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Perfect Focal Length For Solar System Objects


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Hi all, I have a celestron 120mm refractor with a focal length of 1000mm, I am thinking of getting a barlow for close ups of the moon and planets, with my focal length is there an optimum barlow to use such as x2, x2.5, x3 or x5. I'm new to imaging so it may seem like a simple question but is there a perfect focal length I should be looking to work at for the moon and especially the planets.

Thanks very much and clear skies to you...

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Generally the "best" is the same as the f number, so in your case an 8mm eyepiece.

Various opinions around concerning the maximum but I would say that if you went to a 6mm eyepiece then thay would be close to the maximum usable magnification for the vast majority of conditions. Once is a year a 5 mm may be usable but not often.

Add in that as the scope is 120mm and f/8 I assume that it is not an ED refractor so chromatic aberation will come into effect at high magnification.

As a barlow is simply a magnifier for an eyepiece cannot answer about that.

And all of this depends on the quality of whatever you buy.

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Hi Mamsoth thanks for asking this question I was wondering the same. Using Caprison guide I have a SW 150P 150 x 1200 = F8 so an 8mm eyepiece would about right for me as well.

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