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Old 08-05-2011, 01:14 AM
ausastronomer (John Bambury)
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Join Date: Mar 2005
Location: Shoalhaven Heads, NSW
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Quote:
Originally Posted by bobson View Post
I have 17mm Nagler and can say its great eyepiece in my Bintel 12" Dob! It Barlows very well and give me great views of the Moon and planets as well. I even prefer it over my 10 mm Pentax XW when Barlowed for planets.

cheers
Hi Bob,

I am somewhat confused as to how you could perceive this.

I own both of those eyepieces (10mm Pentax XW and 17mm Nagler T4), have done for many years; and have used both of them in many different telescopes. They are individually both excellent eyepieces. The 17mm Nagler excels as a low/medium power "ultra" widefield for DSO's. The 10mm Pentax XW excels as a medium/high power widefield for both DSO's and Lunar/Planetary targets. In terms of the important criteria for lunar/planetary performance IMO the 17mm Nagler T4 falls well short of the 10mm Pentax XW. Namely, light throughput, on axis sharpness, neutral colour fidelity and contrast. The only reason I can think of as to why you prefer the 17mm Nagler T4 barlowed over the 10mm Pentax XW as a lunar/planetary eyepiece, is that it gives noticeably higher magnification than the 10mm Pentax XW. What barlow are you barlowing the 17mm Nagler in?

FWIW also, the 17mm Nagler T4 is a 2" only eyepiece and not suitable for use in his TV 2.5X powermate, so whatever he buys he should stick with a 1.25" barrel IMO so he can at least use the eyepiece in his barlow and get double duty from it.

Cheers,
John B
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