The observation of stars occultations by asteroids is an exciting sport, it allows with few means to contribute to science. It is an excellent playground for amateurs because it allows with small instruments at a relatively low cost to participate in a collective pro-am work. It is photometry where the key is the measurement of the quantity of light.

Asteroids are several hundred thousand “large or small pebbles” which orbit for the most part between Mars and Jupiter. Others are more distant, those called transneptunians, a significant part has been discovered by amateurs, but nowadays it is less frequent: the most important are already listed and the big automated surveys leave less chance for discovery (like for comets)

It should also be noted that among the objects in the sky, these are the only ones to which the discoverer can give a name in addition to their official numberTheir size makes most of them very faint, they are not necessarily easy to image and it is at best only a light gray point on a dark gray background… But they sometimes happen to pass between a brighter star and the Earth, when the alignment is exactly then the star goes out for a few seconds, and then it becomes very interesting!!! It is enough to be on the trajectory of the “shadow” to make a measurement which, added to those of the other participants, makes it possible to know a lot about these objects. Unity is strength, and when many amateurs observe the same object they can then obtain quite brilliant results!

These are very precise measurements, and thinking that from your backyard (or during a trip) you can have a measurement precision of the order of a few hundred meters to 500 million km is a dream! (in a pictorial way it is the thickness of 2 sheets of newspaper seen from about fifty km!!!)

The other nice aspect is that it is a branch of astro where amateurs are very important, indeed “professional” observatories are usually not in the right area and a single measurement would not be useful. It would only confirm that its orbital elements are correct or not (if it is not observed). On the other hand, lots of amateurs spread out over the shadow path allow excellent results and draw a very precise profile. In addition to light curves, it is even possible to make it a 3D model!!

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To ensure a precise date & time, several more or less precise methods are available, but you have to reach the precision of a millisecond which is achievable nowadays with the GPS.

For years the observation was carried out with analog (video) cameras such as Watec and the dating was embedded on the image via a “box”. Corrections had to be made, which varied according to the exposure time. The maximum speed was 25 fps at best, and we often had to stack several images to get enough signal.

Nowadays, the appearance of high-performance, sensitive and fast CMOS cameras has allowed great progress. But the dating must always be included in the images.

So, some time ago I decided to “modernize” my setup: a small CMOS camera and the TimeBox: It’s definitely easier and more efficient! And in addition it is a “reasonable” budget.

I had been observing occultations for a few years, I had somewhat given up this activity in favor of others, but now it makes me want to come back! Easy to use and process data, non-captive system, it can be used with different equipments in a very easy and efficient way without having to modify a whole setup (just add the TimeBox to your PC to have a dating system). This tool can also be used for other purposes than observing occultations, in fact anything that needs a date.

A small box but a big step forward for those who want to start worry-free and without spending too much in observing occultations!