Kappa & Iota Bootis -- Double Stars in Bootes
The 2nd and 3rd Donkey Colts – A Double-Double in Bootes
I still have my first telescope; a vintage Monolux (#4380), 2.4-inch, f15, achromatic refractor. I
saved 6 months of paper route money to buy the telescope through the Sears catalog in the
early 1960s. It is one of the best $100 that I have ever spent. Although small by today’s
standards, it has excellent optics and a well-designed equatorial mount. Through this
telescope, I first saw the planets, moon, sunspots (it came with a projection screen) and all
the other celestial wonders that I could take in from my parent’s backyard in Southern Oregon.
I have long since upgraded the vintage refractor to take 1 ¼ inch eyepieces, but outside of
that it remains the same as when I bought it over 50 years ago. Over the years I have
completed the Messier Catalog using the small refractor – a challenge using only a 60mm
objective lens. I evolved with the hobby, buying bigger and more modern equipment, but the
little refractor never left my side. Currently I have it mounted on top of an AstroPhysics,
6.1-inch, f7, oil-spaced-triplet apochromatic refractor.
The wide-spaced double-double stars Kappa and Iota Bootis, were a fine sight in the small
refractor the morning of January 16, 2019. I still am shocked at how clean and sharp the star
images are in the little Monolux refractor.
Three stars in the constellation of the Herdsman (Theta, Kappa and Iota) are known as the 3
donkey colts. Kappa the 3rd colt (Asellus Tertius) and Iota the 2nd colt (Asellus Secundus)
are pleasing doubles in binoculars or any-sized telescope.
Kappa is really a triple-star system but one of its stars cannot be seen through a telescope
(spectroscopic binary). Both brighter primary stars of Kappa and Iota vary slightly in
brightness (Delta Scuti type variable stars).
These pleasing double-double stars are an easy star-hop from the end stars of the Big
Dipper's handle and awaits for anyone with a pair of binoculars or telescope.