BNGC 16. Rich & Poor, Black & White, North & South, Hot & Cold

By Steve Mencinsky, 1994

Astrophotography and the curse of the Northern Hemisphere bias have given a much confused and inaccurate picture of the border between what is visually observable and what is not. To see a good example bf this, one has only to glance at the anguished squirming and straining of the eyeballs (and, let it be said, imaginations! ) at Ilford as the very well known Corona Borealis galaxy cluster (Abell 2065) is minutely scrutinised. And for what? Perhaps at most a half dozen of the faintest of faint fuzzies. In this month's BNGC, your correspondent presents the far less famous yet enormously more rewarding Abell 1060, aka Hydra I.

Your correspondent first observed this wonderful congregation from the [then-new] "unofficial" observing site at Mt White with his [then also-new] observing companions from the Astronomical Society of the Central Coast. For the noncognoscenti, the Mt White site lies some 16km north of the Hawkesbury River and about 3km south-east of the freeway exit of the same name. Despite the recent bushfires which have totally devastated the immediately surrounding area, the now "Mt Black" remains to this day a viable observing area, even if (for now) somewhat less physically attractive than before (bare trees, no undergrowth, no kangaroos, no possums). But life is indomitable and opportunistic; the signs of regrowth are omnipresent and unmistakable.

Even on this first occasion, on which the observing chart was Uranometria Map 325 with only a handful of other galaxies hastily drawn in, it was clear that this was rich territory.

The first impression one receives - and that through the finder - is the wonderful colour contrast of the blue and yellow guide stars (the two brightest stars drawn on the chart, near NGCs 3315 and 3314 respectively). Immediately after this one notices the ragged line of bright galaxies NGCs 3308-9-11-12-14 at an oblique angle to the line joining the two stars. But it is not until the high power eyepiece is brought into play that the field comes to life with a swarm of small and faint galaxies slowly making its appearance. The chart ultimately used was a photocopy of the photograph in the ESO book itself (fortunately, a negative print!). After about an hour of such observing from Ilford, during which the number of successes in the area climbed steadily, your correspondent took the opportunity to take a coffee-and-chocolate break. He noticed with amazement an almost l00% hit rate: almost every arrowed galaxy on the area of chart under attention had now been circled. It had become too easy, this was no longer a challenge; interest was lost immediately, attention and the telescope were moved elsewhere.

The chart shown here shows all the galaxies that were successfully observed at that time. In contrast with previous charts, because of the number and small sizes of the galaxies observed, a different code has had to have been adopted: the circles (open or closed) represent the galaxies, drawn at approximately the correct observed size, with the stars drawn as crosses. Much of the area of the ESO photo remains as yet unobserved by your correspondent; the photo indicates that there are still opportunities galore here.

Clearly, with a telescope such as Johannes - or the Society's 17.5" - a more complete observing session could make distinctly possible having the number of successfully observed galaxies reach the heady realms of the three-figure mark. In terms of visual amateur observation, then, this would make this galaxy cluster a worthy peer of such notables as Virgo, Leo and even mighty Centaurus, and definitely ahead of even Fornax-Eridanus and Grus.

Which brings us back to the opening paragraph. Contrast what is offered here with the miserable scraps of what can be seen in Cor Bor. And yet Cor Bor is (undeservedly so, in your correspondent's opinion) more widely known and certainly more widely observed. It is the joy of unexpected finds such as these that gives BNGC observing its zest and thrill that makes the cold nights slaving over a hot chart worthwhile.

Finally, a note to Joe, David and Chris. Despite the comments in the first paragraph, we visual observers couldn't get by without you. How else would we have our guide charts?