Find Exoplanet Transits

This form calculates which transits of the 3302 known transiting exoplanets or 4471 TESS Objects of Interest (TOIs) are observable from a given location at a given time. Specify a time window, an observing location (either an observatory from the list or choose "Enter latitude/longitude" at the end of the list), and optionally any filters (e.g. minimum transit depth or elevation). The output includes transit time and elevation, and links to further information about each object, including finding charts and airmass plots. (There are also stand-alone pages for generating finding charts (annotated JPGs or using Aladin Lite) and airmass plots for any target.)

Latest update (Sep. 2021): The database of transiting planets used below is currently slightly behind the NASA list and does not include transiting planets added to the NASA Exoplanet Archive since April 2021. I need to find time to update the code to deal with their new table format. I hope to do that soon. (The TOI list is up-to-date.)

Target list:

NASA Exoplanet Archive database (3302 planets; CSV file)
TESS Objects of Interest (4471 TOIs; CSV file; Apply to join the TESS Follow-up Program)
Single object with given ephemeris (date and elevation filters below still apply).

Note: to search for a specific known transiting exoplanet, don't use this. Choose "NASA Exoplanet Archive database" above, then enter the target name below in the box labeled "Only show targets with names matching this string." Use this only if you want to manually enter the ephemeris for some other target (or try an alternate ephemeris for a known target).

RA (J2000):  
Dec (J2000):  
BJD of mid-transit:  
Period (days):  
Transit duration (hours):  
Transit depth (ppt):  
Target name (optional, for labeling only):  


Choose an observatory, or choose "manual coordinate entry" at end of list:

Use UTC  /  Use observatory's local time.

Date window:

Base date for transit list (mm-dd-yyyy or 'today'):

From that date, show transits for the next days.
(Also include transits from the previous days.)



Only show transits with an elevation (in degrees) of at least:

at ingress:     Combine constraints with AND OR.
at egress:

Unspecified elevation constraints default to 0. Constraints are evaluated at night, i.e. to be shown as observable an event has to meet that elevation constraint during nighttime hours.

Hour angle:

Only show transits with hour angle between and hours. Constraints are evaluated only at ingress and egress. Unspecified HA constraints default to ±12 (i.e. no constraint).

Out-of-transit baseline:

Also calculate observability (with above elevation, daylight, and HA constraints) at points up to hours before ingress and after egress to show how much out-of-transit baseline can be observed.

Extend baseline by ephemeris uncertainty. (If baseline above is zero, this option will display baseline of uncertainty only.)

Space observing:

Ignore all elevation, hour angle, and day/night constraints; show all transits. Useful for space-based observing (but can generate lots of output if no target constraints specified).


Only show transits with a depth of at least parts per thousand (ppt).

V magnitude:

Only show targets brighter than V = .


Only show targets with names matching this string: .
(Not case sensitive; can be a Perl regular expression.)

Output format and labeling:

Output results as:
HTML table
CSV file for parsing by script.
CSV file for calendar import. (Save resulting output to a text file, then import into your observing calendar, e.g., import into Google Calendar.)

Day/night definition: start night at Sun altitude of  
The above choice determines both which events are displayed (since part of the transit must be at night), and which parts of an event are color-coded to indicate daytime.

Maximum airmass to show in airmass plots:  
(Current airmass value of 2.4 is elevation of 24.6 degrees.)

If this tool is useful for your research, please consider citing it, e.g. Jensen E. L. N. 2013. Tapir: A Web Interface for Transit/Eclipse Observability, Astrophysics Source Code Library ascl:1306.007.

This page uses input ephemeris data from the NASA Exoplanet Archive and ExoFOP-TESS. The finding charts provided here make use of images from the Digitized Sky Survey, which are subject to copyright, and can be acknowledged like this.

This tool is part of the Tapir package for planning astronomical observations; the source code is freely available.

This page was created by Eric Jensen. Feedback welcome! Send here.