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Equipment Discussions >> Eyepieces

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Keith
sage
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Reged: 05/14/05

Loc: Costa Mesa, CA USA
Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: gezak22]
      #5509322 - 11/08/12 02:03 AM

Admiral Ackbar of Mon Calimari has 3" binoviewers, but he also has eyes on the side of his head.

IT'S A TRAP!


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BillP
Postmaster
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Reged: 11/26/06

Loc: Vienna, VA
Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: gezak22]
      #5509854 - 11/08/12 12:14 PM

Quote:

The real question here is how are we going to use these in bino mode?




Easy...one eye at a time


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Shneor
scholastic sledgehammer
*****

Reged: 03/01/05

Loc: Northern California
Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: Keith]
      #5510045 - 11/08/12 02:12 PM

Quote:

how much for your 9mm ES100? =)



Not selling that yet - I can still use it in my 6" f/5 reflector; the 120 is too heavy for that telescope.

Clears,


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Shneor
scholastic sledgehammer
*****

Reged: 03/01/05

Loc: Northern California
Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: Jon Isaacs]
      #5510048 - 11/08/12 02:18 PM

Quote:




Jon



Not necessarily true. The 9mm ES120° shows pinpoint stars from center to edge in my f/4 without any correction needed. It apparently has a quite different design. Unfortunately, as far as I know, only three CN members have one of these, but several observers have viewed through mine. All were amazed by the sharpness across the entire field.

Clears,
Shneor




We have been through this one before with other eyepieces... The 30mm Widescan II comes to mind.

Coma is there to be seen at F/4, the coma free region is 1.4mm, the approximate field stop diameter of the 9mm 120 degree eyepiece is 19mm, that's a lot of room for coma. I have a hard time believing moving a bright star like Rigel to the edge of the field would provide a nice round and still clean primary and secondary.

If an eyepiece truly eliminates coma in an F/4 Newtonian, then the reverse coma necessary to do so would be visible in a coma free telescope...

Jon Isaacs



Sorry Jon, it's the same result in a 4" f/5 refractor. You can complain as much asyou wish, but the results are clear. I don't know how they did it, but they did...I believe Sixela has suggested how they might have accomplished this - see this thread: http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/4866855/page...

Clears,


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Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: Shneor]
      #5510292 - 11/08/12 05:23 PM

Alexis talked about angular magnification distortion versus rectilinear distortion, not coma. Coma is an aberration of the paraboloidal mirror, and is more visible and severe the wider the apparent field, so if this eyepiece has built-in coma correction, and you imply it does, then it is unusable in refractors and catadioptrics.
That seems strange for JOC to do that, but it's certainly possible to do it.

Edit: One other user used this in a Paracorr with good results. I have a hard time believing it has built-in coma correction. therefore.

Edited by Starman1 (11/08/12 05:25 PM)


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sixela
Postmaster
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Reged: 12/23/04

Loc: Boechout, Belgium
Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: Keith]
      #5510319 - 11/08/12 05:40 PM

Quote:

C11/14 and Meades 10/12/14 all have a 3" thread on the rear cell. Hence the peterson eye opener option. On a standard LX200 with microfocuser, there is a step down ring to standard 2" threads that has about 1.5" clear aperture, so widefield 2" eps get light loss at the edges. Taking off that step down ring, and attaching a visual back or focuser directly to the 3" rear cel, opens the aperture to the full 2" and then some. So all it takes is a 3" visual back and diagonal (not common) and theoretically this could work. Since the 11" and the 14" celestron both use the same thread, it is already possible to add a 3" JMI or optec focuser to the scope, so all that would be needed was the diagonal. I would be interested to see a field lens pic of that monster 30, to see how much of the 3" field it is using. Since the light cone is a narrow f10, I have a feeling this could work well on even a c11.




You can physically fit it, but given the diameter of the central baffle I doubt the outer field is going to be very well illuminated. Yes, the clear aperture is larger than the field stop but the baffle (especially the front) is also a lot closer to the secondary and the entry pupil...

But it might still be "good enough", of course; we Newt folks use 31T5s without batting an eyelid when the outer field is illuminated 70%, and I was using a FrankenBlast with 2" focuser in which the edge of a 26T5 was only 50% illuminated with pleasing results.


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pbsastro
professor emeritus
*****

Reged: 03/21/07

Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: sixela]
      #5511942 - 11/09/12 04:24 PM

The 3" diag will also be good for 2" eyepieces with big field stop, such as XW40, Pan 41 or Nag31, because those eyepieces cannot be fully illuminated by a 2" diag in refractors even with large focusers.

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johnnyha
Postmaster
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Reged: 11/12/06

Loc: Sherman Oaks, CA
Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: pbsastro]
      #5512055 - 11/09/12 05:50 PM

A 3" eyepiece also has the potential, depending on the size of the eye lens, to be naturally "binoviewed" with both eyes, simply due to the large size of the optic.

