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lx80 sct 10" maximum magnification


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#1 dotz59

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Posted 25 May 2013 - 06:30 PM

does anyone out there know the maximum magnification on the lx80 SCT 10" ?
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#2 MistrBadgr

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Posted 25 May 2013 - 07:22 PM

Well, if you were on a mountain top with perfect weather, you could probably take that scope to 600X or 60X per inch.

At sea level, with those same perfect conditions, the limit might be 40X per inch or 400X.

Most long time observers I know rarely go over 300X, unless it is for something special and probably on the Moon. Beyond about 300X, atmospheric disturbances can limit the effectiveness of the extra magnification.

To put in in a different way, you can consider the size of the image going through the pupil of your eye. Yours scope has a diameter of about 250 mm. At 250X, the image is 1 mm across. At 500X, the image is 0.5 mm across. Not even considering the limits of the scope, the various imperfections in your eye start to have an effect.

Depending on whose information you read or listen to, the optimum image size for information gathering is somewhere between 1 and 2 mm as it goes through your eye lens. Going in either direction from that figure, the contrast decreases.

Going to higher magnification from the optimum, the imperfections seem to magnify faster than the information you are trying to see and the fuzz just compounds. Also, since you are spreading out the amount of light in the area of the image as you go higher and higher in magnification, the image gets dimmer and dimmer.

Going farther and farther from optimum in the low magnification direction, gives you a wider field of view to see larger and larger objects, but more and more your your eye lens gets involved. Eventually, you reach the edge of your pupil and part of the image is lost. With your scope, the center of the image will look darker than around the rim. If you have any imperfections in the outer part of your eye lens, they will start showing up as spikes on stars.

As a mater of fact type practical limit for your scope, somewhere around the equivalent of a 5 or 6 mm eyepiece is a reasonable top end magnification limit for ideal circumstances.

On the low end, if you are young and your pupils are opening up to around 7 mm, the lower magnification limit would be about 36X. That would require a 70 mm eyepiece, which is not made as far as I know. In order to get that low, you would need a focal reducer. For me, with a light polluted back yard and an older eye, I need to limit the image size to 5 mm or even 4.5. At 5 mm, the minimum magnification to make your scope work for my eyes would be about 50X. This would require a 50 mm eyepiece, which is also not made. I would have to use a focal reducer on the scope.

Hope this helps,

Bill Steen
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Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma




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