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Equipment Discussions >> Eyepieces

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

Reged: 06/24/03

Loc: Los Angeles
Re: Delos 17.3---VERY Sad new [Re: Richard Low]
      #5158556 - 04/06/12 01:53 AM

Quote:

Quote:

Since the Type 6 Naglers use setting 4 on the original Paracorr, you have only 1/8" additional you can move the Paracorr in from there--3/8" shy of the full 1/2" you need to move in but far from bad. Being 3/8" away from the optimum setting is more than the Nagler 31 and Ethos 21.


There is a 0.63" delta of the focal plane position between T6N and the N31 while it is only 0.48" between the the T6N and the D17.3. Ergo using setting 5 on a Paracorr 1 will be closer to ideal for the D17.3 than it is for the N31. While not ideal, 5 still helps for the N31 and it should work a bit better for the D17.3 plus the latter isn't in need of as much help to begin with since the FOV is smaller.



You are forgetting that the 31 Nagler is 2" and inserts into the Paracorr a lot more than a 1.25" eyepiece, whereas the Delos and nagler 6's are 1.25" eyepieces.
Ergo, the setting 5 on the Paracorr 1 is only 1/8" away from the optimum setting--not much.
On the other hand Setting 5 is 3/8" shy of far enough in to optimize the 17.3 Delos. The paracorr I has an adapter which is .379" tall. If you can eliminate this height, then setting 5 may be OK for the 17.3 Delos. If the adapter I previously referred to works, it may allow another 3/8" inward movement due to its lower height in the first place and, possibly, a slight inward movement of the eyepiece from a simple shoulder.
The Nagler 6 eyepieces have a 0.48" greater out focus than the 17.3 Delos, which is approximately the whole range of the Paracorr I's tunable top. Unfortunately the Nagler 6's use the 1.25" adapter in setting 4, 1/8" shy of the in-most setting. But you need not one more inward setting, but 4 in order to optimize the 17.3 Delos.
Shortening the 1.25" adapter will help. Add that to moving the tunable top in some, and you will be about as far from optimum as the 31 Nagler and 21 Ethos in the same Paracorr--not very much and quite tolerable.

It doesn't surprise me that TeleVue would make an eyepiece not optimized by their own Paracorrs, either I or II. I think one of the reasons for the greater adjustment range on the Paracorr II was because TeleVue had eyepieces not optimized by the Paracorr I. It wouldn't surprise me if, in the future, there was even a Paracorr III to accommodate eyepieces not yet even in production. It's always a race to accommodate designs as they come out.


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ThreeD
Pooh-Bah


Reged: 12/23/08

Loc: Sacramento suburbs
Re: Delos 17.3---VERY Sad new [Re: Richard Low]
      #5158562 - 04/06/12 01:58 AM

Thus creating a need for the Paracorr Type 3 that will be announced at NEAF much to the chagrin of those who invested in the Type 2 over the last year.

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ThreeD
Pooh-Bah


Reged: 12/23/08

Loc: Sacramento suburbs
Re: Delos 17.3---VERY Sad new [Re: Starman1]
      #5158567 - 04/06/12 02:07 AM

Quote:


You are forgetting....


Yup I realised this a few short minutes after I did my post so I deleted it. Unfortunately you were on top of things and were already responding.

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Jeff Morgan
Postmaster
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Reged: 09/28/03

Loc: Prescott, AZ
Re: Delos 17.3---VERY Sad new [Re: Starman1]
      #5158943 - 04/06/12 10:44 AM

While I don't use a Paracorr, I find this interesting because I am building a truss scope. In the next month or two it is going to be time to start cutting aluminum, and I certainly want to accommodate my shiny new 17.3 Delos.

From what I gather, the infocus is quite similar (almost identical) to the 31 Nagler. Is this correct?


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Starman1
Vendor (EyepiecesEtc.com)
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Reged: 06/24/03

Loc: Los Angeles
Re: Delos 17.3---VERY Sad new [Re: Jeff Morgan]
      #5158975 - 04/06/12 10:59 AM

Quote:

While I don't use a Paracorr, I find this interesting because I am building a truss scope. In the next month or two it is going to be time to start cutting aluminum, and I certainly want to accommodate my shiny new 17.3 Delos.

From what I gather, the infocus is quite similar (almost identical) to the 31 Nagler. Is this correct?




Only if you ignore the thickness of the 1.25" adapter.