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Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: johnnyha]
      #5512091 - 11/09/12 06:13 PM

Quote:

A 3" eyepiece also has the potential, depending on the size of the eye lens, to be naturally "binoviewed" with both eyes, simply due to the large size of the optic.




They have a big 4" eyepiece at Mt. Wilson they call their "binocular" eyepiece.
Of course, unless the exit pupil is 3" wide (!), even these behemoths are mono-vision eyepieces.


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Grava T
Pooh-Bah
*****

Reged: 06/18/08

Loc: Quebec, Canada
Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: Starman1]
      #5512122 - 11/09/12 06:35 PM

Is that even possible? For example; (and I'm just having fun here) an eight inch ocular with a six inch exit pupil for both eyes! Or is that physically impossible?

.965", 1.25", 2", 3", 4", 5",... 8" I see a progression here for our future.


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faackanders2
Carpal Tunnel


Reged: 03/28/11

Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: Jon Isaacs]
      #5512380 - 11/09/12 10:08 PM

Quote:

Quote:

Scott Roberts is reporting on FB that he will soon be field testing one of these. There is a pic and it is enormous. Wow now SI or someone is gonna have to start making more 3 inch focusers for dobs....




Won't be of much use in a fast Dob until someone makes a 3 inch Coma Corrector... The modern F/3 Dobs are using the 21mm Ethos as the widefield because the 31mm Nagler results in an oversized exit pupil...

Jon




I'll bet a 3" paracorr is in the works. And probably a 40mm 82 AFOV, and a 50mm 70 AFOV too.


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faackanders2
Carpal Tunnel


Reged: 03/28/11

Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: gezak22]
      #5512399 - 11/09/12 10:27 PM

Quote:

The real question here is how are we going to use these in bino mode?




Just move your eyes wider apart.


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faackanders2
Carpal Tunnel


Reged: 03/28/11

Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: Grava T]
      #5512405 - 11/09/12 10:32 PM

Quote:

Is that even possible? For example; (and I'm just having fun here) an eight inch ocular with a six inch exit pupil for both eyes! Or is that physically impossible?

.965", 1.25", 2", 3", 4", 5",... 8" I see a progression here for our future.




Hmmm. Would an 8" eyepiece be an eyepiece or a small telescope?


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faackanders2
Carpal Tunnel


Reged: 03/28/11

Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: Darren Drake]
      #5512409 - 11/09/12 10:34 PM

Can someone please post an image?

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Keith
sage
*****

Reged: 05/14/05

Loc: Costa Mesa, CA USA
Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: faackanders2]
      #5512507 - 11/09/12 11:55 PM

I got in trouble for posting an image

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faackanders2
Carpal Tunnel


Reged: 03/28/11

Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: Keith]
      #5512524 - 11/10/12 12:14 AM

Is there a website to look at?

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Keith
sage
*****

Reged: 05/14/05

Loc: Costa Mesa, CA USA
Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: faackanders2]
      #5512569 - 11/10/12 12:49 AM

scott roberts posted it on his facebook feed, and since I mentioned that, I got in trouble and the pic was taken down.

I can't seem to win, and one of these days I am going to finally stop trying


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ThreeD
Pooh-Bah


Reged: 12/23/08

Loc: Sacramento suburbs
Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: Keith]
      #5512603 - 11/10/12 01:33 AM

The picture is still there... In fact, here is the FB posting. Note it is public so you shouldn't need a FB account to see it.

Yup, it's big all right. That's a 2" 18mm on the left and a 1.25" 11mm on the right. Seems to be Argon purged by the little sticker on it.

Edited by ThreeD (11/10/12 01:38 AM)


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GlennLeDrew
Postmaster
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Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: ThreeD]
      #5512628 - 11/10/12 02:21 AM

To answer the question of two-eyed viewing if the exit pupil is large enough. Sure, it can be done, but your tiny pupils will stop down the system aperture accordingly. Suppose the exit pupil is 80mm, the objective is 800mm, and one's eye pupils are 6mm. The entrance pupils will be near opposite sides of the objective, and their aperture would be 6/80 * 800 = 60mm. Not at all efficient use of that 800mm aperture!

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faackanders2
Carpal Tunnel


Reged: 03/28/11

Re: A 30mm 100 degree 3 inch barrel in the works! new [Re: ThreeD]
      #5513217 - 11/10/12 01:44 PM

Humongous. I wonder how many pounds (or Kg) that is?
I know a 3" focuser (& filters) is required, but would it also require a larger secondary mirror. I currently have a 17.5 f4.1 discovery and a 10.1" f4.5 coltour oddessy dobsonians. I look forward to uberwide TFOVs 3" eyepieces would bring. I assume it would be great for M45, M44, M42, North American, Viel, M31/M32/M110, Markarians Chain, and lots of other multiple objects and conjunctions.

Who is the innovator now? Hope I'll be able to afford one.


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