learned the meaning of the date

Greg responded to my query about the dates associated with some double stars in SkyTools, using Gamma 2 Del aka STF2727A as an example.

Some stars, such as this one, are long period binaries.  Orbits have been computed for them, and SkyTools uses the orbit to estimate the PA and Separation for any given date.

Note on the Object info, just above where it displays the current PA and Sep, it says:  Preliminary Orbit:  P=3249.0 yr, a=10.22"

That tells us that there is an orbit, although it is not definitive yet.  The orbital period is 3,249 years, which explains why it's still preliminary.  In a millennium [or] so it should be more definitive.  :-)

Helpful as always.

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I relayed this info to Dave Cotterell and Malcolm Park.