I already made a two entries about observing and measuring double stars (here and here). Over last one year and half I had a few sessions with this interesting type of objects. Many of them are only visual doubles: stars are apparently close to each other, but in the space they are not interacting in any way. But some of them do interact and orbit around common centre of mass. Much patience is required to do measurements that spans over years or sometimes even decades, so the actual orbit can be determined.
There is convenient search engine for Washington Double Star Catalog (WDS) – Stelle Doppie website http://stelledoppie.goaction.it/ . Here you can find some candidates for further measurements: stars with low number of observations and/or where last observation has been made long time ago. During my double star sessions I have made over 40 measurements that are listed in the table below:
All these data was collected at my backyard roll-off observatory with Meade ACF 10″ telescope on EQ6 mount and QHY163M camera with Baader V filter. First columns contains data from Stelle Doppie site about position angle and separation of the system. Then we have number of observations in WDS database, and measurement done by me: date, position angle, separation, magnitude difference, subframes used for measurement and sigma value for both PA and separation. All data was processed with REDUC software. Each star observation contains 10-30 subframes, each subframe exposure time was in the range from 2 to 6 seconds.
Good news is that high accuracy can be achieved even with amateur setup when measuring double stars. Good seeing is important factor for double star observations. System does not need to be separated completely to do measurement using REDUC software. But good seeing gives better accuracy for both position angle and separation values.
Below there is collection of double stars images that was made during observations. Each image is stack of (usually) 80% of best subframes. It was then rotated to the same orientation, and annotated with system and component name, directions and scale. Image scale is the same for all: 0.22″ / px .
Clear skies!
