telescope magnification

opticsplanet.com · Posted: Mon Oct 04, 2004 8:17 am Post subject: Voyageur magnification

Hi Paul

If you are using the 4mm with a Barlow lens you are at a very high magnification, or nearly 500x. In a telescope as small as one of the NorthStars, a fuzzy image at such a high magnification is normal. Even in a very large and expensive telescope, it is rare to get a sharp image at such high magnification.

My advice for all observing, no matter what the telescope, is to use only as much magnification as needed to view an object satisfactorily. In a telescope like a Northstar you will have your best viewing at magnifications of from 50x to perhaps as high as 140x on nights where the atmosphere provides good seeing conditions. Using more magnification than this will result in fuzzy images in your Northstar.

If your Barlow is bad, you should notice a problem using it with all eyepieces. Still, if you would like to return just the barlow for a replacement and try another one, I would be glad to help. Let me know and I will try to find one for you.

If you have any more questions, don't hesitate to contact me.
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Mark · Guest

Given Focal Length of 900m and width of 4 1/2 inches. The maximum usable magnification if about 50 times with Width, i.e. 4.5 x 50x = 225x. But realistically you should expect less.

If you use the 20mm with the 3x barrows, then you'll be at 135x. Otherwise your 4mm will give you 225x.