Roaming the Deep Sky #17
NGC 1502
By Don Clouse
The winter Milky Way sweeps from Cassiopeia all the way to Puppis before being lost in southern skies. With good horizons and dark skies, the entire arc of the winter Milky Way should be visible during January evenings before midnight. One of the many galactic star clusters that inhabit this stretch of the Milky Way is NGC 1502 (RA: 4:07.7, Dec: +62:20). It is located 3,000 light years away in the constellation Camelopardalis on the outer portion of our Local Spiral Arm while we are farther back on the trailing end of the arm. Or, it may be that NGC 1502 lies between our spiral arm and the next one out, the Perseus Spiral Arm. The cluster’s location on the sky is shown in the accompanying MegaStar chart (click here for chart). Portions of Cassiopeia and Perseus are shown for reference.
I observed this open cluster at the Twin Lakes Star Party in October, 2000. I used my Celestar 8, an f/10, 8" Schmidt-Cassegrain telescope. With it, I used a 15mm Panoptic eyepiece yielding a half-degree field of view and 135x magnification. NGC 1502 is a lovely, bright (magnitude 5.7), large open cluster. Although variously catalogued at 7’ to 8’ in size, I estimated it to be 10’x6’. About 30 stars of varying brightness were visible is this area. An east/west line of four close pairs or doubles dominates the cluster. This line itself is dominated by the wide (18" separation), bright, central double star Struve 485 – easily the brightest two stars in the cluster. Both members of Struve 485 are seventh magnitude stars of spectral type B0. The northwest star of this pair is the variable SZ Cam, varying from magnitude 7.0 to 7.3.
NGC 1502 is circumpolar at the latitude of Louisville, KY and southern Indiana. It does, however, get quite low on the northern horizon, which, of course, is not the best time to view it. The best time to observe this cluster is perhaps when it is high in the northwest, that is, if you use a fork mounted Schmidt Cassegrain telescope (SCT). If you use a manual SCT as I have, this viewing angle is vastly superior to summoning your (limited in my case) abilities as a contortionist in order to attempt to locate an object high in the north! Look for Camelopardalis high in the northwest during the early morning hours in mid-fall, within an hour two of midnight during the winter, and in the early evening in late winter through mid-spring. For those using dobsonian-mounted scopes, culmination occurs in the pre-dawn hours in early autumn, after midnight late in autumn, and during early night in the winter. The accompanying chart shows stars to seventh magnitude. It may not be sufficient for star hopping. However, the following method may work for locating the cluster. NGC 1502 marks the southeastern terminus of an asterism known as Kemble’s Cascade. In this image Kemble’s Cascade (a.k.a., the asterism STAR 3) cuts diagonally across the center of the picture to NGC 1502 in the lower right. This stream of eighth and ninth magnitude stars extends northwest from NGC 1502 for 2.5 degrees. It should be fairly easy to pickup by sweeping binoculars through central Camelopardalis or simply by sweeping north of Perseus. A few of the brighter stars of this lovely cluster should be visible at the lower end of Kemble’s Cascade as seen in this image by Don Tabbutt. Then try pointing your finder at the same spot. Who knows, it might even work! Enjoy the view. Clear skies and happy hunting!
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