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Delos 17.3---VERY Sad

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#1 SkyRanger

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Posted 30 March 2012 - 09:33 PM

I had first light with my D17.3 tonight in my 8" F6 dob. To my great disappointment, it would NOT come to focus; I needed a mm or so more infocus I did not have. The D6 and 10 are close to parfocal and work fine in my little dob. Am I the only one who did not realize that the D17 was not even close to the other Deloi?

Gordon

#2 johnnyha

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Posted 30 March 2012 - 09:37 PM

No Gordon I have experienced the same thing and a few others have reported it, you do need another 1/4" or so of backfocus. Have you tried screwing the collimation bolts in a little to move your mirror up and get the extra mm?

#3 johnnyha

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Posted 30 March 2012 - 09:38 PM

Post deleted by johnnyha

#4 SkyRanger

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Posted 30 March 2012 - 10:10 PM

I will try adjusting the collimation screws tomorrow night--might get just enough to make it work. Thanks for the suggestion!

Gordon

#5 BillP

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Posted 30 March 2012 - 10:18 PM

According to the TV site's EP Specs sheet, the 17D needs about 1/2" infocus compared to the 6mm and 10mm. The field stop is located about 1/4" above the shoulder of the eyepiece.

#6 seryddwr

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Posted 30 March 2012 - 11:00 PM

If that doesn't work, ScopeStuff has a negative profile 2" to 1.25" adapter that might work.

#7 sniperpride

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Posted 31 March 2012 - 01:11 AM

Here I came to this thread thinking something was wrong with the 17.3
false alarm...

#8 Scott in NC

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Posted 31 March 2012 - 05:39 AM

Whew! Fortunately your situation can be fairly easily remedied. My first thought was that you had dropped it and rolled it down your driveway! :bawling:

#9 Sgt

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Posted 31 March 2012 - 05:57 AM

Yeah I thought you'd dropped it!
... Either that or TV decided to go with Double undercuts or something :smirk:

#10 csa/montana

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Posted 31 March 2012 - 09:41 AM

If that doesn't work, ScopeStuff has a negative profile 2" to 1.25" adapter that might work.


Greg; that might work!

#11 derangedhermit

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Posted 31 March 2012 - 03:06 PM

I'm actually quite steamed about this. Traditionally, all TeleVue 1.25" eyepieces - the Plossls, the Radians, the Naglers, the Panoptics - are parfocal. The exceptions are the 40mm Plossl and, evidently, the Ethos line.

Having parfocal eyepieces is a real convenience to me. This is one way the Delos line falls short of my expectations. I own the 17.3, and I'm surprised and disappointed.

#12 johnnyha

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Posted 31 March 2012 - 03:39 PM

The Ethos line goes the other way - you have to rack the focuser out, sometimes a lot. The new Delos racks IN... so changing between 2" Ethos and Delos 17.3mm could require quite a bit of travel. Luckily bino-friendly scopes are becoming more popular, so achieving focus won't be an issue with most people. One potential problem I can see besides not achieving focus at all, is you might be normally using an extension with your other eyepieces in the bino-friendly scope, but the extension may have to be removed just for the Delos. In binoviewing there is a potential problem in that you may not be able to get the Delos 17.3mm to focus with your lowest power setup, it may require more barlow magnification to achieve focus.

I'll admit I am missing my svelte little 19mm Pans... parfocal with my Brandons... :bawling: :grin:

#13 helpwanted

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Posted 31 March 2012 - 04:08 PM

This disappoints me! I wanted to use all of the Delos, because they would all use the same focus setting in my Paracorr 1. Now I find out the 17.3 will not even come to an optimal setting in the Paracorr. This is just like using an XW in the Paracorr, you GUESS at the sharpest point.

With all the 1.25 eps that TV makes, and this is the only one that is not parfocal with the rest, it just seems like a rush to get to market, without any thought.
Would it have not made more sense to find the longest focal length that would work, and be parfocal? Maybe a 16.5, or an even 17.
I would rather have that, and all my eps parfocal, not to mention able to work in my Paracorr without guessing on the sharpest point.

