Preparing to photograph the ISS

I have to say, the International Space Station is an engaging photographic subject. Hundreds of miles above the planet traveling at 17500mph it wouldn’t be the first thing you’d think of nipping out with the camera to capture. However, once you figure out roughly where it’s coming from, what you’re looking for and when it’ll be there it’s almost addictive.

If you happen to be on Twitter try following some of these accounts and you’ll be amazed at how many retweets they send out of images after every visible pass over the UK.

@VirtualAstro
@PeoplesAstro
@NewburyAstro

Planning for the ISS makes a huge difference. The @VirtualAstro twitter account is a good place to start, there’s a wealth of info for every pass from that particular source. The website, http://www.heavens-above.com is also good for working out the directions, altitude and brightness of the ISS for any given pass. The free astro programme, Stellarium for Mac or PC is also very helpful, it’ll show you the exact path the ISS will take and from this you can work out in relation to the planets where it’ll be which makes planning a lot easier. The iPhone app StarWalk also allows you to do this.

Here’s a screen dump from Stellarium and from it you can see the ISS path for tonights pass in relation to Sirius and Mars, two of the easier night sky objects to spot.

This is a screen dump from the iPhone Star Walk, from here you can see the ISS and you can advance the time with the bar on the right to watch the path it’ll take over the sky.

Typically the nearer to sunset the longer the ISS will be visible, approx. an hour to 1.5 hours after sunset you’ll get a very bright pass almost from the western horizon to the east later in the night, it’ll disappear into the earth shadow quicker.

So, with this info in mind the temptation is to sit in the house watching the telly and nip out just as it’s about to pass. I’m guilty of it too. But if you apply a little landscape photography principals to the astro info you can totally change the shot you get.

Photographing just the sky is fine, and even better if you can get something significant in the sky to reference the ISS path, i.e. passing Mars, or Saturn. However, get the land in the shot and you’re starting to tell a story with your shot, you’re showing the whole event. The pass of this object over the scene you’re looking at. So tell me whats better here…

The ISS crossing over my back garden, passing just over Saturn

ISS flies over Saturn 14 April 2012
Or this image taken on the Cammo Estate in Edinburgh

ISS over Cammo Edinburgh

The 2nd image took a stack of planning to get. All the info above plus looking at Google maps to find a location with good views to the west, south and east. The only issue I had with this image was the clouds were obscuring Mars so I couldn’t get a reference for how high the ISS would be in the sky, with hindsight I should have used a wider lens but we can all be great in hindsight can’t we?

Using Star Walk I figured out roughly where on the horizon the ISS was going to emerge from and composed the shot to catch it as quickly as I could as it rose, also keeping in mind I wanted Cammo Tower and the copse on top of the hill in the shot. Ground was kept to the bare minimum required and the sky was the main focus.

The sky was still quite light so I went for a balance to catch the ISS. I used ISO320 and f4.5 and limited the exposures to 10s, this gave a nice balance in the shot but meant enough sensitivity to get the light from the ISS.

In the end I got 12 frames of 10s each until the ISS left the field of view, being an early pass I had time to recompose and get another few frames before it disappeared.

The 12 raw images I took into ACR and processed them all exactly the same and saved as jpg files. These 12 jpg’s were loaded into StarStax and blended on lighter mode. This was fine, the ISS trail was night and bright but the cloud movement was nasty and not smooth. To get around this I stacked the 12 images again using the “average” method which gave a much more pleasing image with the clouds but a faint ISS trail. I then blended the first image into this on lighten mode and decreased the exposure until only the bright ISS trail and stars remained. The resulting image was flattened and tweaked in photoshop to produce the final image.

If I were to process again I may patch in the gaps in the trail between the exposures and as a personal preference I would also try to lose the star trails by blending in another image and selectively deleting the trails.

With a location like this though and a nice (nearly clear sky) it’s worth taking time for a few other shots before you back up.

This was a single from from the composite image. Notable objects in the shot are the ISS, Mars, Regulus, Sirius, and Orion.

Mars and ISS over Cammo Tower

In this shot, the ISS can be seen behind the clouds passing just over Saturn and Spica.

Saturn Spica and ISS over Edinburgh

In this final shot taken just after the ISS pass, Venus is nestling on the branches of this particularly creepy tree!

Venus in the spooky tree

A little planning can work wonders, it’s all just about planning and crossing your fingers for the weather to play ball. It won’t work out every night but for that odd one it does you’ll be well pleased you put in the effort.

Get out and look up tonight and for the next few nights before it disappears under the horizon for another few weeks!

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