Southerly Star Trails
I began this image with a single 25 seconds exposure, changed the exposure, then exposed a further 99 exposures at 15 seconds. Hence: bright stars, followed by a short gap then slightly dimmer trailings.
Why? It seemed like a good idea at the time, because I wanted to ensure my Japanese Maple tree was illuminated in the corner of the first frame. Perhaps I shone a torch, I can’t remember, because it was not long enough ago.
The observant reader will deduce from this timing sequence that the stars were rotating clockwise. We do things properly here in the Southern Hemisphere.
You may also notice no obvious pole star. That’s because we don’t have one. Or at least we don’t have a bright one. And it’s not near the pole.
This is all in the southernmost constellation of Octans.
I doubt if there is any other constellation in the sky which is more devoid of bright stars than Octans is. Which used to make it extremely difficult for us southerners to polar align our telescope mounts. Now we have laptop software which does it for us. Easy-peasy.
Polaris Australis (Sigma Octantis) is the brightest star in the central vicinity at an unimpressive +5.44 magnitude (barely visible).
Sigma is the closest bright streak in the 3 o’clock direction, beyond the little triangle of stars at the centre of my image. It is located about 68 arc minutes from the South Celestial Pole, which is of course at the centre of all those arcs.
The above feature image was from the last clear sky here, twenty-five days ago on 6th December. I’m not happy about losing all those evenings under the stars – but this time last year we had already endured many more days and nights of intense bush-fire smoke.
As my Bride wisely asked me, “Which of those two scenarios would I prefer?”
Happy New Year
Very best wishes to all of my readers.
Thanks very much for your visits and comments during 2020.
Let’s hope that in 2021 we can regain our freedom and that our political leaders will show a little more compassion and stop telling lies.
|Camera:||Canon 60D, 50 mm, f/5.6, ISO 250.|
|Exposure:||1 x 25 sec + 99 x 15 sec = 25.25 minutes.|
|Field of View:||Approximately 40° x 27°.|
|Software:||DPP, Star Stax v0.70, GIMP.|
|Observatory location:||34° South.|
Images © Roger Powell
I’m a founder member of Macarthur Astronomical Society