imaging question

I see shots like this that claim to be made at 400mm http://www.flickr.com …195483914/in/ph​otostream/. When I shoot orion and andromeda with a 300mm they are about the size of a quarter on my frame. Are images like the one above actually filling the entire frame or are they massively cropped? I have seen images taken with wide field refractors similar to this as well, and they are usually 200-600mm. I am a bit confused by all of this but the only conclusion I can draw is that you gain a tremendous amount of detail by stacking these long exposures which allows the image to then be zoomed and cropped. Can anyone fill me in on whats happening here?

calypsob wrote in post #15372359
the only conclusion I can draw is that you gain a tremendous amount of detail by stacking these long exposures which allows the image to then be zoomed and cropped. Can anyone fill me in on whats happening here?

Objects like the Andromeda Galaxy extend a lot further than you might think. But it really does need a long exposure to capture the full extent. I reckon the image you linked to must be very close to being a frame-filler.

This is a single framing shot with a 300mm lens on a 40D. Jpeg straight from the camera with no processing or cropping. Just resized.
You can see the dust lanes in this shot (2 min) and the one you linked to (1hr). As Frank said, more exposure = more galaxy.

I would also have to assume he is using some type of tracking mount. I am very new to AP and cant see how you get a single shot over 30 sec with out some star trails

Hello, I stumbled upon this thread, and thought I'd weigh in. You are correct in that stacking long exposures results in more detail, but only if you are able to get to the threshold of exposure for those details. you could stack a million 5 second exposures of andromeda, and you'd get a buttery smooth shot, but not the extra nebula clouds that you'd get from one 1 minute exposure, or one 2 minute exposure. Stacking adds and averages the information, so it helps reduce grain, and intensifies things that appear only faint in one exposure. I'm fairly new to this too, and there's a steep learning curve. Lots of image processing stuff still escapes me. I shot that with the canon 400mm 5.6. The image in the link is indeed cropped, but not in an overly meaningful way. Here is one frame from the stack. Not filling the frame completely, but not too far off from the final. Hope this helps. http://www.flickr.com …8293407156/in/p​hotostream

thanks everyone, my curiosity is appeased. I keep putting off the purchase of a CG5gt or an ioptron smarteq pro because of my budget and my knowledge of the necessary equipment to get the shots I want. Regulus thanks for sharing the image, that helps put things into perspective. I think I may be happy if I just get a good eq mount for now and use my 300mm telephoto, then I can pick up a refractor later on next year. At least then I can do some good exposures, it would be terribly depressing to have a mount without a lens capable of getting decent shots or a good refractor without a decent mount.