Bill's Outback Rho

22 April 2019

You can do this!

Here's a photo I've brought home from outback South Australia. It's Rho Ophiuchi, taken using a Pentax K3-II and an ancient Takumar 85mm f/1.8 screw-mount lens built in about 1972.

Rho Ophiuchi is one of those parts of the sky that everyone wants to photograph, a bit like the Great Nebula in Orion. It's not easy, though, mainly because it's so big, but also because you need a seriously dark sky.

The second part we had. Wow. Absolutely zero light pollution - the closest electric light was over 32km away. At 2:45am on the 12th of April the moon had set and the sky was alive. Using averted vision, you could actually see the dust lanes of Rho Oph without any aid.

These dust lanes are incredible. My photo shows them to an extent, but with a 20 second exposure it's never going to be fantastic. A better result would have needed a more time, say 3-5 minutes, which in turn would have required a tracking mount, such as a Sky-Watcher Star Adventurer (or my NEQ6, I guess...).

Because I couldn't take much stuff in the 4WD (and what I did take was going to have the stuffing shaken out of it), I didn't do any of this. This is a single exposure: 20 seconds at ISO 3200. I did use my Pentax's Astrotracer facility to minimise star trails.

Just a camera, a fast lens, a tripod, and a dark sky. You don't need expensive equipment.

The bright yellow star is Antares, which is in the middle of Scorpio. The star to the right and slightly below Antares is called Alniyat II (Alniyat itself is the one diagonally up and to the left of Antares). The blob up and slightly to the left of Antares is the Crab Globular Cluster.

If you want to view this, rather than take a photo, what sort of telescope would I recommend? The dust lanes are big, so in this case magnification is your enemy! It'd have to be a scope with a very short focal length, but a wide aperture. I'd suggest the saxon 1206 or 1025 refractor. If it's for visual use it wouldn't matter what type of mount you use.