MIzar

I have just gotten back from a scheduled HAL Star Party at Alpha Ridge Park. The company alone was worth the drive out there, although the conditions were marginal at best. I kept waiting for Jupiter to make its appearance, until I realized that what I thought was just unusually bad light pollution to the east was actually an impenetrable cloud bank. No Jupiter. High, thin clouds over the rest of the sky drowned out all but the brightest stars no matter where you looked. Frustrated in looking in other directions, I finally settled in on the Big Dipper, which was in the darkest part of the sky this night.

I slowly scanned the sky from star to star making up this most famous of asterisms, until I came upon Mizar and Alcor. Ahh.. finally, the gods were smiling upon me. I must have observed this beautiful stellar pair for a good 20 minutes or so. With enough aperture Mizar is, of course, amongst the easiest of double stars to split, and although due to the conditions I had only bothered to set up my 60mm Stellarvue refractor (my smallest scope), I enjoyed to the utmost what was still possible to do. Using my 24mm Televue Panoptic eyepiece, Mizar could just barely be split, but it was easier than easy with my 9mm Nagler.

There was Mizar, clearly two separate stars. Alcor remained one. However, going to the googles, I learn that this system is far more complex than meets the eye. Mizar, although we amateurs can see only two stars, is actually four, whilst its (apparently) solitary companion Alcor is itself a double star. Six stars instead of one! What really fascinated me, however, were their colors. They seemed to change from moment to moment. Mizar's four components appeared in my eyepiece as two stars, one big and bright, and the other considerably dimmer and nestled right up against the brighter one. At first, the brighter looked white and the dimmer somewhat orange. But examining them again after a few minutes, I thought they looked blue and yellow respectively, not unlike Alberio. But after a bit, they appeared to swap colors - and then back again!

Now I know perfectly well that all these mutations are quite subjective - occuring in my eye, and not in the stars themselves. But to me, that just intensifies my interest in how we stargazers perceive color through our eyepieces, and reminds me that we should not be dogmatic about what colors are "out there".

FOOTNOTE: It's been almost 24 hours since I wrote the above, and now I'm wondering whether the shifting colors were a result of chromatic aberration. The seeing was frankly awful and I was using a particularly small aperture last night. Perhaps the "action" was going on, not in my eye, but in the eyepiece. I wonder. Would the colors have appeared steady had I been observing with my 102mm refractor, instead of my 60mm?