Struve 1678: A Light Yellow Double of Equal Brightness in Coma Berenices

Struve 1678 (STF 1678) is a double star in the constellation Coma Berenices, best viewed on spring nights.

The two bright stars in STF 1678 are wide apart at 37.7 arcseconds and are nearly equal in brightness. These factors make this double an easy target for amateur astronomers. The primary star is a yellow-white sequence star classified as F4V that shines at a magnitude of +7.2. Meanwhile, the slightly fainter companion shines at a magnitude of +7.7.¹

The double lies 188 light years away from us.

My Observations

As I research online for observations on this double, I find contrasting points of view. One person writes “wow,” while another calls the pair “dull.” I don’t really agree with either of these words. Instead, this is a nice, and fairly pretty, wide pair worth checking out. These two stars are very close in brightness, too. The bottom one (at least in my eyepiece) must be the primary as it seems a touch brighter. Also, this primary has a tinge of yellow, while the fainter star is either closer to red or a dimmer white. I’m really having trouble telling the color of this companion star.

Key Stats

Constellation	Coma Berenices
Best Viewing	Spring
Visual Magnitude	+7.2, +7.7
Separation	37.7″
Position Angle	350°
Spectral Class	Primary=K0IV
Absolute Visual Magnitude	+3.87
Distance from Earth	188 ly
Milky Way Location	Orion Spur
My Viewing Grade	B+
Designations	SAO 100235, HIP 62249

Sources and Notes

Banner illustration was created by the European Southern Observatory (ESO) and is under the Creative Commons Attribution 4.0 International License. Per ESO agreement: Here is the original image on the ESO website.

¹Observations of STF Doubles. (n.d.). Retrieved May 6, 2023, from https://mainsequence.org/html/obs/STF_Doubles.html

Sketch by Wayne McGraw