your or your opponend are only Astrally Percieving/Dual Natured or fully in astral space. 

If your target is in astral space only (i.e. if the spirit hasn´t materialized), you can attack it only with the astral combat skill (or mana spells). You have to be either Astrally Projecting or Astrally Percieving to do so. If you have a weapon focus (or rather: the astral equivalent of your weapon focus) with you, you can use it to attack for higher damage and sweet bonus dice. However: You still use astral combat and your astral attributes, even when attacking with an astral sword. (Note that if you are only Astrally Percieving, it might be difficult to effectively combat fully astral threats, as their high astral movement rate would allow for quick retreat and/or nasty hit&run-tactics. Ask your GM if (s)he allows for Astral Grappling and/or Astral Interception! Both are not explicitly mentioned in the rules, but one can argue that Astral Combat is analogous to Unarmed Combat in this regard.)

If your target is Dual Natured (i.e. a materialized Spirit) and you are astrally Projecting, you can also only use astral combat, since you have no body to dish out the blows.

If you and your target are both dual natured and in close combat, you can choose to attack either using Astral Combat or the fitting physical combat skill (Unarmed Combat, Blades etc.)

And last but not least: If either you or your target are not active in astral space (i.e.: at least astrally percieving), you can´t use astral combat at all.

[Jack_Spade]

Time to get some rules into this discussion:
p.312
"When astrally perceiving, you become dual-natured (meaning you have presence in both the physical and astral planes simultaneously) and can interact with astral objects, including through combat."

p.315
"Astrally perceiving and dual-natured characters use their physical attributes and skills to fight opponents with a physical body, and their Astral Combat + Willpower to fight wholly astral entities. Astrally projecting characters use their mental attributes in place of physical ones (see Astral Attributes Table) along with the Astral Combat skill. There are no ranged weapons that function in astral space, so unarmed attacks, active weapon foci, and mana spells are the only options for astral combat."

p.394
"Whenever a critter flies, rends something with its claws, or paralyzes a target with a mere touch, it’s using a critter power. Powers are the special abilities that a critter possesses. Some critter powers are natural, such as their claws or tough skin.[...]
In order for a critter to use a power against a target, they have to be in the same state, either astral or physical. Astral forms cannot affect physical targets, and physical forms cannot affect astral targets (see The Astral World, p. 312). An astral critter that can materialize can affect physical targets if they do so, however, and dual-natured critters can interact with the astral plane as easily as the physical one."

"A dual-natured critter with a melee Natural Weapon can use this power against astral targets that are within its reach. Use the critter’s normal Unarmed Combat skill and physical Damage Value for this attack. Ranged Natural Weapons, like other ranged combat, do not work on the astral plane. Critters without a Natural Weapon may still make an unarmed attack. As with regular characters, the Damage Value is (STR)S. "

Ergo: It is possible to attack purely astral beings with your claws and fists as long as you are dual-natured.