Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Identifying eyepiece aberrations

  • Please log in to reply
34 replies to this topic

#26 photiost

photiost

    Surveyor 1

  • *****
  • Posts: 1967
  • Joined: 14 Dec 2006
  • Loc: Montreal, Canada

Posted 16 October 2013 - 01:06 PM

Well done !! :cool:

#27 stevereecy

stevereecy

    Vostok 1

  • -----
  • Posts: 104
  • Joined: 15 Sep 2005
  • Loc: North Florida

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

ibase

    Aurora

  • *****
  • Posts: 4802
  • Joined: 20 Mar 2008
  • Loc: Manila, Philippines 121°E 14°N

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

stevereecy

    Vostok 1

  • -----
  • Posts: 104
  • Joined: 15 Sep 2005
  • Loc: North Florida

Posted 28 November 2013 - 12:32 PM

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

#30 ibase

ibase

    Aurora

  • *****
  • Posts: 4802
  • Joined: 20 Mar 2008
  • Loc: Manila, Philippines 121°E 14°N

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

mnpd

    Viking 1

  • -----
  • Posts: 676
  • Joined: 28 Jun 2005
  • Loc: Nashville, Tennessee

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.

#32 tommm

tommm

    Sputnik

  • -----
  • Posts: 40
  • Joined: 16 Dec 2015

Posted 02 January 2016 - 03:11 PM

May have missed it, but I didn't see reference to the article below.  Thought this would be a good place to put it.

 

http://www.brayebroo...WIDER_AFOV.html



#33 Starman1

Starman1

    Vendor (EyepiecesEtc.com)

  • *****
  • Vendors
  • topic starter
  • Posts: 28373
  • Joined: 23 Jun 2003
  • Loc: Los Angeles

Posted 02 January 2016 - 03:42 PM

May have missed it, but I didn't see reference to the article below.  Thought this would be a good place to put it.

 

http://www.brayebroo...WIDER_AFOV.html

A lot of controversial claims in that article.  It's interesting to read, but he casually ignores a lot of aberrations in his "favorite" eyepieces, and he makes a number of claims that are unsupported in lab tests, such as increased light scatter from multi-coatings.

Take the article with a grain of salt, even though there is much interesting in the article.



#34 Sarkikos

Sarkikos

    ISS

  • *****
  • Posts: 22178
  • Joined: 18 Dec 2007
  • Loc: Per sylvam ad astra

Posted 23 January 2016 - 12:20 PM

Maybe include EOFB (Edge of Field Brightening) as an eyepiece aberration?

 

Mike



#35 Starman1

Starman1

    Vendor (EyepiecesEtc.com)

  • *****
  • Vendors
  • topic starter
  • Posts: 28373
  • Joined: 23 Jun 2003
  • Loc: Los Angeles

Posted 23 January 2016 - 12:31 PM

Yes, maybe as a subset of #13 Light Scatter.

It obviously is a light scatter phenomenon, but what it's from is still conjecture.


  • Sarkikos likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.







Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics