Like for many amateurs the winter weather in my location on the Oregon coast has been very poor recently. At such times with cloudy nights I enjoy researching resources on the internet or in SkySafari. It is also interesting to examine records of past observations of different celestial targets as recorded in my astronomical observations spreadsheet.
This Excel spreadsheet is set up so that the entire 3600+ list of observations can be sorted by any column heading, the most useful being Date or Object. Sorting by the Object column displays all observations of a particular object for all dates. To facilitate examining the 1100+ double star observations I edited each double star observation note to begin with the words "Double star". So when the list was sorted by Observation, all the double stars were grouped together. Then all the double star observations with separations of less than two arc-seconds separation were color coded with the Object cell filled with red. When I then sorted all objects by color, the closest doubles were at the top of the list shown in red. These observations were copied over to a separate Close Doubles sheet, part of the overall spreadsheet. Other sheets in the spreadsheet are: Observations, Instruments, Abbreviations, Sites & Observatories and Drawings.
I was interested in examining observations of doubles stars that would be up against the theoretical resolution limit, either the Dawes- or Raleigh-limit for the aperture being used. One problem encountered was correcting the recorded component magnitudes and separations. Often what had been originally recorded in the spreadsheet was from a Sky and Telescope article, Norton's Star Atlas, Burnham’s Celestial Handbook or other old published reference. For the closest doubles the components are often binaries with appreciable change in separation depending on the date of the observation. So for all close doubles I corrected the recorded brightness and separations using Stelle Doppie for the date of observation. In almost all cases this wasn't too hard, using the original observation date and the Stelle Doppie published period and apparent orbit. Also the spreadsheet allowed for comparing the observed separation with the Dawes or Raleigh resolution limits. This was displayed as a computed ratio of observed separation to limit (Dawes or Raleigh). This is shown in the screen shot below with the ratios columns highlighted in color.
This shows 35 double star observations with the smallest resolution limit ratios. The entire list of sub 2 arc-second separations contains some 85 observations. From these it could be seen that for the larger apertures (10- and 11-inch) there were none that came up against the resolution limit for that aperture. Only for my home-made 8-inch Newtonian and the little AT115EDT refractor were there observations that met or exceeded the limit. I suspect that the seeing wasn't good enough to allow the larger apertures to resolve at the limit.
When I added another sheet to contain the close doubles, I had to re-learn how to do the data sorts (by column headings). Also it was handy to have the column headings remain visible at the top when scrolling down then list. These two embellishments were made using the Data Filter and Windows Freeze Panes menu items. It was important to save the entire spreadsheet before making these changes. That way if the something bad happened that scrambled the data, I could just close the spreadsheet without saving the changes.
The red triangles in the Date column indicate a comment attached to that date, which records observing site and observing conditions like seeing & light pollution. While there could be some errors in my correcting the separations to the date of observation, I hope you enjoy perusing these close double star observations. Any comments or suggestions would be appreciated.
Edited by Rustler46, 12 February 2019 - 09:16 PM.