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Equipment Discussions >> Eyepieces

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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
24mm Brandon: I think I just figured it out.
      #5502894 - 11/03/12 07:58 PM

The 24mm Brandon is the "odd man out" in that it has a wider AFOV than the rest. Though they're all putatively 50-degrees, they aren't really. I suspect the "average" is around 43-degees and the 24mm is closer to 53-degrees. Problem is, in anything approaching a "fast" scope (anything faster than f/8) the outer portion of the field is quite astigmatic (:barf:).

But...remember the Dakin! The matched Barlow for the Brandon line is the 2.4x Dakin Barlow. When you mate the 2.4x Dakin with the 24mm Brandon, you're operating at 10mm with a 53-degree fairly well corrected AFOV with ~19mm of eye relief.

In other words, it was a 10mm Radian long before there was a 10mm Radian.

- Jim


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houser23
sage


Reged: 10/26/09

Loc: Rocklin, CA
Re: 24mm Brandon: I think I just figured it out. new [Re: jrbarnett]
      #5502927 - 11/03/12 08:18 PM

I think applause is in order.

Edited by Scott in NC (11/03/12 10:55 PM)


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johnnyha
Postmaster
*****

Reged: 11/12/06

Loc: Sherman Oaks, CA
Re: 24mm Brandon: I think I just figured it out. new [Re: houser23]
      #5502976 - 11/03/12 08:55 PM

Nice! The Delos are also just Panoptics in TV barlows and the 4.7 Ethos looks suspiciously like the 13 Ethos in a 2.5X Powermate.

And pssst... the T6 line and 1.25" XW line are each just one eyepiece, with the field lens pulled further and further away from the eye lens for more mag...


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pstarr
Carpal Tunnel
*****

Reged: 09/17/04

Loc: NE Ohio
Re: 24mm Brandon: I think I just figured it out. new [Re: jrbarnett]
      #5503017 - 11/03/12 09:13 PM

So then if you spend $235.00 on the 24mm Brandon and another $185.00 on a Dakin Barlow, you will almost get the equivalent of a 10mm Radian. The fov and eye relief will just be smaller. Huh.

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Jim Rosenstock
Postmaster
*****

Reged: 07/14/05

Loc: MD, south of the DC Nebula
Re: 24mm Brandon: I think I just figured it out. new [Re: jrbarnett]
      #5503085 - 11/03/12 10:08 PM

While I'm not naturally drawn to barlows, I gotta admit the Dakin 2.4X also works magic with my Brandon 16 and 12. Oh, I'll still prefer my Brandon 8, 6, and UOHD 5, but for sharing views with my eyeglasses-wearing friends, the Dakined longer-focus Brandons don't give up much!

Also I'm fond of the 2.8X Klee Barlow for more "in-between" magnifications--try that with an old 28mm Ortho or RKE!

Cheers,

Jim


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Jeff Morgan
Postmaster
*****

Reged: 09/28/03

Loc: Prescott, AZ
Re: 24mm Brandon: I think I just figured it out. new [Re: jrbarnett]
      #5503161 - 11/03/12 11:04 PM

Quote:


In other words, it was a 10mm Radian long before there was a 10mm Radian.

- Jim




Radian?! Yuck.

Some time ago it occurred to me that the 24 Brandon/2.4 Dakin combo was at least a 10 Delos long before there was a 10 Delos.

Edited by Jeff Morgan (11/03/12 11:10 PM)


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dscarpa
Post Laureate
*****

Reged: 03/15/08

Loc: San Diego Ca.
Re: 24mm Brandon: I think I just figured it out. new [Re: jrbarnett]
      #5503174 - 11/03/12 11:20 PM

For $80 less than the Brandon-Dakin barlow one could get a Delos at the sale price. David

Edited by dscarpa (11/03/12 11:24 PM)


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Scott in NCModerator
Mad Hatter
*****

Reged: 03/05/05

Loc: NC
Re: 24mm Brandon: I think I just figured it out. new [Re: Jeff Morgan]
      #5503180 - 11/03/12 11:28 PM

Quote:


Some time ago it occurred to me that the 24 Brandon/2.4 Dakin combo was at least a 10 Delos long before there was a 10 Delos.




