I have a reflector telescope with a 114mm aperture and 1000mm focal length. I find that to get the clearest image I can use a 4mm eyepiece, or with my 5x barlow a 20mm however, seeing that I am very interested in astro photography when I try to photograph Jupiter for instance, through the telescope eyepiece, being the size of about a green pea seen through the scope, there is not enough pixel data for my canon eos t2i rebel dlsr to capture a clear photo. Is there some way to enlarge the photo for the camera without blurring the planet's details from over magnification?


1 Answer 1


If you were using both a camera lens and an eyepiece (afocal method), try eyepiece projection. In this method, the eyepiece is the only optical element between the prime focus and the detector. You would need an eyepiece projection adapter tube to connect the camera body to the telescope's focuser. A longer tube will increase magnification but also increase exposure time. Any tube length which reasonably balances those concerns should be OK.

It's also possible to use a Barlow lens and no eyepiece to extend the effective focal length of the telescope. If your adapter tube is wide enough to accommodate the Barlow, you may be able to use it this way too.

Astronomy Source has an article with more details about eyepiece projection. Tele Vue has an overview of that and other methods, plugging their own products of course.

  • $\begingroup$ I have used the camera with its lens and without. I have different diy tube lengths to accommodate various eyepieces. Though the explination was a bit confusing I am under the belief that eyepiece projection requires that a 2" gap is left between the eyepiece and front of the camera. Is that 2" gap a fixed value or does it use a formula to accommodate the telescope' s focal length? I'm sorry I struggled to understand the formulas in the article? Also when I googled the method further some say using a barlow is better, how would this technique differ as well be implemented? Thanks for helpi $\endgroup$
    – Bre
    May 2, 2018 at 23:27
  • $\begingroup$ @Bre I have expanded this answer. $\endgroup$
    – Mike G
    May 9, 2018 at 18:51

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