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Old 22-02-2021, 05:13 AM
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Don Pensack
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Join Date: Aug 2006
Location: Los Angeles
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Quote:
Originally Posted by gregbradley View Post
Hey Don,

What's your view on native short focal length eyepieces versus Barlowing a longer focal length with a good Barlow/Powermate?

Do the look the same or do they lose a bit? I mean in general as I am sure there are lots of possible scenarios, and not all eyepieces would behave the same, but in general what would you expect?

I am thinking most likely there would be a gain going native as there would be less glass but then some eyepieces gain better correction by using a Barlow/Powermate.

Greg.
If it's a high-end Barlow, like a Baader VIP or TeleVue powerMate, there is no difference in performance between the higher power eyepiece and the Barlowed lower power eyepiece in general.
Except:
--the higher power eyepiece without a Barlow will be a lot lighter and put less stress on the focuser.
--the lower power eyepiece with a Barlow may, in some circumstances, show more light scatter or internal reflection. That depends a lot on the Barlow.
--the combination of Barlow and Eyepiece might be difficult for users of coma correctors. That stack can get very long and heavy.
--a lower power eyepiece that has induced astigmatism from fielding a short fat light cone might have less astigmatism when used in a Barlow.

I would also comment that my lifetime-best view of Jupiter was with a PowerMate (4 elements) + Paracorr (5 elements) + 8mm Ethos (9 elements). It looked like a Christopher Go or Damian Peach image, only sharper. Full technicolor, too. No more light scatter than I saw in the eyepiece by itself. Different colors on each moon, and albedo features on Ganymede. The keys: great optics and stunningly perfect seeing. Lens count? Not very important, it seems, at least with optics of that quality.
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