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Hi all
When I want to work out the maximum magnification for any given telecope, I use the following basic forumla. It works like this, the maximum magnification per inch of objective is around 50x. Therfore a 3" telescope has a maximum magnification of 150x, a 10" would have a maximum magnification of 500x. This formula will work with any given apature.
Of course due to factors, such as weather condition, these maximum magnifcation may not be obtainable.
A beginner would start out with say an 8" reflector with an f/ratio of about f6. The maximum magnification would be around 400X. So we need to look at an eyepiece/barlow combination that would give use the best range of magnifications. Usually these scope will be supplied with a 25mm and 10mm eyepiece, giving a magnification of 48x and 120x. If a good quality 2x barlow is include we the get the following magnification 48x, 96x,120x and 240x.
As you see by just including a 2x Barlow we have gained a good range of lower, medium and high magnifications. The maximum magnification is 240x well short of the 400x but remember due to factors, such as weather condition, it may not be obtainable.
When it comes to imaging the magnification of the telescope with the camera mounted directly to it (prime focus) can be determined by dividing the focal length of the telescope by 50. For example, a 1,000mm focal length telescope would yield 20 x magnification compared to a normal 50mm camera lens.
When imaging the planets most people use negative projection e.g. teleacope+barlow+camera. With the setup I used to image Mars the magifiction would be around 250x e.g. 10" f10 has a focal lenght of 2500mm mulitply that by 5 (5x Powermate), we end up with a focal lenght of 12500mm. Divide this by 50 and we end up with a magnification of 250x. In terms of image scale we end up with about 0.12 arcsec per pixel.
Anthony
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