Delta Cygni -- Double Star in Cygnus
Delta Cygni marks the center part of the northwest wing of the Swan. The Swan
(Cygnus) has several impressive double-stars. Albireo, 61 Cygni and Delta Cygni
are the constellation’s best of the best. Albireo and 61 Cygni are wide doubles
cleanly split even under low power -- but splitting the Delta Cygni pair is far more
challenging. With a separation by only 2.5 arcseconds plus significant differences
in brightness (magnitudes 2.85 & 6.33), the split may be challenging for telescopes
in the 3 to 8-inch size. Stable skies and moderate-to-high magnification should do
the trick if the optics are good.
Delta Cygni is really a triple-star system, but the third component star is very dim and
not visible with most amateur telescopes. It is also worth noting that Delta Cygni will
be our North Star in 11,000 years thanks to the Earth’s 25,772-year axis wobble.
I see the primary star as white and the secondary also as white, but with a bluish tinge.
Others report colors from green to vivid blue. Whatever colors you see Delta Cygni,
it is a pretty pair and a good optics test for your telescope.