I NEED HELP photographing the International Space Station

StewartR

StewartR

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Stewart
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If you weren't aware, the ISS is making a number of bright, high-altitude passes over the southern UK this week. (Predictions for my location are here.) So I thought it would be fun to try to photograph it, with ordinary camera equipment rather than a telescope or anything.

But I've been struggling and I think some of my assumptions / calculations must be wrong. I'd be grateful if somebody could look through my reasoning and spot the error.

How big is it?

The ISS measures about 109m by 73m (reference) and its orbital altitide is 413 to 418 km (reference).

I'll be photographing it with my trusty old Canon 40D, which has an APS-C sensor measuring 14.8mm across.

The simple rule for telephoto subjects is that, to fill the frame, subject size / subject distance = sensor size / focal length. So in order to fill the frame I need a lens with a focal length of 14.8mm x 418km / 109m, which comes to 56,756mm.

OK, obviously I was never hoping to fill the frame. Say I use a 300mm f/2.8 with a 2x extender. I can use that hand-held, which will be handy for acquiring and following a moving object. That gives me 600mm of focal length. So instead of the ISS filling the whole 2592 pixels of the sensor, it will cover 2592 x 600 / 56756 = 27 pixels.

What does 27 pixels look like? Well, to get a feel for it I've used a NASA image (here), scaled it down to 27 pixels across, and then enlarged it by 10x to make it easier to see. Here it is:

ISS-1.jpg


I'd be pretty happy if I could do that.

How fast is it moving?

The orbital velocity of the ISS is about 7.66 km/sec according to Wikipedia (reference). I'll be photographing it with each pixel corresponding to 109 / 27 = 4m. So in one second it will cover the equivalent of 7660 / 4 = 1915 pixels.

This gives me two conclusions. Firstly, it will move across the frame in under 2 seconds, so trying to shoot it hand-held sounds like it might be a good idea. And secondly, if I can maintain a shutter speed of 1/2000th or faster, I should be able to freeze it at the pixel level.

How bright is it?

By definition the ISS is only visible if it is in sunlight. And there are no clouds up there, and no haze, so it's going to be bright sunlight. Hence it seems to me that the Sunny-16 rule ought to be applicable.

So, for a shutter speed of 1/2000th, I need f/16 and ISO 2000. Or if I open up the aperture by 3 stops, I get f/5.6 and ISO 250. And let's say I want a extra stop of shutter speed to make sure I don't blur it. So I have 1/4000th at f/5.6 and ISO 500. That sounds achievable.


Before I post any of my results, can anyone spot a flaw in any of my reasoning?
 
It's easier to stick a wide angle on and merge five, 30 second shots to get 1 big line across the sky lol

Had a go at getting it with my big telescope & camera and although it filled the frame more than you've calculated - the closer you go in the harder it is to track (so fast). Would take a few attempts but I'm sure I'd get it in the end.

However there's no way it be tack sharp as even if you got focus spot on, the speed it's moving plus any haze/turbulence in the atmosphere would effect it's clarity
 
Big Andy said:
I'm not going to argue with that Stewart, I will give that a go myself now you've done all the hard work. Thank you.
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Matt-P said:
Thanks for the info - inspired to give it a try when the sky's clear
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Cheers guys. But stay tuned to this channel before you do. As I said there's something wrong with my calculations ... I'm just not yet sure what.
 
buckas said:
It's easier to stick a wide angle on and merge five, 30 second shots to get 1 big line across the sky lol
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Boring. :D

buckas said:
However there's no way it be tack sharp as even if you got focus spot on, the speed it's moving plus any haze/turbulence in the atmosphere would effect it's clarity
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Orbital speed shouldn't be an issue if the shutter speed is high enough. At 1/4000th it's only moving half a pixel (with my camera and lens) whilst the shutter is open.

I don't think haze should be much of an issue. Looking straight up, there's less atmosphere between me and the ISS that there would be for some ordinary landscape shots.

