Hi
Just re-entering some text that was deleted some how during upload
When we are talking about the maximum magnification for any given telescope the general rule is 40x to 50x per inch of apature. Therefore a the maximum magnification for a 10" scope will be between 400x to 500x. But in practice as you will know these high magnification are unobtainable, due to may factors such as weather etc.
In my experience when observing planets visual I offend use medium magnification (about 200 -250X), I end up with a smaller, sharper image with out the blurring effect cause by excessive magnification.
I have spent some years now doing planetary image and like may have been on a steep learning curve. What I have found is that there are may factor that effect the final produce e.g. the weather (something that we can not control), collimation, temperature, focal length, Image Scale, focus, frame rate, gain, processing etc.
For planetary imaging, Image scale is an important factor, since you will taking pictures of small targets (Mars, Jupiter, Saturn, etc.) you will need to magnify these objects in order to capture sufficient detail. For imaging, magnification is a function of focal length and the focal length will determines image scale.
So the first thing that must be considered is what amount of magnification should be used when imaging the planets? Ideally, an image scale of about 0.25 arcseconds/pixel is recommended. This should reveal the most detail possible under good seeing conditions without being magnified too much. The required focal length depends on the size of the pixels in your CCD camera. For a typical webcam with a pixel size of 5.6 microns you are looking at a focal length of 4600mm to achieve an image scale of 0.25"/pixel.
If you wish to work out the magnification of your imaging set up us this formula;
Focal length of telescope / 50 = Magnification.
Example 1 – Prime focus
A Canon EOS 350D plus an ED80 will work out to a magnification of 12x
600/50=12
Example 2 – Negative projection (Barlow)
A 5x Powermate plus 10” f10 SCT will work out to a magnification of 250x
2500x5=12500 12500/50=250
As mention above, an ideal image scale of 0.25 arcseconds/pixel is recommended, but in the real world of planetary imaging the image scale can be a lot smaller and as image scale is determined by the focal length, the focal length is going to be larger. Therefore the typical focal length when imaging with a webcam can range between f20 to f45. However, longer or shorter focal lengths can be used with excellent results depending primarily on the atmospheric conditions.
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For further reading I strongly recommend that you read Damain Peach article on "An Examination of optical issues on real Planetary Images" at http://www.damianpeach.com/simulation.htm</o:p></FONT></P>