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Equipment Discussions >> Eyepieces

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ibase
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Reged: 03/20/08

Loc: Manila, Philippines 121*E 14*N
Re: Identifying eyepiece aberrations new [Re: Starman1]
      #5964933 - 07/10/13 11:02 PM

Quote:

Quote:

Great post! (Where is #15? Don't want to miss out on anything )

Best,



I incorporated #15 into another point, but forgot to renumber #16.
My original notes had over 40 different points, but I became aware, after reading them, that most could only be identified in a lab, so I restricted the points to the ones most germane to field evaluation.

One thing I didn't mention was how an over-corrected eyepiece might cancel some under correction from a primary to result in an absence of spherical aberration in the final image. When eyepieces were made by hand to match the scopes made (in the 18th century, for example), I wonder if eyepieces were ever refigured to do just that.




Thanks Don; that facet of the possibility of an EP canceling spherical abberation in the scope's primary is very interesting and may help explain why some observers might feel strongly for or against certain EP's - it depends on the scopes that the EP is being used on to either give good or not-so-good views.

Best,


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ausastronomerModerator
Carpal Tunnel
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Reged: 06/30/03

Loc: Kiama NSW (Australia)
Re: Identifying eyepiece aberrations new [Re: ibase]
      #5965212 - 07/11/13 05:53 AM

I have made this a sticky thread. When the thread dies down I will move it to "best of eyepieces thread"

Cheers


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Kraus
Pooh-Bah


Reged: 03/10/12

Loc: Georgia.
Re: Identifying eyepiece aberrations new [Re: ausastronomer]
      #5979958 - 07/19/13 02:49 PM


Naglers have no aberrations.

Kraus recommends Naglers.


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JustaBoy
Post Laureate
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Reged: 06/19/12

Re: Identifying eyepiece aberrations new [Re: Kraus]
      #5979973 - 07/19/13 02:57 PM

Did you drink Kool-Aid for breakfast, Kraus?

Edited by JustaBoy (07/19/13 02:59 PM)


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cuir
Carpal Tunnel


Reged: 03/03/07

Loc: Up north.
Re: Identifying eyepiece aberrations new [Re: JustaBoy]
      #5981248 - 07/20/13 11:25 AM

Saved on both PC and phone in a slightly modified version. (saved as HTML document with white fonts and black background).

Your post is joining a growing library of credible and notable text documents that can be good to have on hand in the field, specially at public events. It joins notable texts such as David Knisely's "Filter Performance Comparisons For Some Common Nebulae", a copy of The Delaware Valley Amateur Astronomers's Eyepiece Parameter Calculations, the Saguaro astronomy club's Best objects in the new general catalog By A.J. Crayon and Steve Coe, my spreadsheets and a few other texts of this nature.

It may be small an honor, but still, your post is joining my "best documents" shortlist. Thank you for the good work.


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photiost
scholastic sledgehammer
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Reged: 12/14/06

Loc: Montreal, Canada
Re: Identifying eyepiece aberrations new [Re: cuir]
      #6141000 - 10/16/13 02:06 PM

Well done !!

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stevereecy
super member


Reged: 09/15/05

Loc: North Florida
Re: Identifying eyepiece aberrations new [Re: ibase]
      #6220715 - 11/28/13 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


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ibase
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Reged: 03/20/08

Loc: Manila, Philippines 121*E 14*N
Re: Identifying eyepiece aberrations new [Re: stevereecy]
      #6220891 - 11/28/13 08:43 AM

Hi,

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


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,


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stevereecy
super member


Reged: 09/15/05

Loc: North Florida
Re: Identifying eyepiece aberrations new [Re: ibase]
      #6221344 - 11/28/13 12:32 PM

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

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ibase
Vendor Affiliate
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Reged: 03/20/08

Loc: Manila, Philippines 121*E 14*N
Re: Identifying eyepiece aberrations new [Re: stevereecy]
      #6221440 - 11/28/13 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,


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mnpd
professor emeritus


Reged: 06/28/05

Loc: Nashville, Tennessee
Re: Identifying eyepiece aberrations [Re: ibase]
      #6263844 - 12/20/13 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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