Lens combination for Jupiter

Hi everyone,

I have been using my 12 incg go to dobsenian. Unfortunately, i am not able to get sharper images while watching jupiter, when i am using a combination of 2x barlow ans 0.10 mm lens.

Please guide.

Srikanth V

Hi @vittala.srikanth, does this problem persist with other eyepieces? Or is the image for this particular combination of eyepieces not getting focussed even with the focusser?


Combination 1 - Used 2X barlow and 0.25 mm. Image is ok. But not to my satisfaction. Its ok but not sharp.

Combination 2 - Used 2X barlow and 0.10 mm. Image is too blurry. I tried adjuating the focusser.

I have a 12 inch dobsenian and given the size, i thought the image will be sharper.

Hello @vittala.srikanth,

I’m hoping you may have already considered these, but these some common pitfalls so, I’ll suggest anyway especially because you mentioned you were having a problem with the 25mm eyepiece as well.

  1. Unfortunately the bigger the scope it takes longer to sync with the outside temperature. So, allow the scope to cool / warm further.
  2. Remove the Barlow and check if you still have the problem.
  3. Check with the same Barlow+eyepiece combinations in another scope (hope you find someone who has a similar or a larger scope)
  4. Check with and without the fan being on (some of my mates who have better eyesight than me have always complained about fans being on whilst observing.
  5. Ensure the scope is stood solid and stable if you’ve modified it to have more than three anchor points.
  6. Collimate it again with a star. Remember bigger the scope and bigger the magnification, bigger the errors are too.

All the best, let us know how you got on.

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Also, poor seeing (atmospheric turbulence) makes the image blurry even with perfect focus. This is amplified with higher magnifications. As @Gnana has already stated, using the eyepieces without the barlow should give a better image.

Clear skies,