Before starting a big series of double stars measurement I wanted to make sure that the current configuration which I start using in the last months is capable of producing scientific valuable data in close double star measurements. The older projects I had on double stars astrometry used different equipment and also different data reduction procedures and software. Now I capture wide field pictures using CPC8 Telescope and Canon camera and extract precise components coordinates for each component, using the rest of the stars from the field to determine the exact position of the picture ( using Astrometrica software ). Even if at some basic computations based on the equipment characteristics suggested me that I shall be able to get good enough accuracy for double stars down to a few arcseconds I wanted to confirm this by test measurements and started a long period of tests. This period was much longer than I expected mainly because of bad weather but also because of some mistakes I made ( which was very useful to help me learn a lot of interesting things ). I will not describe here more technical details about the techniques , equipment, problems and solutions because is not the right place here for this. These will go to a dedicated article about this project. Please feel free to contact me if you want to know such details before the article will be available ( which might take some time )
So.. finally I managed to confirm a decent accuracy for double stars down to 5 arcseconds in separation by succesfully measure some low speed double stars which has recent evaluations. The results are most clearly visible in the next graphs.
Shortly the average errors are 0.79 degrees on PA and 0.19 arcseconds on separation. Maximal errors obtained on the test sample is 1.28 degrees on PA and 0.41 arcseconds on separation. This means I can safely measure with good accuracy double stars down to 5 arcseconds separation. The limit might be pushed a little more but for the moment I stopped with the tests at the 5 arcseconds level and I intend to start a series of effective neglected double stars measures which are in this range.