The Half-Astrophysicist Blog

The ISS Joins Fireworks in the Sky

I have been negligent in blogging but want to get back into the groove. As luck would have it, the International Space Station (ISS) is making a series of bright passes over the United States for the Fourth of July weekend.

You don’t need a telescope to see the ISS as it is frequently the brightest object in the sky. You just need to know where and when to look.  My favorite site is Heavens Above.  You can type in your city name, zoom in on your location on a map, or enter your latitude and longitude. You will then be presented with a screen that has customized information for your location. Click the 10 Day Predictions for the ISS and you will see when and where to look.  At this time of year in the northern hemisphere, you can sometimes get two or even more passes per night depending on how far north you are. Heavens Above has a nice free app for Android phones you can check out as well (don’t know about iPhones for sure).

Heavens Above also gives you the magnitude, or brightness of the pass.  On this scale, smaller numbers mean a brighter pass.  A -1 is brighter than a 0, a -2 is brighter than a -1, a -3 is brighter than a -2, etc.  For reference, the brightest star in the sky is Sirius at -1.44. I get a -3.5 tomorrow night, so that is significantly brighter than the brightest star in the sky!

Simply go outside at the appointed time and look in the appropriate direction.  Heavens Above gives the elevation above the horizon to look (in degrees). There is a simple trick to estimating elevation: the diameter of your first held at arms length is about 10 degrees. If you want an elevation of 20 degrees, that is about two fists above the horizon.

The ISS is a very steady light (as opposed to the blinking lights of planes) with a distinctive pale yellow color.  Once you see it a couple of times, you will be able to pick it out very quickly.  Most satellites have similar colors since they are all illuminated by sunlight!

I would love to see a pic of an ISS trail with fireworks in the foreground. Unfortunately, the pass on the 4th of July here takes place at 8:38pm, well before the fireworks start. If anyone can figure out how to pull off a pic like that, please post it!


July 1, 2011 - Posted by | Observing

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