Borg 77mm astrograph – The Amazing Sky

The southern Milky Way is populated by the sky’s best clusters of stars.

Here are three of the southern sky’s best star clusters, in portraits I took earlier this month from Australia.

At top, my main image takes in a great contrasting pair of star clusters. Both lie in the constellation of Puppis, once part of the ship Argo Navis.

At left is the stunningly rich NGC 2477, so packed with stars it almost ranks as a globular cluster, not one of the sparser open clusters. At least that’s the impression it gives in the eyepiece. But instead of containing hundreds of thousands of stars, as do globulars, NGC 2477 “only” has 300 stellar members. They are just very tightly packed in one of the richest open star clusters in the sky. If it had been farther north NGC 2477 would certainly rate as one of the top 100 sky sights, and carry some memorable name after a fanciful resemblance to who knows what! Instead, it carries but a catalog number.

Next to it, at right, is NGC 2451, more typical of open clusters. It has a central bright star, this one naked eye, surrounded by 40 or so lesser stars of contrasting colour and brightness. The two clusters make a great side-by-side comparison in any low-power telescope.

Much farther along the southern Milky Way is this rich open cluster (above), NGC 6067, in Norma, itself embedded in one of the richest star clouds of the southern Milky Way, the Norma Star Cloud. Here you are gazing for 6800 light years toward the cluster which shines suspended against the background of the even more distant inner arms of our spiral galaxy.

So NGC 6067 looks a little like an island of blue stars amid the dust-reddened background of more distant stars in the Milky Way — an island in a sea of stars.

The Carina Nebula glows among the colourful southern stars.

I’ve shot this field many times over the years in visits to the southern hemisphere but never with a result quite like this. Last night the sky was hazy with high cloud but I shot anyway. The result is a “dreamy” rendition of the Carina Nebula and its surrounding clusters of stars. At upper left is the Football Cluster, NGC 3532, while at upper right is the Gem Cluster, NGC 3293.

As with my previous post, the haze brings out the star colours, filling the field with pastel shades. It is one of the finest fields in the sky, worth the trip down under.

Alas, skies have clouded up tonight with only a few bright stars and Mars shining through. And the forecast is for rain for the next few days. So I may get lots of writing done at my Aussie retreat.

As a technical note: I shot this with the little 77mm Borg Astrograph, essentially a 300mm f/4 telephoto lens that is tack sharp across a full frame camera, like the Canon 5D MkII I used here. It was riding on my Astro-Physics 400 mount and guided flawlessly with the Santa Barbara SG4 auto-guider. The image is a stack of four 8-minute exposures. All the gear, much of it stored here in Australia between my visits, is working perfectly.