Page 20 - Astronomy Book 1

Mars is said to be at Opposition
(closesest to) Earth every 26 months.
This is because the Earth takes a year to

orbit the sun, and Mars takes about two
years.
Therefore every 26 months, we gain a
lap on Mars, passing between it and the
Sun.

Not all Mars' oppositions are equal, and
one shown here (October 13th 2020)
was a very close one. Extra-close
oppositions of Mars (less than 37 million
miles) recur in periods of 15 to 17 years
and the next one will not occur until
September 15, 2035.

By using the video camera hundreds of
frames can be captured using exposures
as short as 1/120sec. Due to changes in
atmospheric turbulence some of these
frames show more detail than others.
These frames can be automatically

selected using software such as
Registax and finally combined to give
much improved images of the planets.

By combining the individual views in specialist software you can create a map of the surface in
20 equirectangular projection