Astro

Named for its American creators Allinger, Stern and Rosler, Astro is a defensive convention for use against an opponent's 1NT opening. 

Over an enemy 1NT,

• 2: Hearts and a minor, 12+ points
• 2: Spades and another suit, 12+ points
• Double and all other overcalls are natural.

Advancer's rebids to 2 are:

• Pass: Long club suit, signoff
• 2: An artificial relay denying 3 cards in the anchor suit (hearts)
• 2: Signoff
• 2: Long spade suit, signoff
• 2NT: 10+ points, one-round force, asking overcaller to bid his second suit
• 3: Invitational

Advancer's rebids to 2 are:

• Pass: Long diamond suit, signoff
• 2: An artificial relay denying 3 cards in the anchor suit (spades)
• 2: Signoff
• 2NT: 10+ points, signoff, asking overcaller to bid his second suit
• 3: Long club suit, signoff
• 3: Invitational

If advancer gives the relay response (2 to 2 and 2 to 2), overcaller's rebids are:

Pass: The relay response happened to be overcaller's second suit

Two of the anchor suit: A good five-card suit or better. Opener should bid his good anchor suit first before showing a good second suit.

Cheapest second suit: A good five-card suit or better If overcaller rebids two of the anchor suit, advancer may rebid 2NT to ask for his second suit.

Pinpoint Astro

uses the following overcalls of 1NT:

• 2: Clubs and hearts
• 2: Diamonds and hearts
• 2: Hearts and spades
• 2: Spades and a minor