I want to see Jupiter with moon. So am planning to build telescope. Can I use 75mm Plano convex lens with 1000mm focal length?

  • $\begingroup$ See uhoh's excellent answer to a similar question yesterday. astronomy.stackexchange.com/a/47954/2365 You can build a telescope... but with small cheap lenses you won't see much. We know the lenses are small. Are they achromatic? Most amateurs use mirrors rather than lenses. Better results for less money. $\endgroup$
    – James K
    Commented Dec 28, 2021 at 15:38
  • $\begingroup$ @JamesK this lens is f/12.5, that one is f/2, so totally different question with opposite answers. ("5 cm diameter convex lens with 10cm focal length"). Not a duplicate at all. $\endgroup$
    – uhoh
    Commented Dec 28, 2021 at 22:36

1 Answer 1


Can I use 75mm Plano convex lens with 1000mm focal length

tl;dr: Go for it!

First see this answer to Will these simple 2 convex lens arrangement telescope see the moon clearly? but your question is quite different, not a duplicate and I think you can have some success!

You will have some chromatic aberration but at f/12.5 it won't be so strong, and you certainly won't have a problem with spherical aberration.


In fact it's probably time that get answered so I've added a bounty, and if nobody answers it after that then I will!

Yes, please carry out your experiment! With a 75mm plano convex lens with a 1000 mm focal length, you will have a low quality image due to chromatic aberration but with a good eyepiece and stable way to hold it at the objective lens' focal plane (that's not easy!) you will be able to catch a glimpse of Jupiter's Galilean moons and probably see some bands of clouds.

They will not be clear, the image won't be stunning, but it will be very exciting to DIY yourself all the way to Jupiter for a few moments!

Go for it!


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