how to measure the distance to the sun

There is a way to generate the ephemeris, but it is slightly involved. The website to use is
https://ssd.jpl.nasa.gov/horizons.cgi
which is maintained by JPL.

There are a lot of options that need to be set to generate the ephemeris.

First, click on “Target Body”. Then, search for “sun” and select it. The default “Observer location” is Geocentric, but you can change that to your observation site/town/city if you desire.

Next, click on “Time Span” and choose the appropriate start date/time, end date/time and step size. The default output settings include the range and the range rate which is what you desire.

Now, click on “Generate Ephemeris”. The column “delta” shows the distance to the target (Sun in this case) in astronomical units, and the column deldot tells you the rate of change of distance.

The ephemeris is generated based on a very accurate model of the solar system and incorporates the perturbations from all the planets of the solar system. Hope this helps.

Jagadheep

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