I'm not sure about atmospheric turbulence. But shouldn't a 1/4000th shutter speed eliminate that?
 
I believe but not certain that turbulence has already disturbed the light reaching your camera so shutter speed will make no difference to that problem. I may be getting out of my depth here by the way. ;)
 
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I cannot wait to see what you come back with Stewart, all the best. Have you seen this thread?
 
IF (and the capitals intimate that it's quite a big if!) the sky's clear tonight and I'm still awake enough, I'm intending to head up to a nearby darkish spot with my D800, 12-24 (for long exposures, hopefully catching some Perseids) and superzoom bridge in the hope that I can catch the ISS. Its 720mm long end should get me close enough to see some shape rather than the usual white streak. Hopefully the DSLR will catch the entire ISS pass in one exposure (I've got the expected time so will aim for a minute either end).

Had a look at the weather forecast for tonight and it says "Mostly Clear" but given the Met office's usual accuracy, it'll be persisting down...

Good luck to all trying for a shot - look forward to seeing the results.
 
StewartR said:
By definition the ISS is only visible if it is in sunlight. And there are no clouds up there, and no haze, so it's going to be bright sunlight. Hence it seems to me that the Sunny-16 rule ought to be applicable.

Before I post any of my results, can anyone spot a flaw in any of my reasoning?
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Yup - it's due to pass over at around 23:00 tonight. I think that you need to calculate with a smaller F-stop! :D
 
That's the second pass tonight - first one is (obviously! :nuts: ) earlier.
 
Just watched it go overhead on the first pass - bloody hell that's fast!
 
Well I had a quick go at it only with a 300 on. Tbh It looks like something from that game Galaxian :LOL:
 
DemiLion said:
Yup - it's due to pass over at around 23:00 tonight. I think that you need to calculate with a smaller F-stop! :D
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I think he means it will be daylight from the perspective of the ISS. It's the sun that's lighting the ISS to make it visible.

Still, though. You may be right anyway. Not convinced f/16 will pick up such a tiny amount of reflected light. Could be wrong though.
 
300mm won't be long enough. Even on a 4/3. Failed miserably capturing the ISS in recognisable form on the bridge and failed to take a QR plate to mount the D800 for a wide shot to catch a streak.

There's a word I use but I'm not allowed to use it here.
 
Nod said:
300mm won't be long enough. Even on a 4/3. Failed miserably capturing the ISS in recognisable form on the bridge and failed to take a QR plate to mount the D800 for a wide shot to catch a streak.

There's a word I use but I'm not allowed to use it here.
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I know that and you know that Nod. But after Tweeting the captain of th ISS, he said he would drop her down a few feet for me :D
 
Dead chuffed I saw it! That thing is fast! Never seen / recognised it before. Photo attempts too over exposed on first pass and was cloudy for second when I'd worked out what I was doing wrong.:-(

Thanks for the inspiration in this thread
 
I'm REALLY struggling. Here's a typical effort from last night. It's barely indistinguishable from a blob.

ISS-2.jpg


Lens: Canon EF 500mm f/4 L IS USM plus EF 2x Extender III
Camera: Canon 40D
Settings: 1000mm, 1/1000th at f/8, ISO 800
Technique: Tripod, MN393 head, manual focus, 6 fps continuous shooting

I must be doing something wrong, and I think it must be the technique. Any suggestions?
 
StewartR said:
I must be doing something wrong, and I think it must be the technique. Any suggestions?
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From my extremely limited but moderately successful attempt - try not cropping so tight that it pixellates that much. If I crop mine that tight it doesn't look much different to yours so zoom out a bit and then give it some fairly aggressive sharpening. You might be surprised at what you have.
 
That's pretty much what I got with my bridge Stewart. Most of it I can put down to a combination of it not managing to focus sharply (and being less than razor sharp wide open @ 720mm!) and my overhead panning. Not sure if there's another pass tonight, if so, I'll try with my D800 and 70-300 while leaving a film body and wide angle to catch a streaker!
 
