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

Black outs or kidney bean problems

This topic has been archived. This means that you cannot reply to this topic.
13 replies to this topic

#1 DPT

DPT

    Vostok 1

  • *****
  • topic starter
  • Posts: 101
  • Joined: 18 Oct 2006

Posted 19 August 2015 - 10:19 PM

I was reading through some of the old forums and saw several mentions of black outs and kidney beaning occurring in the 31 mm Nagler T5.  Is this a common occurrence with this particular eyepiece?  Also, how are the newer Televue Delos and the still newer Delite eyepieces with regard to black outs?  I would hate to invest serious dollars only to find out later about serious black outs and having bought eye pieces that are super sensitive with eye positioning to avoid black outs.  I would prefer to enjoy the viewing experience and not get aggravated with finding the "right" location to get the view right. Thanks.



#2 areyoukiddingme

areyoukiddingme

    Fly Me to the Moon

  • *****
  • Posts: 5,410
  • Joined: 18 Nov 2012

Posted 19 August 2015 - 10:34 PM

I don't find any problem with eye placement in the 31mm Nagler. I only have one Delos, the 14mm, and I find it easier to use than my Pentax XWs, which are widely regarded among the most comfortable eyepieces to use.

 

Having said that, I don't wear glasses, so you may find some problem getting close enough with the Nagler in that situation. The Delos would be fine, however, given the 20mm eye relief and adjustable cup.



#3 rolo

rolo

    Cosmos

  • *****
  • Posts: 9,290
  • Joined: 14 Jan 2007

Posted 19 August 2015 - 11:41 PM

Personally, I've never blacked out from kidney beans...



#4 Lew Zealand

Lew Zealand

    Apollo

  • *****
  • Posts: 1,392
  • Joined: 28 Jun 2004

Posted 20 August 2015 - 12:03 AM

I have 5 Delos from 4.5 to 17mm and have no problems with blackouts viewing the night sky.  They are very comfortable and easy to view through.

 

Daytime is a harder test, especially for long ER, wide AFOV EPs and I find the Delos are still good to look through but they have a bit more of a problem with blackouts.  This is almost certainly due to the fact that I prefer to view through all my EPs with the eyecup all the way down while using my glasses (down to about a 1mm exit pupil).  The Delos have such generous ER that even with glasses on, I hover above the EP which I prefer to do though many people do not.  This makes holding the view steady harder and will exacerbate what is usually a negligible blackout problem.  Additionally, I view sitting down at night almost all the time but rarely sit down during the day, which *really* makes holding the image steady tougher.

 

There are other EPs which are far worse to use during the day (Expanse and clones are completely unusable thanks to blackouts/SAEP) but some which are pretty good (BO/TMBs have little of this).  The Delos are pretty good but not perfect.  Frankly, for daytime use a Plossl is a good choice.



#5 Meadeball

Meadeball

    Soyuz

  • *****
  • Posts: 3,572
  • Joined: 22 Oct 2012

Posted 20 August 2015 - 12:59 AM

I've made other people black out with beans ...


Edited by Meadeball, 20 August 2015 - 01:00 AM.


#6 Eddgie

Eddgie

    ISS

  • *****
  • Posts: 26,637
  • Joined: 01 Feb 2006

Posted 20 August 2015 - 07:36 AM

I was reading through some of the old forums and saw several mentions of black outs and kidney beaning occurring in the 31 mm Nagler T5.  Is this a common occurrence with this particular eyepiece?  Also, how are the newer Televue Delos and the still newer Delite eyepieces with regard to black outs?  I would hate to invest serious dollars only to find out later about serious black outs and having bought eye pieces that are super sensitive with eye positioning to avoid black outs.  I would prefer to enjoy the viewing experience and not get aggravated with finding the "right" location to get the view right. Thanks.

 

I do not find the 31mm Nagler particularly prone to blackouts. 

 

A great many wide field eyepieces will black out if you get to far off of axis, but the 31mm Nagler I thought was less inclined to kidney bean than many others.  I use it all the time with no problem.



#7 StarWolf57

StarWolf57

    Apollo

  • *****
  • Posts: 1,127
  • Joined: 22 Jan 2014

Posted 20 August 2015 - 08:59 AM

I was reading through some of the old forums and saw several mentions of black outs and kidney beaning occurring in the 31 mm Nagler T5.  Is this a common occurrence with this particular eyepiece?  Also, how are the newer Televue Delos and the still newer Delite eyepieces with regard to black outs?  I would hate to invest serious dollars only to find out later about serious black outs and having bought eye pieces that are super sensitive with eye positioning to avoid black outs.  I would prefer to enjoy the viewing experience and not get aggravated with finding the "right" location to get the view right. Thanks.

 

 

I can appreciate the frustration. When I first started up again (after being away from the hobby for 25+ years), I had the same problem with the 31T5. It's getting easier now. My eye placement is becoming more "automatic". Stick with it and I think you'll find the same thing. BTW, I have found the Delos EP's to be very easy to use. XW's have that reputation as well, but I haven't had a chance to try mine yet.