The 31 Nagler has its focal plane 0.38" above the seat of the barrel.
The 17.3 Delos has its focal plane 0.23" above the seat of the barrel.

IF your 1.25" adapter is 0.38 - 0.23 = 0.15" thick, then the two eyepieces would be parfocal.

However, most 1.25" adapters are quite a bit thicker than 0.15". A relatively thin one is about 0.25".

That means the "effective" distance the Delos focal plane is above the focuser is 0.23" plus the thickness of the adapter.

That is likely to exceed the 0.38" for the 31 Nagler, so the highest likelihood is that the 17.3mm Delos will require additional inward movement of the focuser to focus, compared to the 31 Nagler. How much additional in-focus will depend on the thickness of your adapter.

In a Moonlite focuser with a Moonlite adapter, the adapter's "lip" is so thin the 17.3mm Delos might require a bit more OUT focus compared to the 31 Nagler. But that is an exceptional situation.


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Deep13
Carpal Tunnel
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Reged: 01/25/05

Loc: NE Ohio
Re: Delos 17.3---VERY Sad new [Re: Starman1]
      #5160894 - 04/07/12 02:54 PM

Scratch this one off the list. Serious design flaw. So now the question is, 16 or 17 Nagler?

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Ava
sage


Reged: 11/30/11

Loc: Sweden
Re: Delos 17.3---VERY Sad new [Re: Deep13]
      #5160905 - 04/07/12 03:03 PM

Baader sells a 2"-1.25" adapter that would fit the bill, only 1mm optical path length (less than 0.04"). Part #15A, you can check it out here:

http://www.teleskop-express.de/shop/product_info.php/language/en/info/p767_Baader--15A-2--Steckhuelse-auf-1-25----nur-1mm-optische-Baulaenge.html

Can be used as adapter or permanent solution for a specific eyepiece. Should be available in any US shop that sells Baader adapters I guess.

//Anders


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ed_turco
Pooh-Bah
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Reged: 08/29/09

Loc: Lincoln, RI
Re: Delos 17.3---VERY Sad new [Re: ThreeD]
      #5161076 - 04/07/12 05:08 PM

Quote:

Thus creating a need for the Paracorr Type 3 that will be announced at NEAF much to the chagrin of those who invested in the Type 2 over the last year.




It is a very clever business model that plans for incremental improvements over the years. Does this mean that the designer didn't get it right the first time?

Why?

Surprised this hasn't come up before.



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helpwanted
Post Laureate
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Reged: 07/04/07

Loc: Phoenix, AZ
Re: Delos 17.3---VERY Sad new [Re: ed_turco]
      #5161245 - 04/07/12 07:18 PM

Great, TV is going to mimic Apple and get us to but a new Paracorr every year with our iPads & iPhones?
I agree with skipping this 17.3 and just wait and hope for a parfocal 12.


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derangedhermit
Pooh-Bah


Reged: 10/07/09

Loc: USA
Re: Delos 17.3---VERY Sad new [Re: helpwanted]
      #5161636 - 04/08/12 02:01 AM

TV should offer a 1.25"-2" adapter designed to make the 17mm parfocal with all the other 1.25 eyepieces (except Ethos), when the others are used with some "standard height" (TV I'm sure) adapter. And maybe not charge the typical startling amount for it, as a way to show some goodwill. Actually they should start putting it in the box with the eyepiece.

I'll check their return policy. I've decided maybe I just don't want to mess with the thing, over this one issue.


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Jeff Morgan
Postmaster
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Reged: 09/28/03

Loc: Prescott, AZ
Re: Delos 17.3---VERY Sad new [Re: derangedhermit]
      #5161843 - 04/08/12 08:56 AM

Quote:


I'll check their return policy. I've decided maybe I just don't want to mess with the thing, over this one issue.




Perspective.

I seem to have an instinctive need to play with focus whenever I change eyepieces. Since I have a nice focuser, parfocal has never been an issue for me.

OTOH, getting a great eyepiece is of great importance to me. Less than 3/16" more infocus than the 31 Nagler? I can manage that. I'll just make my Newtonian truss poles a little bit shorter, and of course no issue at all on the refractor. I can't imagine SCT owners will have any issues at all.


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helpwanted
Post Laureate
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Reged: 07/04/07

Loc: Phoenix, AZ
Re: Delos 17.3---VERY Sad new [Re: Jeff Morgan]
      #5162193 - 04/08/12 01:29 PM

It's not the parfocal for me, it the fact that it doesn't have a Paracorr position.
If I have to settle with "close enough" in the paracorr, I'll just keep my XWs.


