Saturday, 26 May 2012

How to image a satellite with a telescope

I hope you all enjoyed my last post on how to image a satellite using the long exposure method, this time its time for method 2 how to image a satellite using a telescope. The things you need to image a satellite using a telescope are camera ( it will need a camera adapter so that you don't have to hold it) or webcam, a dobsanian or alt az telescope (you could try with an equatorial but it would be allot more difficult), and preferably a compass as well. The first thing you will need to do is visit the heavens above website and find out when the next  ISS pass is and what direction it comes from,  you can image other satellite but its best to start with the ISS as it is really big so you should be able to make out some detail on it. On the night that the pass is due over you need to to take your telescope and camera outside about an hour before the pass is due to let them cool, you then need to align your  scopes finder perfectly. About 10 minutes before the pass you need to loosen all the locking bolts on your telescope and point it in the right direction using you compass. Also you need to set your camera to the highest frame rate possible to stop and motion blur.  For your first pass you might want to use quite a low magnification to keep it in the field of view easier, then use the higher magnifications once you've had a bit of practise. Then about 1 minute before the pass is due you need to start recording with your camera or webcam. As soon as you see the ISS coming over the horizon you need to start tracking it with your finder scope ( a non magnified finder is best for this) , it will move very quickly across the sky so it will be hard to keep up with. Once the ISS has gone over the horizon you can now see what footage you managed to capture, your video will mostly contain a lot of empty frames and only a couple of ISS frames ( with practise you will manage to get more ISS frames in one pass.

Now that you have your video file you need to get rid of all the empty frames using virtual dub there's a tutorial for people who haven't used it before: tutorial, now you will be left with a very short movie file with only frames of the ISS in it, but you will have noticed that the ISS jumps around a lot in it.The next step is to process are video file using a program called castrator all you have to do is put in the video, select the brightness and the video size and it will then create a video file for you with the ISS in the centre of every frame. You can now either just use an individual frame for your image or you can process it in registax, you process it just like a video file of the moon. You will now be left with a single image which you can process in any software that you us for your other astrophotography images for instance photoshop. Once you have finished this process you will have your own image of the ISS. With practise you will be able to improve the image, if you have any questions feel free to contact me. Post any comments or tell me about your satellite imaging attempt below.
Part 1 is here.

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