“Splitability” for double-star observers

Recently, one of my AstroPlanner users, Wilfried Knapp, posted this message:

On the CN DSO forum is a rule of thumb for splitting double stars in discussion: Multiply delta-m (if less than 1 then set 1) with the Dawes limit of your scope to get the minimum separation you need to split this double star under otherwise excellent conditions (seeing etc.).

This rule would be nice if available as wizard or better as option when searching double star catalogues.

This seemed like a perfectly useful and easy-to-implement way of rejecting double stars that will not be splittable through a particular telescope, even under perfect conditions. So I decided to integrate it into V2.1.

This feature is available in four places.

Object list

A new “Split” column is available. If the object in the list is a double star, has both magnitudes and a separation listed, and a telescope is selected, then the column will contain “Yes” if the components are splittable according the above criteria.

Object list

In the above example, ADS1, 2, and 5 are all “splittable” using the selected 102mm telescope. ADS3 and 4 are not.

Catalogue display window

In the catalogue display window, if the catalogue contains any double stars, and the Magnitude, Magnitude2 and Separation fields, then a “Split” column is added for the currently selected telescope. Bonus: I also added the Difficulty Index (DI) where that is applicable.

Cat display window

Plan Creation Wizard

The Plan Creation Wizard will now use the above “splitability” test when selecting suitable double stars. It will use the largest aperture telescope you specify to perform the test. Any chosen doubles will be splittable with that largest telescope.

Search Catalogue/s dialog

When manually searching catalogues using the Search Catalogue/s feature, the dialog now includes an option to restrict double selection to those splittable by the specified telescope.

Search catalogue dialog