This week we have a look at the history of data taken for HOYS by our participants (sorry, no actual light curve). In the plot we show (as a blue line) the number of images that were observed before a given date and then submitted into our database. As one can see, we now have a total of about 67500 images for analysis.
The plot also indicates some of the milestones of our project, such as the inception in the autumn of 2014. Just under one year later, we opened our new university observatory, which has been used to support the project throughout. In total about 17 percent of all images are from this observatory. In the early autumn of 2017 we opened our database in its current format. There are also red shaded areas for our major observing campaigns that were run with the help of AAVSO and in support for the HST legacy program ULLYSES.
In the top we indicate with green ticks the dates when we published papers with data from the HOYS project. As you can see, we are currently averaging about two papers per year. The next two are now in the final stages of writing and should soon be finalised. In the bottom, the blue tick marks indicate the dates were we have given talks about the project to Amateur Astronomical Societies or at Amateur Conferences. Supported by funding from the university, we made a concerted effort in 2018/19 to reach out to about 40 UK based societies. In the following years, we have continued these presentations at a lower level. This was mostly caused by the pandemic and of course by the fact that we are slowly running out of UK societies we did not yet visit. But we are still offering presentations in person or online if requested. Our first talk to a US based (New Mexico) society has been scheduled for later this year.
There are a few interesting details visible in the number of images over time. We first note that we have now collected just over 1000 images that were taken before the project had even started. These are vital for our investigations of the long term behaviour of the young stars. We can also see that the slope of the blue line on average keeps getting steeper. This means that we have more and more images taken for us per day. This reflects the ever increasing number of people observing and submitting their images. The average rate since the first image is 21 images per day, and is indicated by the diagonal dashed line. But you can see that during the last two years the typical image observation rate is about 50 images per day.
One final detail worth noting is the ‘leveling-off’ of the rate during spring time each year. This is very evident this year and also in 2020. The reason for this is the setting of all winter targets at sunset, while the summer targets only rise later during the night. Thus, most southern observers have no targets or only targets early morning. This phase is now over, with the summer targets in Cygnus and Cepheus visible all night. However, of course the shorter nights in the summer still continue. But we can already see a small uptick in the rates in the top right of the plot. There is not much we can do to improve this situation. Almost all young clusters and star forming regions are situated in or near the Galactic Plane. And during the Spring months, the Galactic Plane is basically situated all around the horizon for many hours of the night. Thus, there are no targets available.