#14 Scanning4Comets

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Posted 31 March 2012 - 04:21 PM

I was kinda bummed when I found this out too! I WAS going to grab a 17.3mm Delos, but not after finding out you need 1/2" more in travel compared to the 10mm and 6mm Delos eyepieces.

I parfocalized three eyepieces just last week.

The 6mm Delos and 28mm Meade 5000 SWA are super close to being perfectly parfocal while I have my Antares twist lock adapter on the 6mm Delos. All I needed to make the 28mm 5000 SWA and 6mm Delos with antares twist lock adapter parfocal, was use a thin rubber gasket on the 28mm SWA!

The 12mm Nagler T4 just needed one thin rubber gasket and another rubber ring just above it! Thanks to JunoMike, he gave me the idea to use the rubber gasket rings! I looked in my junk drawer and there were a whole bunch in there from a while back just sitting there! Great thing is that they don't mark up the eyepieces like a 2" metal parfocal ring does with the small set screw.

Here are pics of my three eyepieces which are now all parfocal with each other....zero refocusing needed!

Cheers,

Attached Files



#15 Scott in NC

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Posted 31 March 2012 - 04:52 PM

Hey Mark--nice pic. I seem to recognize one of those 2" adapters; glad it came in handy for you! :grin: Seriously though, I wouldn't have thought to use rubber gasket rings. Where did you find them (and no, I don't mean in your junk drawer, I mean originally)?

#16 Scanning4Comets

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Posted 31 March 2012 - 05:00 PM

Hi Scott! yes indeed! Thanks!!! :grin: That is your adapter you sent to me! It sure did come in handy! As you can see, there isn't much 2" barrel space left on my 12mm Nagler T4 when parfocalizing comes into play! The black barrel extender makes it all good now! :jump:

Thanks to you Sir!
Now back to the 17.3mm Delos thread peeps! I have to admit, the 17.3mm Delos looks rather sexy. :thankyou: :bigblush: :flower: :yay:

Cheers,

#17 Scott in NC

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Posted 31 March 2012 - 05:07 PM

I'd like to express my apologies to the OP. I just realized that my comment and question to Mark could be construed as thread hijacking, and that was not my intention at all. I'll let you return to the subject at hand re: the 17.3mm Delos, and will conduct any further non-Delos commentary via PM. Sorry!
:flower:

#18 Starman1

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Posted 31 March 2012 - 05:25 PM

If you use a Paracorr, all your eyepieces will be parfocal--only the tunable top goes in and out.

But, I understand the 17.3 is like the 31 Nagler and 21 Ethos in a Paracorr I--the tunable top simply doesn't move in far enough to find the optimum position for the eyepiece.

It would if it were a 2" eyepiece--it's the massive amount of pull-back that occurs in the eyepiece because it's 1-1/4".

It needs about 1/2" more in-travel on the tunable top than the Type 6 Naglers.

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.

In the Paracorr II, the Type 6 Naglers use setting D on the Paracorr, and setting A is the farthest in position, another 0.3" in from the D setting, so still 0.2" shy of moving far enough in to get to the optimum position.

The obvious answer is a 1.25" adapter that's thinner than the one in the Paracorr. Since it's already a very thin adapter, the following would be a good possibility as a solution:
http://www.astrosyst...ieceadapter.htm

Though the large diameter eyepiece wouldn't insert in this adapter all the way to the sunken shoulder, it WOULD move in closer than the top of a normal 1.25" adapter.
And since what you really need is 3/8" on the original Paracorr and a smaller amount on the Paracorr II, I'm sure this adapter would help to provide some extra amount of inward focuser travel.

And, there's no reason this adapter wouldn't work in any 2" focuser to gain inward focuser travel if you don't use a Paracorr.

NOTE: I do not know what the bottom of the fat barrel diameter is on the 17.3 Delos. It is larger than the 6mm and 10mm. If it does NOT insert into the deep-set adapter far enough for the 1.25" barrel on the eyepiece to insert into the 1.25" hole in the adapter, THEN THIS ADAPTER WILL NOT WORK. I would measure the outside diameter of the 17.3mm Delos just above the 1.25" barrel and compare it to the inside diameter of the deep-set adapter BEFORE I bought the adapter just to be sure it would work.
If the eyepiece body inserts into the adapter even a millimeter, that would be enough to help out the problem of inward focuser travel.

