These are examples of cosmic ray hits on the CCD/detector. Cosmic rays are typically charged particles or very energetic gamma rays. When they impact the detector the generate electrons (like the light from the stars) which are then detected. If the detector gets hit by protons or alpha particles (Helium nuclei) they usually result in brighter, straight streaks. Gamma rays tend to create more point like ‘cosmics’ which do look like stars sometimes – you can also get them when a proton impacts the CCD at 90deg. Again, we take the three images to median combine them and remove these features.
For these, you can use SIMBAD to find potentially interesting young stars in the clusters and the look up their light curve in our database. There is no need to point the telescope at the star you are interested in during the observations. Indeed, it is not very helpful. The target coordinates on our list are chosen to maximise the number of young stars in each image. Hence, if you point not at the central coordinates, you potentially image a lot of area that does not contain any young stars.
Any straight (sometimes slightly wiggly) lines are typically satellites. They can be much brighter and if you look through other data on LCO you will find many more. Since we take three images and then determine the median of them in the stacking, the streaks usually disappear in the stacked images.
You should pick one of the HOYS target regions from the list on the website and use these coordinates for the pointing of the telescope. And you should take 3 images with 120s exposure in each of the filters (V, R, I). These are completely sufficient for the photometry of the stars in these clusters.