StewartR said:
I'm REALLY struggling. Here's a typical effort from last night. It's barely indistinguishable from a blob.

I must be doing something wrong, and I think it must be the technique. Any suggestions?
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Hi Stewart

I knew I had seen a picture on here taken with stacked convertors.

HERE

I guess you have all the kit to hand :D

David
 
Willid1 said:
I knew I had seen a picture on here taken with stacked convertors.

HERE

I guess you have all the kit to hand :D
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Wow. Thanks David.

Yes I do have the kit (I've done garden birds at f=2000mm actual before, just for fun), but I think the problem must be my technique.

I think I need to work on smooth panning. Looking at my sequence of shots form last night, the ISS jumps around quite a lot from one frame to another. That doesn't feel right. Plus, I'm concerned that I haven't got the focus spot on. I tried to focus manually on a bright star, but I didn't find it easy and I could have been a tiny little bit out...

Try again tonight, hopefully...
 
StewartR said:
Wow. Thanks David.

Yes I do have the kit (I've done garden birds at f=2000mm actual before, just for fun), but I think the problem must be my technique.

I think I need to work on smooth panning. Looking at my sequence of shots form last night, the ISS jumps around quite a lot from one frame to another. That doesn't feel right. Plus, I'm concerned that I haven't got the focus spot on. I tried to focus manually on a bright star, but I didn't find it easy and I could have been a tiny little bit out...

Try again tonight, hopefully...
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If you can get the tripod roughly aligned you could lock off/add lots of friction to the pan axis on the head (I assume you can on the manfrotto head) should help a bit. I'll be trying this evening if the clouds play ball.
 
Just had a go and got a result marginally worse than the results StewertR managed. Is it just focus?

Settings where 1/1000 f6.3 ISO 4000. I tried 1/2000 f8 ISO 800 and couldn't see even a spec so had to quickly adjust, did I go too far maybe?

edit: I think I must have knocked the focus. As the moon shot I took initially wasn't as sharp as I think it should have been.
 
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I got a few will upload tomorrow.... Can't really make it out in mine but defiantly tell its not a star. I'm well pleased for a first attempt and at only 400mm!!
 
StewartR said:
Plus, I'm concerned that I haven't got the focus spot on. I tried to focus manually on a bright star, but I didn't find it easy and I could have been a tiny little bit out...

Try again tonight, hopefully...
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This may be your focus problem;) The nearest star to earth is 4.2 light years away (10^13km). The ISS is in orbit around the earth so nearer than the moon which is only 385,000km. Your focus could be out by a factor of light years :thinking:

I haven't tried it (but will for a laugh), but maybe DOF master can help:)
 
OK think I've got focussing sorted. The ISS is 370km from the Earth. That's damn close compared to the Moon and other celestial bodies.

If you bung a camera with a 1.6x crop and a focal length of 1000m at f8 into DOF master you get a hyperfocal distance of 6464m.

HTH ;)
 
RJL2005 said:
OK think I've got focussing sorted. The ISS is 370km from the Earth. That's damn close compared to the Moon and other celestial bodies.

If you bung a camera with a 1.6x crop and a focal length of 1000m at f8 into DOF master you get a hyperfocal distance of 6464m.

HTH ;)
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Thanks. I'd already done that myself, as it happens. I knew I had to pre-focus, and from my back garden I had the choice of objects several hundred metres away or several light years away; DOFMaster told me that the latter would be correct.

I think my problem might have been that I simply didn't focus on the star very accurately. Next time I'll try to get the star centred in the frame, lock down the tripod head (assuming I can do that without moving it), and focus using 10x live view. Does that sound like a good idea?
 
It'd be a damned sight faster to focus on the moon, if it's about! :)
 
stewart - you've got a sigmonster in stock haven't you ? - try that with a converter :LOL:
 
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