# Phase Constraint Calculator

The Phase Constraint Calculator provides a simple interface for calculating the JWST observation start window. The calculation currently only applies to transits, though one can subtract 0.5 from the phase values to compute the eclipse observation start window for planets on circular orbits. Enter the minimum and maximum phase values into the APT special requirements section when planning your observations.

The name of a target to resolve in ExoMAST

$$\small \text{Days}$$
Period of Target

$$\small \text{BJD or HJD}$$
Transit time of Target

$$\small \text{Hours}$$
Length of Your Observation (Default 3*(transit duration)+1 [Hours] when using Resolver)
$$\small \text{Hours}$$
Size of observation start window (Default 1 hour)

Calculate Phase Constraints for Target.

Minimum Phase of Observation

Maximum Phase of Observation