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sniperpride
super member


Reged: 01/04/12

Re: Delos 17.3---VERY Sad new [Re: helpwanted]
      #5162392 - 04/08/12 03:59 PM

I dont use paracorr for my Delos, I find it well corrected, and at 72* fov I dont detect coma in my f4.5

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Pollux556
Pooh-Bah
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Reged: 12/14/08

Re: Delos 17.3---VERY Sad new [Re: SkyRanger]
      #5162808 - 04/08/12 10:07 PM

I am reminded that some Speers Waler serie 1 ep had this problem in some Dobs

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Richard Low
professor emeritus
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Reged: 11/27/05

Loc: 1 deg N, GMT+8hrs
Re: Delos 17.3---VERY Sad new [Re: Pollux556]
      #5162892 - 04/08/12 11:10 PM

I am keeping my XWs. I also have the Ethos to fill in the focal length at 17mm. Sometimes when i observed through the Ethos with my glasses on, the Afov is around 70 degrees, so this make up for the Delos 17.3

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johnnyha
Postmaster
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Reged: 11/12/06

Loc: Sherman Oaks, CA
Re: Delos 17.3---VERY Sad new [Re: Richard Low]
      #5163713 - 04/09/12 02:35 PM

There is a very real chance if you have a short-tube "bino-friendly" refractor and you normally employ an extension to reach focus, that you may have to remove the extension for this one eyepiece. I did not have this problem but the increasing distance between the focal point of the Ethos and the 17.3 Delos is worrisome.

Frankly I had minor problems with blackouts (maybe its my eyes getting older) but primarily I did not like the weight in my binoviewers compared to my 19mm Pans. The 19mm Pans won out for me. Of course they only have 13mm eye relief but I don't view with my glasses on and I find the Pan most comfortable for me.


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dscarpa
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Reged: 03/15/08

Loc: San Diego Ca.
Re: Delos 17.3---VERY Sad new [Re: SkyRanger]
      #5163760 - 04/09/12 03:11 PM

I've had a 17.3 Delos for a couple of weeks and it's already one of my favorites up there with my Ethos and XWs. Barlowed it's very easy to use with images of the Moon, Mars and Saturn being truly excellent. I have cats and a refractor. I did notice it wasn't parfocal with my 24 Pan. The Delos and Pan do make a very nice DSO team well worth a bit of refocus for me.David

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mark8888
Carpal Tunnel


Reged: 09/24/10

Re: Delos 17.3---VERY Sad new [Re: dscarpa]
      #5164045 - 04/09/12 07:12 PM

Quote:

I have cats and a refractor. I did notice it wasn't parfocal with my 24 Pan.




With your refractor, could you estimate how much you had to turn the focuser to go from the 24pan to the 17.3 Delos?


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Scanning4Comets
Markus
*****

Reged: 12/26/04

Loc: Ontario, Canada
Re: Delos 17.3---VERY Sad new [Re: Richard Low]
      #5164061 - 04/09/12 07:23 PM

As I stated in the beginning of this thread, I was kinda bummed out, but parfocalizing eyepieces is simple! Go see my pic on page one of this thread! I said I wouldn't get the 17.3mm Delos because of the extra focus travel needed, but after some thought, it is a really easy fix!

First, you put the eyepiece in your focuser that needs the most "in" travel on your focuser. After that, remove that eyepiece and just leave the focuser exactly where it is. Now, take your other eyepieces and slowly put them into the focuser until you get a good focus and use the set screws, or compression ring to lock the next eyepieces in place and use a thin erasable marker to mark the eyepiece barrel just above the lip of your focuser. All you have to do now is use strong rubber gaskets to put just above the mark you made on your other eyepiece barrels!!!....Now when you use your eyepieces, they will all focus at the same distance in your focuser !!!

If you use a paracorr, well, I guess that maybe another story, LOL!





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Mr. Bill
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Reged: 02/09/05

Loc: Northeastern Cal
Re: Delos 17.3---VERY Sad new [Re: Scanning4Comets]
      #5165329 - 04/10/12 02:27 PM

Just a reminder....TV website ep specs page gives fieldstop location referenced from the ep shoulder for all their current eps.

Use it and there will be no more surprises after ordering TV eps.



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