Saturday, August 20, 2016

imaged NGC 457 (Halifax)

BGO imaged NGC 457 for me. Also know as the E.T. Cluster (or The Owl or Caldwell 13). An open cluster in Cassiopeia. One of the RASC Finest NGCs.

RASC Finest NGC aka The ET Cluster luminance

Luminance only, 60 seconds subexposures, 10 stacked shots. FITS Liberator, GIMP. North is up; left is east.

SkyTools shows it is full of double stars...


The bright star is, in fact, φ (phi) Cassiopeiae. aka 34 Cas and H III 23 (William Herschel's group 3). A quintuple system! The second brightest star is HD 7902 or the C star of phi. Between A and C, equally spaced, nearly the same magnitudes, are two faint stars. The one closest to A, or to the north-east, is B. You'd think the other star would be part of the system. Nope. Just some random star. SkyTools 3 Pro says it is GSC 03681-1653. Beyond C, opposite A, is E. Not quite inline. And much brighter than B. D, curiously, is well away, to the WNW of A. It looks to be about the same magnitude as E. [ed: Found it in my View Again list in ST3P—removed it.]

Beyond φ D is a tight group of bright stars, some brighter than D. This is ES 408. This is an 8-star system. I cannot split A and B in the image but A is not completely round. C, oddly, is way off to the north-west. C looks to be a similar brightness to A. D is to the east of C, merged, but dimmer, so making a dog-toy shape. E is to the north-east of A, close, and also about the same magnitude. F is a dimmer star to the south-east of E. Compared to ST3P, it appears to be moving, to the south-west. G is east of A. Dimmer. It also appears to be moving, north, this time. H is beyond F, opposite E. Same brightness as G. [ed: I think there's a glitch in ST3P as I cannot select the A star directly.]

STI 1564 is a touching pair of nearly equal stars to the east of ES 408 C. Perhaps A or B or both have moved a lot...

Finally, STI 1560 is a wide pair of equal stars north-west of ES 408 C.


Processed in colour on 22 Aug '20.


Wikipedia link: NGC 457.

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