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Originally Posted by iceman
Very nice Erwin, it's almost the exact same CM as my shot from the other day.
I love the image scale, great shot! |
Hi Mike,
What amazes me about your first shot is the used focal ratio of f/15 and still get a great amount of detail. Most top imagers use anything between f/30 and f/55, although I've found that anything between f/30 and f/35 works best, depending on the seeing.
Off-axis projection means putting the camera not straight behind the eyepiece but a bit off-centre. With a simple eyepiece design like a Kellner this method introduces colour abberation, which can be used to compensate for atmospheric dispersion (the lower the altitude of an object the more different the blue light will be bent by the atmosphere than the red light, causing colour fringing). Used correctly it compensates almost entirely the dispersion, resulting in higher contrast images with less artefacts.
Cheers,
Erwin