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The Viewable Transit Service is a useful tool for planning observing runs, or if you have gaps of time in your schedule to observe some transiting exoplanets.
The service can tell you which transits are happening when their stars are visible from your current location.
Here is a sample list of all of the planets transiting during a two-day period. In the next few minutes, we'll show you how to generate your own list for observing.
To access the service, first go to the NASA Exoplanet Archive home page at exoplanetarchive.ipac.caltech.edu.
In the left panel of the home screen, click the Viewable Transit Service link.
The service interface consists of a simple form in the main panel that requires two data inputs: the observation window and the observation site.
The service requires Julian format, however, you're welcome to enter the date in the Calendar UT field and click the Convert to Julian button.
For this example, we'll set a two-day observation window starting October 25 and ending October 27.
Note that the default end date is one year later, so you'll need to change the date and the calendar year.
We click Convert to Julian, and the converted date is populated in the fields. Next, we'll select an observation site.
For this example, we'll select the Lowell Observatory in Arizona.
Note that there are several pre-programmed sites in the service. If yours is not listed, you may to enter your own coordinates in the latitude and longitude fields.
We'll click Submit, and after a few brief moments, our results appear at the bottom of the screen. These results list all viewable transits in the Exoplanet Archive
that fall within your specified period. The results contain several columns that provide information on each transit.
The midpoint is given in both Julian and Calendar formats, as well as the midpoint's altitude, azimuth and airmass.
The ingress, which is the beginning of the transit, and the egress, which is the end of the transit,
also have values for their respective altitude, azimuth and airmass.
Using these values can help you determine which transits you can you observe in a given time frame.
You may also narrow or broaden your observation window by simply modifying the start and end dates and times and re-submitting the form.
For more information about the criteria used to determine which transits are included in the archive, make sure to read the help documentation in the left
panel of the screen. For a more detailed explanation of how calculations are performed for each epoch of periastron and observed transit midpoint,
click the User Guide link at the bottom of the left panel.
To provide feedback on the service, click the Helpdesk link in the upper-right corner of the home page,
and submit your feedback through the online form.
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