#8 drollere

drollere

    Vanguard

  • *****
  • Posts: 2,328
  • Joined: 02 Feb 2010

Posted 20 August 2015 - 09:59 AM

to the OP: people seem to vary in how much the SAEP (spherical aberration of the exit pupil) or "kidney bean blackout" affects them.

 

for me it is an experience equal to having a bug crawling on my cornea. for others, it's just something they move around as they observe.

 

i returned a TV 40mm panoptic because of the problem, so it's not something limited to naglers. many long focal length eyepieces will produce it, although some are more prone to do it than others, depending on the focal ratio of the objective.

 

i've seen it in my 28mm RKE and in a classic 30mm K├Ânig. however, in those eyepieces you have to shift your whole head away from the optical axis in order to produce the blackout. the supreme annoyance occurs when you only eliminate it by directly looking at the center field with head held rigidly in place, and any deviation of the point of fixation to any other part of the field, or relaxed movement of the head, causes the blackout to spring into view.

 

don't rely on judgments posted here. try eyepieces for yourself, in equipment similar to yours. or buy an eyepiece with promise that a return will be accepted if you dislike it. you can't know your allergy to this defect until you have to live with it.



#9 GeneT

GeneT

    Ely Kid

  • *****
  • Posts: 15,720
  • Joined: 07 Nov 2008

Posted 20 August 2015 - 05:39 PM

Never had problems with black outs or kidney bean with a 31 Nagler, or any of my Delos and Ethos eyepieces. 



#10 Scanning4Comets

Scanning4Comets

    Markus, a.k.a. Scanning4Comets

  • *****
  • Posts: 17,938
  • Joined: 26 Dec 2004

Posted 20 August 2015 - 06:11 PM

Any of the Delos, XW's, etc.......any eyepiece with "long eye relief" will black out when you get too close.

 

The 31mm Nagler will do it too.....if you get too close to the lens.

 

In the cases of the Delos or XW.....you can set the eyecup higher to avoid blackouts. In the case of the 31mm Nagler...you can set the rubber eyecup in the "up" position to avoid blackouts as well. Experienced observers don't need to have their eyecups in the "up" position, because they all know where to set their eyes in relation to the top lens, avoiding blackouts.

 

The Type 4 Naglers are really famous for kidney beaning and blackouts.....same with the older 13mm Nagler.



#11 gnowellsct

gnowellsct

    Hubble

  • *****
  • Posts: 16,981
  • Joined: 24 Jun 2009

Posted 20 August 2015 - 09:01 PM

I was reading through some of the old forums and saw several mentions of black outs and kidney beaning occurring in the 31 mm Nagler T5.  Is this a common occurrence with this particular eyepiece?  Also, how are the newer Televue Delos and the still newer Delite eyepieces with regard to black outs?  I would hate to invest serious dollars only to find out later about serious black outs and having bought eye pieces that are super sensitive with eye positioning to avoid black outs.  I would prefer to enjoy the viewing experience and not get aggravated with finding the "right" location to get the view right. Thanks.

 

Yes: and this eye blackout  is why, if we are feeling uncharitable, we may use the term "muddy glass from the muddy glass factory." **  

 

Pentax XLs and XWs will take you to *the light.*

 

The muddy glass factory finally got around to figuring things out and brought out the Delos line.  They're not muddy glass at all.  These too will take you to *the light*.  My only surprise is that Televue hasn't capitalized on Pentax's abandonment of the 30 and 40mm range to round out its Delos line.

 

GN 

 

**Bearing in mind that Al Nagler is an optical designer whose genius revolutionized visual astronomy.  



#12 Lew Zealand

Lew Zealand

    Apollo

  • *****
  • Posts: 1,392
  • Joined: 28 Jun 2004

Posted 20 August 2015 - 11:18 PM

to the OP: people seem to vary in how much the SAEP (spherical aberration of the exit pupil) or "kidney bean blackout" affects them.

 

for me it is an experience equal to having a bug crawling on my cornea.

 

Oh.

 

 

Well that's not so bad, then.  Steady on, old chap.  Stiff upper lip.



#13 penguinx64

penguinx64

    Soyuz

  • *****
  • Posts: 3,928
  • Joined: 12 Nov 2013

Posted 21 August 2015 - 02:12 PM

I have black outs and kidney beaning with almost every eyepiece 25mm or more.



#14 Starman1

Starman1

    Vendor (EyepiecesEtc.com)

  • *****
  • Vendors
  • Posts: 46,815
  • Joined: 23 Jun 2003

Posted 23 August 2015 - 06:01 PM

Blackouts are caused by being closer to the eyepiece than the exit pupil position.

Kidney bean is a form of vignetting caused by SAEP, spherical aberration of the exit pupil.

Here is a better, more in-depth, explanation of how the two are different:

http://www.handprint...O/ae4.html#SAEP

Look especially at the illustrations below the text.

Note that the 31 Nagler has no kidney beaning, but can easily have blackouts.




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.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics