Astro

Overcall	Meaning
Double	For penalty. (See also: Gates Double)
2	Hearts and a minor (at least 5-4 or 4-5). 10+ points.
2	Spades and another suit (at least 5-4 or 4-5). 10+ points.
2	Natural, 5+ hearts. 10+ points.
2	Natural, 5+ spades. 10+ points.
2NT	Clubs and diamonds (at least 5-4, usually 5-5 or better). 10+ points. Partner should take his preference by replying 3 or 3.

• 2 is artificial and denies 3+ hearts. Indicates a preference for partner's minor suit. If partner has diamonds, he can simply pass. With clubs, he can correct to 3.
• 2 is a signoff.
• 2 is natural with 6+ spades. It tends to deny 3+ hearts. Non-forcing.
• 2NT is artificial, showing 12+ points and asking partner to bid his minor suit. This is the only forcing response.
• Any 3-level bid is natural and non-forcing.

		North			South
		T2			AJ9
		AQT92			K3
		AT96			J743
		T8			KJ92
West     1NT Pass		North     2 (1) 3 (3)		East     Pass	South     2NT (2)

1. Hearts and a minor.
2. Artificial and forcing, asking for the minor.
3. Natural.

• 2 is artificial and denies 3+ spades. Non-forcing, but partner may choose to bid his second suit at the 3-level.
• 2 is a signoff.
• 2NT is artificial, showing 12+ points and asking partner to bid his minor suit. This is the only forcing response.
• Any 3-level bid is natural and non-forcing.

		North			South
		AQT2			J983
		AQT92			K3
		64			J743
		T8			Q75
	West     1NT	North     2 (1)		East     Pass	South     2 (2)

1. Spades and another suit.
2. A natural signoff.

		North			South
		AQT52			43
		2			KQT83
		AJ976			J53
		T8			Q75
	West     1NT Pass Pass	North     2 (1) 2 (3)		East     Pass Pass	South     2 (2) Pass (4)

1. Spades and another suit.
2. Artificial, denying 3+ spades.
3. Natural, confirming 5+ spades. Note that the overcaller could pass 2 if his second suit was hearts.
4. Opting for the 5-2 fit rather than risk a 4-3 minor-suit fit at the 3-level. Note that if advancer held better minors (e.g. 4-4), he could bid 2NT to ask for partner's minor suit.

Astro was invented by American players Paul Allinger, Roger Stern, and Lawrence Rosler. The first letters of each player's name are concatenated to form "A-ST-RO". Since its creation, Pinpoint Astro and Brozel , two related conventions, have gained popularity. The original Astro bids are more ambiguous, and waste more space.