The International Space Station (ISS) is an awe inspiring sight in the night sky and if you’ve never had the opportunity to see it, then this post should help you out.

The ISS has been in operation for over 10 years and orbits the Earth at varying altitudes but on average stays around 350 km above the surface (although recently the average orbital altitude has been changed to 400 km).  The ISS is roughly the size of a football field and if you are interested, other facts and figures of the ISS can be found here.

You may not know it, but you can see details of the ISS (i.e. its solar panels) with cheap binoculars as it orbits overhead.  Since the ISS travels so quickly across the sky (orbiting the Earth every 90 minutes means it travels around 27,000 km/hour), the best viewing tools are your own eyes and binoculars.  I’ve used my manual telescope (10” Newtonian reflector) to catch short glimpses of the ISS but I have to lead the scope ahead of the ISS path in hopes of catching it across the field of view and this VERY difficult and I only recommend this method for those who are very experienced with their telescope.

So don’t worry about fancy telescopes or huge binoculars when going outside to view the ISS.  Even on the best of viewing occasions, you’ll only have about 5 minutes to see it pass overhead so viewing the ISS doesn’t require a lot of preparation or take too much time out of your busy schedule.

The only site you need to visit to give you a heads up on ISS viewing opportunities is heavens-above.   Register your location at this site and then click on the ISS link to give you times when the ISS will be overhead in your area.  The page for today in my area looks like this:

The table’s 11 columns are self explanatory but I’ll give further explanation if you aren’t familiar with these astronomical terms.

Column 2 is the brightness of the ISS and the more negative the number indicates a brighter view of the ISS.  In the chart above, 11-DEC-12 will be one of the brightest viewings in my area and as I’ll explain below, it will also be the date that will afford the most viewing time of the ISS.

The rest of the chart is divided into three sections – When/Where the ISS first appears, When/Where it will be at its highest point and when/where it will disappear.   The ‘ALT’ column corresponds to the altitude (in degrees) the ISS will be above the horizon and ‘AZ’ is the direction (North, East, South, West).

For example: On 11-DEC-12 the ISS will first appear at 6:37 pm 10 degrees high in the Southwest, will reach its highest point at 6:41 pm 67 degrees high in the Northwest (90 degrees is directly overhead) and will disappear at 6:42 37 degrees high in the North-Northeast.

The total viewing time on 11-DEC-12 in my area will only be about 5 minutes but this is an excellent viewing opportunity because the ISS will be high enough in the sky to be above trees and this will allow me an opportunity to point my binoculars at it.  The 67 degrees altitude will also allow a comfortable viewing with binoculars since I’ll be holding my head about 2/3rds of the way between level and straight up.  Viewing an object at 90 degrees to the horizon always affords the best possible viewing detail (because the object is at its closest approach) but tilting your neck at this angle for too long is uncomfortable and makes it difficult to track a fast moving object with binoculars or a telescope.

You will notice that the ISS viewing times are only at dawn and dusk and there is a good reason for this.  The only reason we can ‘see’ the ISS is because of the sunlight is reflecting off it and this only happens when the Sun is either rising or setting (if the ISS passes over us at midnight the Sun is on the other side of the Earth and therefore its light is shielded from the ISS by the Earth).

One final thought regarding the Heavens-Above site – The ISS is just one of many objects that you can view in the night sky with your naked eye or binoculars.  On the Heavens-Above website, you can find times when other satellites, comets and planets will be overhead in your location and most of these are visible with the naked eye!

You can also check out a previous post which gives you instructions on how you can catch a glimpse of our solar system’s largest planet (Jupiter) this winter.

Take time over this holiday season to go outside and look up!