I think I'd still rather have the Delos, as it'll have a MUCH wider AFOV than the Brandon/Dakin combo.


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: 24mm Brandon: I think I just figured it out. new [Re: dscarpa]
      #5503202 - 11/03/12 11:52 PM

Yeah, but then you'd be stuck with a Delos and not have either the Brandon or Dakin Barlow.

- Jim


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: 24mm Brandon: I think I just figured it out. new [Re: pstarr]
      #5503204 - 11/03/12 11:53 PM

What I meant to say was "like a 10mm Radian, only not all sucky like that".

- Jim


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dscarpa
Post Laureate
*****

Reged: 03/15/08

Loc: San Diego Ca.
Re: 24mm Brandon: I think I just figured it out. new [Re: jrbarnett]
      #5503309 - 11/04/12 01:45 AM

But then again the Delos isn't the least bit sucky. David

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johnnyha
Postmaster
*****

Reged: 11/12/06

Loc: Sherman Oaks, CA
Re: 24mm Brandon: I think I just figured it out. new [Re: jrbarnett]
      #5503334 - 11/04/12 01:25 AM

Quote:

Yeah, but then you'd be stuck with a Delos and not have either the Brandon or Dakin Barlow.

- Jim





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johnnyha
Postmaster
*****

Reged: 11/12/06

Loc: Sherman Oaks, CA
Re: 24mm Brandon: I think I just figured it out. new [Re: jrbarnett]
      #5503335 - 11/04/12 01:26 AM

Quote:

Yeah, but then you'd be stuck with a Delos and not have either the Brandon or Dakin Barlow.

- Jim







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Rick Woods
Postmaster
*****

Reged: 01/27/05

Loc: Inner Solar System
Re: 24mm Brandon: I think I just figured it out. new [Re: johnnyha]
      #5503356 - 11/04/12 02:12 AM

The only solution is to get them all.

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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: 24mm Brandon: I think I just figured it out. new [Re: Rick Woods]
      #5503631 - 11/04/12 09:33 AM

Rick, you make 'em sound like Pokemon.



- Jim


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Rick Woods
Postmaster
*****

Reged: 01/27/05

Loc: Inner Solar System
Re: 24mm Brandon: I think I just figured it out. new [Re: jrbarnett]
      #5504478 - 11/04/12 08:06 PM

Hey, it's not my money!

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Metalmanstan
super member


Reged: 07/02/12

Loc: Oneonta, NY
Re: 24mm Brandon: I think I just figured it out. new [Re: Rick Woods]
      #5504511 - 11/04/12 08:26 PM

So because I have a f/4.9 telescope I have to probably spend more on the eyepieces then I did on the scope? Just got itbsobim just learning, please bare with me

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Scott in NCModerator
Mad Hatter
*****

Reged: 03/05/05

Loc: NC
Re: 24mm Brandon: I think I just figured it out. new [Re: Metalmanstan]
      #5504565 - 11/04/12 09:03 PM

Quote:

So because I have a f/4.9 telescope I have to probably spend more on the eyepieces then I did on the scope?




You *can*, but you really don't *have to*. An inexpensive set of Plossls will do just fine for now, and if you decide to stick with the hobby and wish to upgrade someday, there will be plenty of opportunity to do that later.


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Keith
sage
*****

Reged: 05/14/05

Loc: Costa Mesa, CA USA
Re: 24mm Brandon: I think I just figured it out. new [Re: Metalmanstan]
      #5504734 - 11/04/12 10:41 PM

Quote:

So because I have a f/4.9 telescope I have to probably spend more on the eyepieces then I did on the scope? Just got itbsobim just learning, please bare with me




Back in the day that was the case, but nowadays there are suitable alternatives, explore scientific comes to mind as a good value that handles fast newtonians well, 82deg especially. Wide fields come in handy if it is a dob, but if it is on a tracking platform or driven mount, good plossls work fine until you get spoiled by darth nagler and emperor ethos. And even then, Explore scientific to the rescue, $299 for a waterproof 100deg 20mm eyepiece, much less than half the price of the ethos, and at least 80% of the performance. $100 a piece for 1.25" 82degs 4.7,6.7,8.8,11,14mm is a bargain too. If I didn't already have a mixed bag of older meade UWA, Nagler and Pentax, I would snatch them up. Note that I DO have both 14mm and 20mm ES100's, and they curb my ethos lust quite well. I have not yet experienced Delos, since I was pulled out of the game just before they hit the market.


