Alpha Piscium (Alrisha): A Binary to Test Your Scope and Eyesite

Best viewed in late autumn, Alpha Piscium is a binary star in the constellation Pisces and is 151 light-years away from us. The two stars in this binary system are named Alpha Piscium A and B. On some star apps or charts, you may see the name Alrescha associated with the star Alpha Piscium A. Alrescha, a word for “cord” in Arabic, is the traditional name for this star system.

Compared to many of the popular double stars I’ve recorded on this site, Alpha Piscium A and B are difficult to separate in a telescope. This is so since the stars only have an angular separation of 1.8″ (referred to as arcseconds). Unfortunately, backyard astronomers with smaller scopes (say under 4 inches) may be challenged to see the stars as two clear objects.

The good news is that splitting binary stars can be an enjoyable challenge and a test of one’s skill and equipment. It’s best to view close binaries like Alpha Piscium when the skies are crystal clear and optics are cooled down since heat will create image distortion.

My Observations

I’ve struggled this evening to get a good, stable look at my targets. Wispy high clouds appear and disappear — almost magically — at various places in the sky. Still, I’m glad to take my first-ever look at Alpha Piscium.

When the scope first landed on the Alpha Piscium, I didn’t think I landed on the correct star. At 18mm in my 8-inch scope, the star doesn’t appear even elongated (or at least under tonight’s sky conditions). I added a 2x Barlow, and now I see two distinct stars; however, the atmospheric conditions have them blurring in and out—so much so that it’s tough for me to focus and concentrate on the stars.

So, I’ve removed the Barlow and put in my higher-quality 12mm eyepiece. I can see a very thin line separating the two stars. Plus, I’ve removed the quivering view I experienced with the 2x Barlow. For now, I’ll enjoy the pair this way, but I plan to return when the skies are friendlier.

Regarding the star colors: I’ve read the stars may appear a pale blue or green due to their close proximity. However, both look white to me.

Key Stats

Constellation	Pisces
Best Viewing	Winter / Early Spring
Visual Magnitude	+3.8, +5.1
Absolute Visual Magnitude	+0.49
Distance from Earth	151 ly
Separation	1.8″ | 208 AU
Orbital Period	3267 years
Milky Way Location	Orion Spur
My Viewing Grade	C+

Sources and Notes

Banner shared under the Creative Commons Attribution-Share Alike 4.0 International license. Photo by David Ritter. Details here.

Sketch by Wayne McGraw

AKA: SAO 110291, 113 Psc, HD 12447