Tutorial on Visualizing Dithers of a Solar System Observation in APT

An example for how to view dithers for a solar system observation in the JWST Astronomer's Proposal Tool (APT)

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Main article: JWST Astronomers Proposal Tool Overview

Currently APT does not have the capability to display an Aladin visualization of moving target dithers. This update is expected to occur around Cycle 2. In the meantime, moving target observers can use a fixed target as a proxy to visualize their dithers. Accurate instrument field of view orientations can be determined using the Moving Target Visibility Tool (MTVT).

To learn how to download APT and start a JWST proposal, see Moving Target APT Instructions. Before this tutorial you may want to read Tutorial on Creating Solar System Targets in APT and Tutorial on Creating Solar System Observations in APT. If you have questions please contact the help desk.

Viewing dithers with a proxy moving target

In the example below, we define as a proxy for Callisto a fixed target, M-35 (an open cluster on the ecliptic). Visualization of the instrument FOV, placement of the FOV for various dither and mosaic-tile offsets, and depth of coverage is then possible by changing (temporarily) the target of the observation from Callisto to M-35. In order to visualize the dithers, click on the View in Aladin button at the top of the window. The Aladin viewer is discussed here.

Figure 1. Defining a fixed target proxy.

In the Aladin window any observations you have highlighted in the page tree on the left will be displayed over the sky catalog of your choice (DSS, 2MASS, Simbad, etc.). 

Figure 2. Viewing the observation in Aladin.

Pan and zoom to display at the level you want. This screenshot shows a NIRCam sub-pixel dither. 
Figure 3.Visualizing a sub-pixel dither.


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