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LDb
Pooh-Bah
*****

Reged: 02/01/08

Loc: Cleveland, Ohio
Re: 24mm Brandon: I think I just figured it out. new [Re: Keith]
      #5509214 - 11/07/12 11:35 PM

Well Jim,

Once again your insight uncovers an important piece of the riddle of the Brandons.

The Dakin has proven to be an extraordinary barlow (and the only one I have kept) since I got mine in 1985. It's match to the 24mm with its wider FOV is amazing and it does make all of the Brandons a whole "new" set with intermediate mags and virtually no loss or "interference" with the image. Just another one of those interesting little things about how good these "old" deisgns are.

Never giving mine up.

As ever, a humble acolyte of Ordo Brandonensis


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Jeff B
Carpal Tunnel
*****

Reged: 12/30/06

Re: 24mm Brandon: I think I just figured it out. new [Re: LDb]
      #5510117 - 11/08/12 03:10 PM

So somebody please explain to me what exactly is a "matched" barlow.

What does it "match"?

Jeff


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Rick Woods
Postmaster
*****

Reged: 01/27/05

Loc: Inner Solar System
Re: 24mm Brandon: I think I just figured it out. new [Re: Jeff B]
      #5510434 - 11/08/12 07:36 PM

According to the post, it matches the 24mm Brandon. I interpret that as meaning the combination is greater than the sum of the parts. Or something like that.
The Dakin, with its 2.4x magnification, is intended to complement the Brandons by making a whole new set of eyepieces with no duplications.

I've got a Dakin, but I confess I haven't used it hardly at all (you don't need a barlow in a big SCT), so I can't say from personal experience.


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Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: 24mm Brandon: I think I just figured it out. new [Re: Rick Woods]
      #5510518 - 11/08/12 08:46 PM

I hardly ever use a Barlow any more; virtually never for deep sky, hardly ever for planets/Moon. But I do screw on a Barlow lens cell in order to compensate for not enough in-focus when I use a binoviewer or filter wheel on my Newts. Other than that, I'd rather utilize individual eyepieces. I've recently sold a couple of my Barlows. Just wasn't using them.

Mike


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Jeff B
Carpal Tunnel
*****

Reged: 12/30/06

Re: 24mm Brandon: I think I just figured it out. new [Re: Rick Woods]
      #5510563 - 11/08/12 09:11 PM

Quote:

According to the post, it matches the 24mm Brandon. I interpret that as meaning the combination is greater than the sum of the parts. Or something like that.
The Dakin, with its 2.4x magnification, is intended to complement the Brandons by making a whole new set of eyepieces with no duplications.

I've got a Dakin, but I confess I haven't used it hardly at all (you don't need a barlow in a big SCT), so I can't say from personal experience.




Ok, so what optical abberations does it correct, if any?


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Rick Woods
Postmaster
*****

Reged: 01/27/05

Loc: Inner Solar System
Re: 24mm Brandon: I think I just figured it out. new [Re: Jeff B]
      #5511006 - 11/09/12 03:36 AM

That, I don't know.

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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: 24mm Brandon: I think I just figured it out. new [Re: Jeff B]
      #5511485 - 11/09/12 11:46 AM

The introduction of a Barlow or Smythe Lens (either one) corrects for off-axis astigmatism in faster scopes. In fact, that's one of the main reasons "modern" eyepieces like Naglers handle a fast light cone better than "traditional" ones; the design incorporates a Barlow-like element.

Regards,

Jim


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