ISS Solar Transit

Frank Ryan · Post by **Frank Ryan** » Sat Jan 22, 2011 8:24 pm

I photographed the ISS transiting the Sun
from Shannon Airport about a mile West of the centerline for this due to thick fog!
Luckily the weather stayed clear there just long enough to catch the pass.
Not particurally ideal conditions added to the fact that the ISS is about as high as it gets in orbit right now (the distance from my point was 1020.5km!) and the Sun's altitude was only 16 degrees high.
I used a Canon 350D with an f6.3 focal reducer through a Meade ETX-125 OTA manually guided on a Manfrotto photographic mount.
I started the photo run 2 seconds before the predicted transit time and ran 2 seconds after
at 1/1200 sec shutter speed, ISO800 on multi shot mode.
After the pass I scrolled through the shots and found I'd captured 3 seperate images of the ISS moving across the suns disk during the 1.23 second transit.

farm6.static.flickr.com/5288/5377566783_97c7f9b2bf_z.jpg

farm6.static.flickr.com/5050/5377566983_9681045f94_b.jpg

Roy Stewart · Post by **Roy Stewart** » Sat Jan 22, 2011 9:43 pm

Nice Pic's Frank.

You gotta give some of your hints and tips to capture shots like that some day.

Cheers Roy

John O'Mahony · Post by **John O'Mahony** » Sat Jan 22, 2011 9:49 pm

Thats cool Frank. Nice work.

Gordon Lalor · Post by **Gordon Lalor** » Sun Jan 23, 2011 1:48 am

Nice one frank!
I suppose you'll be doing a "Thierry Legault" on it and capturing a lunar transit next?

His solar: http://legault.perso.sfr.fr/eclipse1101 ... ansit.html
And lunar: http://legault.perso.sfr.fr/eclipse1012 ... ansit.html

Did you use http://www.calsky.com to calculate the timings?

Cheers,
Gordon

Frank Ryan · Post by **Frank Ryan** » Sun Jan 23, 2011 8:46 am

Ha. No, not yet as mad as him.
He figured out where this was going to
be visible then went there specially for that
one shot!
Now if I won tge Lotto and had nothing better to do....
Ya I used Calsky.
I've a lunar transit planned for next week.
Its a pity the ISS boosted reciently.
It really makes a difference to the size,
that and the alt of the pass.

Dave Lillis · Post by **Dave Lillis** » Sun Jan 23, 2011 9:27 am

ya, I was thinking is looked a little small.
Nice image, a good start, maybe if you used a camcorder next time, ?

Frank Ryan · Post by **Frank Ryan** » Sun Jan 23, 2011 1:22 pm

It's really a case of luck
and Photographing it when it happens
to be lower in orbit and the pass higher in alt.
That combination would yeild a mucher larger ISS with good detail.

I've 3 seperate shots if it going across
run together as a gif is a nice little representation of the pass.

I've been contemplating using the webcam also alright,
it's only a start as you say,
more fun to be had now I've the set up
the way I like it.

Dave Lillis · Post by **Dave Lillis** » Sun Jan 23, 2011 3:48 pm

a webcam would be very challenging as the narrow field of view would necessitate tracking the ISS directly = hardship !
last time I saw the iss cross the sun it was size of copernicus on the moon, like the size of one of the "ISS" letters. its bloody tiny in your pic.

Frank Ryan · Post by **Frank Ryan** » Sun Jan 23, 2011 4:49 pm

Oops! did I say webcam..
ment camcorder.
I've a new attachemt for it that clips onto the eyepiece for prime photography.
It's a bit of a pain to focus it but works OK.

Yeah it's tiny isn't it!
I was expecting it to be that size as they boosted the orbit almost to the max
there in December
http://www.heavens-above.com/OrbitHeigh ... atid=25544

Plus you know yourself when it's a low pass it's that much further away and
therefore smaller.

The time I got it (and the shuttle) with the webcam:

It passed almost directly overhead (Cork)
and was lower in orbit to facilitate the shuttle docking.

BTW here is a merged shot showing the 3 seperate images in one:

It's all down to luck that you get firstly a transit occuring near you and
then the weather is clear and then the heights are high to get a big ISS.

We're particurally lucky here in Ireland that we get a lot of passes.
What's foiled me constantly is the day of the pass I've either been working or it's been cloudy.

Now that I've cought it and the gear works well I wouldn't be bothered
again unless it was going to be lower in orbit.
Same go's for the Moon although I still want to test the gear next week on the upcoming lunar transit.
After that.. it's a case of playing the waiting game.

Conn Buckley · Post by **Conn Buckley** » Sun Jan 23, 2011 9:29 pm

Lovely job Frank, I enjoyed that. It sounds like it was great fun to do and I suspect a fair bit of planning went into capturing this image. Did you have any prior info on ISO/shutter speed settings before attempting this? I did not realise that the predictions were that accurate. Does the prediction give the ingress/egress times? I reckon that had to be a tiny amount of time.
Just a thought .... have you considered submitting this image to the local newspapers?

Frank Ryan · Post by **Frank Ryan** » Mon Jan 24, 2011 5:37 am

To be honest no.
I think Joe Public would want the ISS
much bigger to 'get it'
Although APOD have used similar size wise;
http://apod.nasa.gov/apod/ap050729.html

Ya, a fair bit of preperation go's into it.
Not an insane amount mind.
Very similar to a Solar Eclipse in the sense
that you have to be at the right place at the right time, gear set up and tested and timer set. You only get one chance at getting it.
I didn't research camera settings before hand
as there is no golden rule.
Obviously enough you need to have a very fast shutter speed combined with iso setting to catch any bit of detail and not an oblong blob.
sunspots help hugely.
for this and for focus.
BTW when looking for a spot to take this on Google Earth I found a cool place for observing right at the back of the Airport.
Its right at tge end of the runway.!
The planes fly directly over your head only a few hundred feet above!!

Also, on timibgs, yes it's that accurate.
You need to get the Calsky download a few hours before your shot becaus they make adjustments noe and again.
Enough to kick it out of the transit.
The pass duration is predicted and
from that you can work out shutter speed to maximize chances of catching it.
It's all great fun!

Heres a video of the pass you might like,
gives you an idea of the speed your dealing with
http://www.youtube.com/watch?v=bJ3LwAaF ... ata_player

Roy Stewart · Post by **Roy Stewart** » Mon Jan 24, 2011 2:01 pm

Hey Frank.

Is there any chance you can bring some red film to cover over my head torch at the next meeting.

Cheers Roy

Frank Ryan · Post by **Frank Ryan** » Mon Jan 24, 2011 3:51 pm

Conn Buckley · Post by **Conn Buckley** » Tue Jan 25, 2011 11:03 am

Frank, thanks for sharing the 'how to' info. I can see how valuable the sunspots were. The video nicely captures the very, very, very short transit and ergo the shutter speed calculation.
Was the airport site chosen because of the triangulation of you, ISS and Sun positions? In other words was the transit not visible from your back garden? I can well imagine that a guy at the end of the runway with all the gear you had set up might attract the wrong attention.
Just think if a small plane had taken off before the end of the runway and turned between you and the Sun .......... !!
Looking at the APOD by Anthony and with a better understanding of how this image was captured confirms just how good your result was. Well done again.