Though I must admit I'm a little suspect of his claims. A nikon DSLR attached to that scope would only give a magnification of around 40X. I'd like to see the original image uncropped to judge the field of view.
According to my calculations (assuming the nikon has a similar chip size to the canon) the field of view should be 38.5 X 58.5 arc min with a resolution of 1.14 arcsec/pixel. If the IIS is 80 m long and orbits at an average of 350 Km then its angular size in arcsecs as viewed from earth is only 47 arcsec. This means in his original image the ISS would have only been 41 pixels long. A standard high res Canon image is 3072 X 2048 pixels. With an uncropped image and the knowing the objects size and distance from us then the imaged resolution can be worked out and finally the telescope f/ratio and focal length.
If you can get the full imaging details I'd love to know how he did it.
I seem to remember getting the ISS in binos one night and being able to make out some shape at 8x so at 40x it may be possible to capture the detail shown.
Ok here are a couple of images taken with longer FL instruments with much higher magnification, greater aperture to provide better resolution and multiple image stacking to improve signal to noise.
To get his shot with a single image with a DSLR through a 80mm scope operating at f/16 (wonder how he did that and still work at prime focus, negative projection using a barlow or teleconverter I guess, or positive eyepiece projection) Everything must have come off just perfect at that moment.
Don't get me wrong. I'm not saying that the image isn't as Asi says it is, but I am a tad scepticle, principally due to the resolution he has achieved with the given aperture of the scope and would really like to know how it was done.
Last edited by [1ponders]; 31-03-2006 at 01:28 PM.
I'm only quoting what the guy told me, but I left out where he used a 1.4X 'converter' ?? to get his F16 & 1/25th exposures....about a dozen stacked in registax...& now you know just as much as I do lol.
I've just been doing a bit more digging for comparison images and resolution obtainable with an 80mm scope and came across a few Peter K has on his K3CCDTools website of sunspots taken with an 80mm refractor at various focal lengths. A couple of the closeup ones are taken at f/14+ so it is possible to compare them with this one which covers a similar field of view and includes the IIS
Man what a difference good seeing makes. That is fantastic focusing as well. I'm willing to heat humble pie That ISS image is only half what I calculated at about 25 pixels in this compressed image. Fantastic processing in the enlargement.
All hail ASI's ISS imager. and as for the Ponders school of astrophysics, are you really a mad scientist that teaches horticultural stuff to cover your real identity!
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That ISS image is only half what I calculated at about 25 pixels in this compressed image. Fantastic processing in the enlargement.
And yes I do teach hort stuff. Gotta pay for this hobby somehow.