If you use a 1.25" focuser, though, the 17.3mm will focus nearly 1/2" further in than a lot of 1.25" eyepieces.

#19 derangedhermit

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Posted 05 April 2012 - 07:40 PM

I'm not very happy when the solution to a product problem starts like this:
1. Buy a lathe that can turn aluminum
2. Learn to use it.
3. Make your own product to solve the problem.
To get the reported 1/2" infocus, you would need a 2-1.25" adapter that accepted 1.9" wide eyepieces down to that .5" level. More than 0.5" cannot be done in a 2" adapter or focuser, the eyepiece gets wider than 2" after just over 0.5". I guess you can make a 1.25-2" adapter with 0.05 walls, or add rings 0.5" up on the other Delos. But I have not yet found parfocal rings that fit the inletted ("safety") part of the eyepiece chrome section, only the standard 1.25" diameter ones.

#20 Richard Low

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Posted 05 April 2012 - 10:51 PM

If you use a Paracorr, all your eyepieces will be parfocal--only the tunable top goes in and out.

But, I understand the 17.3 is like the 31 Nagler and 21 Ethos in a Paracorr I--the tunable top simply doesn't move in far enough to find the optimum position for the eyepiece.

It would if it were a 2" eyepiece--it's the massive amount of pull-back that occurs in the eyepiece because it's 1-1/4".

It needs about 1/2" more in-travel on the tunable top than the Type 6 Naglers.

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.

In the Paracorr II, the Type 6 Naglers use setting D on the Paracorr, and setting A is the farthest in position, another 0.3" in from the D setting, so still 0.2" shy of moving far enough in to get to the optimum position.

The obvious answer is a 1.25" adapter that's thinner than the one in the Paracorr. Since it's already a very thin adapter, the following would be a good possibility as a solution:
http://www.astrosyst...ieceadapter.htm

Though the large diameter eyepiece wouldn't insert in this adapter all the way to the sunken shoulder, it WOULD move in closer than the top of a normal 1.25" adapter.
And since what you really need is 3/8" on the original Paracorr and a smaller amount on the Paracorr II, I'm sure this adapter would help to provide some extra amount of inward focuser travel.

And, there's no reason this adapter wouldn't work in any 2" focuser to gain inward focuser travel if you don't use a Paracorr.

NOTE: I do not know what the bottom of the fat barrel diameter is on the 17.3 Delos. It is larger than the 6mm and 10mm. If it does NOT insert into the deep-set adapter far enough for the 1.25" barrel on the eyepiece to insert into the 1.25" hole in the adapter, THEN THIS ADAPTER WILL NOT WORK. I would measure the outside diameter of the 17.3mm Delos just above the 1.25" barrel and compare it to the inside diameter of the deep-set adapter BEFORE I bought the adapter just to be sure it would work.
If the eyepiece body inserts into the adapter even a millimeter, that would be enough to help out the problem of inward focuser travel.

If you use a 1.25" focuser, though, the 17.3mm will focus nearly 1/2" further in than a lot of 1.25" eyepieces.


From what i am reading, it seems that Televue did not make the Delos 17.3mm work at the optimum position on the Paracorr II because there is not enough in-travel focus (beyond "A" setting). This is not something I would expect of two products from the same leading company. I can understand the disappointment. I am sure Televue will sort this out.

Thankfully my whole XW series work at the Paracorr II's "A" setting together with the ZAO-IIs.

#21 Starman1

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Posted 06 April 2012 - 12:53 AM

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.

#22 ThreeD

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Posted 06 April 2012 - 12:58 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. :foreheadslap:

#23 ThreeD

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Posted 06 April 2012 - 01:07 AM

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. ;)

#24 Jeff Morgan

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Posted 06 April 2012 - 09:44 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?

#25 Starman1

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Posted 06 April 2012 - 09:59 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?


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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