Planning Moon observations with my QO-100 station

There is a saying that goes like “even a broken clock is right twice a day”. In the same spirit, even a QO-100 station, which is installed with a fixed dish aiming to Es’hail 2, can sometimes be used for observing the Moon, as it happens to pass in front of the beam.

My station has a 1.2m offset dish with a GPSDO disciplined LNB. There are a few things that can be done when the Moon passes in front of the beam of the dish, such as measuring moon noise (though the increase in noise is only of around 10K with such a small dish), or receiving the 10GHz EME beacon or other EME stations. Therefore, it is interesting to know when these events happen, in order to prepare the observations.

I have made a simple Jupyter notebook that uses Astropy to compute the moments when the moon will pass through the beam of the dish (say, closer than 1º to the position of Es’hail 2 in the sky). Of course, the results are highly dependent on the location of the groundstation, so these are only valid for my groundstation and perhaps other groundstations in Madrid. Other people can run this notebook again using their data.

It turns out that each year the Moon passes roughly a dozen times in front of the dish beam. The next observation for me is on May 16. The separation in degrees between the centre of the Moon and the centre of the dish beam can be seen in the figure below.

This notebook can be used to plan for transits of other astronomical objects, but besides the Moon and the Sun, there are no other objects that are visible at 10GHz with a small dish. It is well known when the Sun passes in front of the beam, since this disturbs communications with GEO satellites. This is called Sun outage and it happens during a few days around the equinoxes (a few weeks sooner or later, depending on the latitude of the station). On the other hand, the transits of the Moon happen throughout the whole year, at rather unpredictable moments, so I think this notebook is quite useful to plan observations.

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