Jabbah (Nu Scorpii) -- Double-Double Star in Scorpius
The Scorpion’s Double-Double
Jabbah (Nu Scorpii) is a double-double star, but one that will take a bit more effort to
see than the more famous double-double in Lyra. Seeing it as a single double star is
easy since the A/B-C/D separation is a wide 41 arcseconds. Splitting the C/D couple
requires upping the magnification a bit, but at 2.3 arcseconds it is doable even under
poor seeing conditions. However, splitting the A/B couple requires a steady
atmosphere, high power and decent optics. Most sources put the separation of the
A/B couple around 1 arcsecond, but when I made the drawing, my gut was telling me,
that it was a bit over the stated 1 arcsecond. Still to cleanly split the A/B couple is a
challenge. My 155mm refractor has a Dawes Theoretical Limit of separation of 0.75
arcseconds, but it is rare that I can get a steady enough sky to equal or break the 1
arcsecond limit. On the morning of April 14, 2018, there were a few thin high clouds
overhead, but the atmosphere was steadier than I had seen it so far this spring. Often
the A/B couple appears as single elongated star at high power, but this morning, I
could split it at 312x magnification. Nu Scorpii, is a seven-star system, but the other
three stars are not seeable through my telescope. A quick drawing was made on
Jabbah before swing the telescope towards Mars (my real target for the morning).
see than the more famous double-double in Lyra. Seeing it as a single double star is
easy since the A/B-C/D separation is a wide 41 arcseconds. Splitting the C/D couple
requires upping the magnification a bit, but at 2.3 arcseconds it is doable even under
poor seeing conditions. However, splitting the A/B couple requires a steady
atmosphere, high power and decent optics. Most sources put the separation of the
A/B couple around 1 arcsecond, but when I made the drawing, my gut was telling me,
that it was a bit over the stated 1 arcsecond. Still to cleanly split the A/B couple is a
challenge. My 155mm refractor has a Dawes Theoretical Limit of separation of 0.75
arcseconds, but it is rare that I can get a steady enough sky to equal or break the 1
arcsecond limit. On the morning of April 14, 2018, there were a few thin high clouds
overhead, but the atmosphere was steadier than I had seen it so far this spring. Often
the A/B couple appears as single elongated star at high power, but this morning, I
could split it at 312x magnification. Nu Scorpii, is a seven-star system, but the other
three stars are not seeable through my telescope. A quick drawing was made on
Jabbah before swing the telescope towards Mars (my real target for the morning).