A New Experiment for Zero Shadow Day

A Zero Shadow Day is day when the Sun will be directly overhead at local noon. It can happen only in locations between the Tropic of Cancer and the Tropic of Capricorn. The Sun never reaches this point on any day in locations north of the Tropic of Cancer and south of the Tropic of Capricorn. Between the Tropics, this happens twice a year. You can read more about Zero Shadow Day here.

Usually, we will carry out experiments where we place objects like cylinders and blocks and observe that there is no shadow at local noon.

Glue Bottle with no shadow at local noon on Zero Shadow Day
Glue Bottle with no shadow at local noon on Zero Shadow Day in Bengaluru, India (24-April-2021 12:17pm)

For a change I decided to use a different cylindrical shape – my Newtonian Telescope – and instead of looking at the shadow, we will look straight up at zenith – WITH A SOLAR FILTER COVERING THE ENTIRE APERTURE AND ALL USUAL SOLAR PRECAUTIONS. So I covered the aperture with a solar filter, connected the camera and left my Newtonian telescope aperture up – checked the level to ensure it was more or less pointing straight up. (using my mobile leveling tool)

Newtonian pointing to Zenith on Zero Shadow Day
Newtonian Telescope with Aperture Solar Filter and Mirrorless camera attached, placed level on the ground pointing to Zenith on Zero Shadow Day

If the Newtonian telescope is properly level, then the Sun will drift into view of the camera when the Sun is about to reach zenith. Check out the image below which was taken by the setup above when the sun reached zenith.

The Sun at zenith on Zero Shadow Day, 24-April-2021 at Bengaluru, India captured with a Newtonian Telescope using NO MOUNT. (FOLLOWING ALL SOLAR PRECAUTIONS, FULL APERTURE SOLAR FILTER USED)

You can catch the video below.

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