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» Live images of Venus Transit «
If you happen to live in certain parts of central Europe, June 8 is going to be a very special day for you. Not only will the transit of Venus across the Sun be visible, but also for a privileged few, the International Space Station ISS will make a daytime appearance, zipping across the solar disk in the blinking of an eye.
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Caught in action by Tomáš Maruška with help of predictions by www.CalSKY.com − ISS/Venus simultaneous transit over Slovakia! |
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From within a narrow corridor stretching from Southern Spain, right through Central Europe and beyond, ISS will manifest itself as a small, fast moving object. Should you position yourself to the north of the viewing centre line you might even be lucky enough to see the station make a simultaneous transit of both Venus, and the Sun (see image generated by CalSky.com). A once in a lifetime opportunity!
Whilst it will be possible to view the dark silhouette of Venus against the solar disk with the naked eye, through a solar filter, catching ISS will require slightly more sophisticated equipment, but nothing beyond the capabilities of most backyard skywatchers.
The main requirement is a small telescope, which will project the full disk of the sun onto a screen of some description... a piece of white card will do. Alternatively provided both view finder and aperture are covered with a professional solar filter, the event can be viewed through the telescope eyepiece.
Safety is an important factor here.
| NEVER LOOK DIRECTLY AT THE SUN WITH UNPROTECTED EYES - THIS MAY CAUSE TOTAL BLINDNESS WITHIN SECONDS! ALWAYS BE SURE TO USE PROPER OPTICAL FILTERS TO PROTECT YOUR EYES. NEVER LOOK DIRECTLY THROUGH A TELESCOPE TOWARDS THE SUN, EVEN WITH FILTERS (ONLY PROFESSIONALS WELL VERSED IN THESE MATTERS MAY DO SO)! FOR OBSERVING THE SUN WITH UNPROTECTED EYES USE SAFETY FILTERS ("SOLAR ECLIPSE VIEWERS") FROM E.G. AN OPTICIAN. ALWAYS BE SURE TO USE PROPERLY CERTIFIED PRODUCTS! |
So, you have the telescope, and are eager to see ISS, what next? Here are a few hints and tips about how to go about it.
First of all, you will see nothing of the station unless you are positioned within the magical corridor.
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CalSKY.com will keep you informed of the precise locations as June 8 approaches (there are suitable locations from South America to Japan). At present, we have a good idea of the track ISS will take. Check here for the ground track to find your nearest location.
When viewing ISS solar transits, preparation is everything! The transit will take less than a second. There's no margin for error.
If you need to travel to get within the corridor, carry out some research first to make sure the location you are heading for is suitable. I usually do a dummy run the day before to make certain that the chosen site is relatively flat, free of tall buildings, trees and anything else that could get in the way of a clear line to the sun. In addition, you may need to set up your telescope on private land. If that is the case, obtain prior permission from the land owner.
Having chosen your viewing site make up a check list of things you will need to take with you.
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Telescope, spare batteries for the tracking drive. Full aperture solar filter for the telescope, and also a smaller filter for the view finder (you'd be surprised how many skywatchers have damaged their eyesight by using a filter on the front end of the scope, but forgetting about the viewfinder!). GPS is a must because wandering off centre by just a few hundred meters could mean missing the event completely... as I have found to my cost...
If you don't have a GPS unit, then before leaving home, log onto Calsky.com and use the "Mapit" facility to create a highly detailed map of the target site (based on MapQuest maps). Print this out and take it with you. You will need to be as close to the red star, marked on the map, as possible.
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Also ensure you take a good timepiece having noted down the exact time of the transit by ISS. Synchronise the timepiece to a reliable time signal! Venus will take about 6 hours to move across the surface − ISS less than a second.
Finally, if you are intending to record the event, a suitable video camera/webcam and laptop (Battery fully charged) will be needed. That's quite a list, but then this is a spectacular event!
Having located the site, on arrival check again to ensure that you are safe to set up. A motorway hard shoulder isn't the best place to choose, nor is a field full of farm animals!
You might wish to spend the whole five hours at the location, or alternatively, just the period around the ISS transit. Either way, its important to give yourself enough time to prepare and check all the equipment is working properly.
I would suggest a minimum set up time of one hour, especially if you intend recording the transit to video. Time goes very quickly when you are working in strange surroundings and the last thing you want is to miss out on the experience because you lost track of those vital last few seconds.
Place the solar filter in front of your scope and finder scope - carfully check for correct placement. For safety reasons many GoTo telescopes will not track the sun. However on this occasion simply "GoTo" Venus. Each telescope will have its own set up procedure. Make sure you follow it religiously. This will ensure perfect tracking.
Test your camera. Ensure you can operate at a minimum of 10 frames per second. Focus on the sun. Ideally, adjust the field of view to show the full disk. I always look for a sunspot cluster to make final focus adjustments.
On June 8 Venus will present a nice dark spot to focus on. Set exposure so that the sun has a good pearly white texture with no areas over exposed.
Check the time.....those minutes are ticking away.
Once you are happy everything is running smoothly... relax. Try to take in the atmosphere around you. Focus your mind on the task ahead.
About two minutes before the satellite transit is due, turn on the camera and leave it running. Make sure the picture on the laptop screen is satisfactory... and that the sun is still nicely in frame.
If you are not filming, but simply viewing through the telescope, try to adjust your eyes to the eyepiece. Become accustomed to the suns image. If need be, make that final adjustment to the focus... carefully! If using the projection method, onto a piece of card, secure the card at the focal point to make sure it doesn't blow away, or fall over.
It's at this point, with just seconds to go, the mind starts to play tricks. You begin to question your judgement... am I really in the right place? is that image slightly blurred? have I really switched the camera on? Don't panic... stay with it, ignore those little voices in your head!
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Suddenly............... zzzzzzzzzzzzzzip it's all over, the tiny shape of ISS streaks across the sun. Spectacular! It is one of those experiences you will never forget... and if its all on video you can hopefully watch it over and over again.
In the run up to June 8 why not familiarise yourself with what to expect. On my website I have compiled a number of transit videos and relate some of my experiences whilst chasing ISS solar transits across the English countryside.
Good luck, be careful, and most of all, have fun.
John Locker, UK
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