Eyes up! Some bright ISS passes for Canberra this week. Iridium flares too!

Photo by Ashley Kerlin 

It's that time again when we get to look up and see the only place where humans live other than on Earth zipping across our skies. The International Space Station has a number of very bright passes coming up over the next few days—some at fairly family-friendly times (given it's school holidays anyway).

For Canberra people there is a very bright, high and long pass each of the next five nights, including tonight. Anything from this table above -1.5 is quite bright (above being a larger negative number).

It's great fun to try to catch the ISS in a photograph. Set your photo quality to the highest possible (RAW if you have it), your lens to a wide zoom, your aperture small, shutter to 30 seconds or more, prefocus on something as far away as possible and then turn autofocus off. Set your camera on a tripod pointing towards where the ISS pass will appear. Use a wired or wireless remote if you have it, otherwise set the self-timer to two seconds to give any button-pressing vibration time to settle before the shutter opens.

I also like to frame up a foreground object as long as it isn't lit too much. Conversely, if the foreground is very dark, you can 'paint' it during your exposure with a second of light from a torch. Photoshop will also allow you to brighten 'shadows' afterwards to highlight your foreground.


To really nail down where the ISS will appear in your sky, iThing users can download the great little app ISS Spotter.

For added interest, try to catch yourself an Iridium flare. These are extremely bright but very short flashes of sunlight off the very shiny Iridium satellite telephone network satellites:

Wondering what all these brightness figures mean? As they explain on www.heavens-above.com:
The lower the value, the brighter the object, so magnitude -4 is brighter than magnitude 0, which is in turn brighter than magnitude +4. The scale is logarithmic, and a difference of 5 magnitudes means a brightness difference of exactly 100 times. Examples of magnitude values for well-known objects are:

Sun	-26.7 (about 400,000 times brighter than full Moon!)
Full Moon	-12.7
Brightest Iridium flares	-8
Venus (at brightest)	-4.4
International Space Station	-2
Sirius (brightest star)	-1.44
Limit of human eye	+6 to +7
Limit of 10x50 binoculars	+9
Pluto	+14
Limit of Hubble Space Telescope	+30

So those flares going as bright as -7.0 should be something to see...

Clear skies!