International Space Station w/ DSLR & 400mm Lens

Even 1/200 is way faster than mine showed at 1/6th of a second. How were you able to get that high? And at 500mm, the thing was only a dot, so the metering might not have been correct. By comparison, the ISS was way smaller looking and much dimmer than Jupiter, which it went near. I did get about 15 frames in, most of which were just wiggly lines, but a few were looking like dots. Even magnified to 200% I saw nothing but a dot. So not sure how anyone resolved what shows in that first shot by the OP or the other ones.

Neither time I tried though, was the track of the ISS anywhere near overhead. I might have to wait for a better time.

Keep trying guys! I'll try again when the sky's clear up here in CA...

canonloader wrote in post #8990150
Neither time I tried though, was the track of the ISS anywhere near overhead. I might have to wait for a better time.

Ah, see when I captured it at 1200mm it was nearly directly overhead, and the brightest thing in the sky. Some of my 1/200th shots were overexposed.

On my 450D it was still only perhaps 100 pixels across at that focal length, but clearly the ISS. Couldn't make out the shuttle though. Can't wait to get some good tries with my 2800mm scope, though manual tracking with that is going to be a nightmare...definitely have to use a webcam.

So far, both tracks I have seen were fairly low in the sky, about where Jupiter is in winter, and not nearly as bright as Jupiter. I will keep trying though.

OK. Out comes the calculator.
<tap>...<tap>...<tap>..<carry the one> .. <tap>...<tap>....<mumble>...

Wikipedia says the ISS is 109m x 73m and is at an average altitude of 370km.
That makes it 50 arcsec across if it's directly overhead. If it's 45 degrees above the horizon it will be about 40 arcsec.
For comparison, Jupiter is currently 40 arcsec in diameter and mag -2.4 so whatever setup works for Jupiter will be pretty much spot on for an overhead pass of the ISS. You just have to catch it.

For a 40D (I think your 450D uses a similar sensor), at 1200mm f/l one pixel is one arcsec so the image is about 50 pixels.
For your webcam at 2800mm f/l the image would be about 115 x 160 pixels. That should be entertaining, keeping that within the sensor area.

I hope that's helpful. It hasn't helped me - It's still cloudy.

Steve.

Is that monitor pixels, like 72 to the inch?

Sensor pixels. The ones that a 10MP camera has 10 million(ish) of.

Steve.

SteveInNZ wrote in post #8997073
For your webcam at 2800mm f/l the image would be about 115 x 160 pixels. That should be entertaining

I'm a bit new to the whole space photography/extreme focal length stuff, but can anyone fill me in on how a webcam (usually a pinhole 'lens' design) can be attached to a scope or lens for 2800mm F/L ?

SteveInNZ wrote in post #8997073
For a 40D (I think your 450D uses a similar sensor), at 1200mm f/l one pixel is one arcsec so the image is about 50 pixels.

Just opened the image up in paint and yes, you're almost spot on. The ISS was tilted slightly, but end-to-end it was about 50 pixels, max.

Maybe I won't bother with the webcam then!!

Something that comes to mind is the relative brightness of the ISS would be changing constantly due to the varying angles of it's surfaces/orientation to the sun.

M_ark wrote in post #9000133
I'm a bit new to the whole space photography/extreme focal length stuff, but can anyone fill me in on how a webcam (usually a pinhole 'lens' design) can be attached to a scope or lens for 2800mm F/L ?

The 2800mm f/l is the focal length of the telescope (lens). The focal length stays the same regardless of what is attached to it.

The lens in a webcam isn't a pinhole lens in the classical meaning of a pinhole lens (ie. where a small hole shows lens like properties). It has a real lens that is small and includes a relatively small aperture to get a good depth of field.

For astronomical use, the standard lens is removed and the remaining part is put on the back of the telescope in just the same way that a DSLR might be. But it has a few advantages over the DSLR for some applications - planets (and maybe space stations).

If you imagine taking a picture of Jupiter with a DSLR. The frame is roughly 4000 x 3600 pixels but Jupiter is only 70 pixels in diameter. The rest of the frame is just black. That's a lot of sensor area that's doing nothing so why put it there. The webcam pixels are about the same size but the overall sensor size is just the right size to be filled with Jupiter. Because there are less pixels to read out, you can do it much faster and can take 15 or 30 frames per second compared to 1 frame every few seconds with a DSLR. The reason that it takes so long with the DSLR is that you have let any movement die down which is another advantage of the webcam. No moving parts.

By being able to take many frames, you have the ability to use that data to reduce noise, increase the effective bit depth and improve image resolution.

Steve.

Maybe the next clear night, I ought to try Video Mode with the 7D and then try and do a frame grab?

canonloader wrote in post #9003955
Maybe the next clear night, I ought to try Video Mode with the 7D and then try and do a frame grab?

Would love to see some results from 7Ds being used in video mode.

I will give it a try, and also use manual mode to try for some stills. I have tried Av mode and that doesn't work.

Not sure if this will help anyone out but there is a couple of excellent Iphone apps that may be of some assistance to you.

1. ISS Visability, this will give you details of ISS passes in your area including times, duration, altitude and then you can show the path on either sky charts or ground plots. You can search for all passes in your location for between 10 & 30 days and then choose the ones with the better durations etc.

2. Pocket Universe, again this uses your current location and will tell you everything from sunrise/set times to which other planets are visable and what times you can see them. A very useful tool is the ability to actually show the night sky which changes as you rotate, helpful for finding polaris and it also includes details of meteor showers including peaks and moon phases etc.

Like I say not sure if it is interesting to you guys as you are so clued up on these things but to someone like me that wouldn't know jupiter from pluto when looking in the sky it has given me some really useful information.