Object: iota Cancri

Magnitude A / B / C
Separation A-BC/ AC
Position angle A-BC / AC
Spectral class A / B / C
Colour A / B / C
: Cancer
: 08:46:42 / +28.45
: 4.1 / 6.57
: 30.7”
: 308°
: G7.5IIIa / A3
: Orange / Blue-white
Detail sketch:
Date / Time
Observing Location
Seeing / Transparency
Magnification / Field of View '
: 30/03/09 / 21:45
: Landgraaf
: 3 / 3
: Orion Optics UK 300mm
: 22mm Nagler Type 4
: 78 / 68
Iota Cancri

Observing Report

Iota Cancri is a very easy object. In the 300mm the double was already split at the lowest possible magnification of 46x. The contrasting colours of Iota Cancri, orange and blue-white, are at their best at this low magnification. This double definitely rivals Albireo in Cygnus. Now I understand why Iota Cancri is also known as the "spring Albireo".

Anyway, after trying all possible magnifications, I chose the 22mm Nagler with a magnification of 78x and a field of view of 68' as the optimum magnification for sketching Iota Cancri. In the centre you see the orange A component with the blue-white B-component at eight o'clock. The double is very well split. There are no other significant bright stars in the field of view, and there is no other star visible that shows any sign of colour. There are quite a few asterisms, forming triangles and even a little diamond shaped group. To the north of Iota Cancri I see two very faint stars. There are no chains of stars, and between the several asterisms there are dark areas visible. There is no nebulosity involved, and I do not detect a glow of unresolved stars, not even when using averted vision.

Visually Iota Cancri is very attractive and it should be on every ones observing list.


Although Bayer assigned the Greek letters to stars more or less according to the order of brightness within a given constellation, in Iota Cancri's case the Greek letter iota is a bit strange. Iota Cancri is the second brightest star in Cancer, after Beta. Iota however is the ninth letter in the Greek alphabet. There is very little known about this double. Iota Cancri is probably not very well studied. The only information I could find on the Internet was on Jim Kalers website "stars": The A component is a G7.5 giant with a surface temperature of 5000K while the B component is an A3 dwarf star with a surface temperature of 8800K. Iota Cancri is a true binary star, separated by at least 2800 AU and an orbit that takes at least 65000 years to complete.