Guidelines for AO Users

Selecting Observing Conditions – Guidelines for AO Users

For Seeing use the following table:

Vmag			Desired Strehl Ratio
	> 0.8	> 0.6	> 0.4	> 0.2	< 0.2
8-10	Good < 1.0	Poor < 1.2	Poor < 1.2	Poor < 1.2	Poor < 1.2
10-12	Best < 0.8	Poor < 1.2	Poor < 1.2	Poor < 1.2	Poor < 1.2
12-14	Not possible	Good < 1.0	Poor < 1.2	Poor < 1.2	Poor < 1.2
14-16	Not possible	Not possible	Best < 0.8	Good < 1.0	Poor < 1.2
16-18	Not possible	Not possible	Not possible	Best < 0.8	Poor < 1.2

For Background always use grey.

For Cloud Cover specify clear (or specify thin cirrus, but in this case add 2 to the Vmag of the reference before selecting Seeing from the above table).

The information given in the above table was derived from the following sources:

• Commissioning Report
• A preliminary document used for discussion on 01Aug2024
• Staff experience

The suggested values in the table above are for H-band, on-axis. For shorter wavelengths, and/or an off-axis reference, make more conservative selections (i.e., better conditions) for Cloud Cover and Seeing. Consult your support astronomer for assistance.

Note that under any of the following circumstances:

• Seeing above 1.5″, stable or variable.
• Seeing above 1.2″, variable.
• Variable extinction

LBTO will declare that conditions are not suitable for AO, even for programs that have low AO performance requirements. In these cases, if the PI and/or mini-queue coordinator wish to proceed with AO despite the LBTO declaration, the observation will be considered shared risk. Further, any AO performance statistics gathered during that time will not be included in the official reports produced by the AO group.

These recommendations are for diffraction limited AO. Similar information for ESM is TBD.