Several suggested procedures and strategies are available for planning coronagraphic observations with JWST.
Parent article: JWST High-Contrast Imaging
Coronagraphic and other high-contrast imaging (HCI) observations can be some of the most complex to schedule with JWST. Most HCI science requires the scheduling of a sequence of observations that collects data for the primary science target as well as a reference star to support point spread function (PSF) subtraction.
The JWST PSF is expected to be time variable, which has important consequences. For example, both the science target and PSF reference star will be reduced together; therefore, they should be observed as closely together in time as feasible in order to minimize changes in the PSF. This brings into play the issue of target visibilities, which is discussed later in this article. Unless on-orbit experience shows that this need for contemporaneous imaging can be relaxed, the JWST project requires observations of the HCI science target and PSF reference star to be planned and coordinated to execute together, in a back-to-back sequence of observations.
Ultimately, the limiting contrast is controlled by PSF variability.
Depending on the specific goals of your HCI science program, a number of planning options and issues may or may not apply to your particular program. For example, do your goals call for the default 10° roll dither on your science target? Is a larger position angle offset needed to recover a part of the scene that would otherwise be blocked by the selected coronagraphic mask (e.g., a face-on disk observed with a NIRCam bar occulter)? Is the highest quality PSF matching needed for your science? If so, perhaps you should consider the small grid dither (SGD) technique. In the case of NIRCam observations, do you need high accuracy astrometry? If so, perhaps you should obtain images for full field astrometry (FFA) in addition to the HCI science data (article pending).
Your most basic decision in planning HCI observations is your choice of wavelengths needed for the science. The choice of wavelength ranges will influence your choice of science instruments and the options for masks, filters, and detector operations. See the JWST High Contrast Imaging article for links to the details on individual instruments.
Estimating your exposure times is a science-critical aspect of observation planning. You must estimate exposure times for both science observations and target acquisition, which is crucially important for the success of coronagraphic observations. You can estimate exposure times using the JWST Exposure Time Calculator. Some HCI-specific suggestions on using the ETC are available in JWST Coronagraphy in ETC.
Below, this article treats planning topics in more detail, providing links to other articles for additional information.
Outlined below is a suggested flow of planning considerations to help you through the process. We recommend checking target visibilities first (since running ETC calculations for a target that is not observable at the necessary position angle on the sky is a wasted effort). Also, some users may want to consider the strategy issues up front in their planning.