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Identifying eyepiece aberrations

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#26 photiost

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Posted 16 October 2013 - 01:06 PM

Well done !! :cool:

#27 stevereecy

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Posted 28 November 2013 - 03:29 AM

Hi, Hope you can help. I just bought a used nagler. I tried it in two telescopes, both colimated, and had the same effect. Both scopes were reflects and had equilibrated their temps. When I looked at the Orion nebula, the gas cloud looked great, but all the bright stars like the trapezium looked mushy...I couldn't get them to snap into focus. Thinking that it might be the seeing conditions (doubtful because the sky looked good and wasn't twinkling), I turned to look at a distant light tower and I was still having trouble getting focus. Lastly, when I scanned the stars in general, I was seeing what sort of looked like the effect you might get if you were trying to look through crinkled celephane. This was very, very, VERY, subtle, but I could see it. Any first guesses regarding the problem?

Thanks in advance

Steve

#28 ibase

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Posted 28 November 2013 - 08:43 AM

Hi,

Also have some Naglers (bought used too) and they are sharp & work very well, depending on the scopes being used.

Posted Image
L-R: Naglers 9mm (T1), 12mm (T2), 5mm (T6)

The Nagler 5mm does not provide sharp-focus with my 8" SCT/f10 because it yields too much power (400x); it's more suitable for other scopes in the stall like the refractors (2.5", 3", 4", 6").

What focal length is your Nagler? Have you used it on any other scopes (like refractors)? Thanks.

Best,

#29 stevereecy

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Posted 28 November 2013 - 12:32 PM

The Nagler is a 9mm, and both scopes are 5mm.

#30 ibase

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Posted 28 November 2013 - 01:09 PM

The Nagler 9mm should focus fine on your 10" Dob, and so with the Cometron refractor. Having eliminated other possible sources of the problem (collimation, cool-down, seeing) the eyepiece could be at fault, perhaps you should arrange for a return/refund.

Best,

#31 mnpd

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Posted 20 December 2013 - 02:19 PM

Outstanding post! And, I thought I knew something of eyepieces. This one is printed out and stays near the top of my reference literature.






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