Tutorial to become a shadow hunter

First time observing an occultation of a star by an asteroid? Read this page to master your Unistellar telescope and join our team of shadow hunters.


1. Select your mission

An asteroid occultation is a unique event to record. To catch this moment you need to be in a specific location on Earth. First, you have to select a mission near your location. Go to our Occultation Prediction Page and select an occultation you want to observe.

To find out if you will be in an asteroid’s shadow, simply zoom by scrolling on the map. If you are observing from anywhere between the two orange lines, you are qualified for the scientific mission! The closer you are to centrality, marked by the red line, the higher chance you have of detecting the occultation.

2. Read the prediction

Once you have selected a scientific mission based on your location, you need to access the observation details :

  • the time of the event
  • the coordinates of the star 
  • the recording parameters 

All of these parameters are listed on our Occultation Prediction Page. You will need these to observe the occultation.

 Based on the example above : 

  • Local date of the event : 29 July at 20h39
  • Coordinate RA:  15h 43m 01s
  • Coordinate Dec: -10° 56’ 07’’
  • Recording parameters: 300ms, 20 db and 14min00s

All these parameters are also saved in a Deep Link that you can use 10 minutes before your observation. It is the first icon of the row, illustrated by a phone.


Once your Unistellar telescope is set to observe the night sky, you can use the scientific mode of the Unistellar App. 

1. 10 minutes before your occultation 

It is time to point to your target. Two options:

    A. Deep Link method: The quickest way to find your target is to use your smartphone to click on the Deep Link associated with your event. It will automatically open the Occultation tab of your Unistellar App and fill up coordinates of the target and its recording parameters. When the Right Ascension box and Declination box are filled with the correct coordinates, click on Goto to point to your target. Once Goto is done, if the Record duration, Exposure time, and Gain are correct, click on Save.

    B. Manual method: Open your Unistellar App, click on the Science menu and select the Occultation tab. Enter the Right Ascension and Declination and click on Goto to point to your target. Once Goto is done, enter the Record duration, Exposure time, and Gain and click on Save.

2. Launch observation

At the start time, click on the Record button to start the observation.

During the observation keep an eye on your star – you may see it briefly disappear in the live view due to the passing asteroid. Once the observation is over, a final message appears: “Recording complete”


1. Share your data

Once you are at home, please upload your data to our server. Our team of scientists will analyze your observation to check if you detected the occultation. If you need help, please read these guidelines on “how to upload my data”.

2. Tell Unistellar you participated

To make sure your contribution is properly processed and you are credited for the result, always fill out this Occultation Observation Report. It asks for your name, the serial number of your telescope, and the name of the scientific mission you just accomplished. We will send you the result of your scientific mission through our Slack communication platform within 24 hours.

We will send you the result of your scientific mission through our Slack communication platform within 24 hours.

Great Work, Citizen Astronomer.