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Televue Pronto Lens Issue - Mold?

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51 replies to this topic

#1 gdjsky01

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Posted 22 May 2019 - 08:42 PM

I have a very nice TV Proto. There has always been this lens issue (I got it used this way - at a discount).

 

The photo shows it best. There are three sites at roughly 120 degrees that look a bit similar... this is the largest.  120 degrees because I assume that where the spacers are.

 

Is this the mold I have heard about so often when talk about lenes in general? I've never encountered it before.

The other picture is not as clear. The first one I got lucky on.

 

Anyways if I keep or sell, I should clean 'whatever it is' off. Next question:

 

Send it to TV?

Or unscrew the retainer, and take my chances? Is there a thread of such things?

 

Best wishes and clear skies!

Jeff

 

 

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#2 Jon Isaacs

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Posted 22 May 2019 - 08:58 PM

Jeff:

 

There is a thread around here about the Pronto.

 

One thing to be aware of is that the early Pronto's were cemented doublets and they have been known to separate.  TeleVue did have replacement objectives and some have separated them and recemented them, there is information in the Classics forum on how to do that.  

 

I don't know what is up with your objective .. it doesn't look too bad right now.

 

Jon


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#3 OldManSky

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Posted 22 May 2019 - 08:58 PM

Jeff G. is that you?  Long time no see :)

 

My vote is to send it to TV.  But that's because when I try to clean "not-normal" things, they get worse.

 

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#4 ngc7319_20

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Posted 22 May 2019 - 09:13 PM

The usual fungus stuff I see looks more like random fibers and filaments.  This looks more organized.  Could be some unusual fungus I suppose.  Or perhaps some chemical process.  

 

I don't recall if these are cemented doublets.  It might be the start of element separation.  See this other thread:

https://www.cloudyni...gnosis-of-lens/

 

I would send it to TeleVue.


Edited by ngc7319_20, 22 May 2019 - 09:14 PM.

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#5 Redbetter

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Posted 22 May 2019 - 10:40 PM

Looks like what was described in the Pronto thread about the earlier objectives' cement failing.  Call Tele Vue.  From what I recall they sold a replacement air spaced objective to address the problem. 



#6 Spikey131

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Posted 23 May 2019 - 07:19 AM

If the scope is working OK, I would not suggest attempting disassembly.

I would suggest calling Televue. You might be able to send them your photos. They are very helpful.

#7 sgorton99

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Posted 23 May 2019 - 07:34 AM

Mine had this all around the outside edge. You can see it in the bottom of this pic. I would probably just leave it.

 

I did call TV about it and my recollection was that it was about $150+ plus shipping both ways to have serviced and they were familiar with the problem these could develop.

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Edited by sgorton99, 23 May 2019 - 07:34 AM.


#8 25585

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Posted 23 May 2019 - 09:14 AM

The usual fungus stuff I see looks more like random fibers and filaments.  This looks more organized.  Could be some unusual fungus I suppose.  Or perhaps some chemical process.  

 

I don't recall if these are cemented doublets.  It might be the start of element separation.  See this other thread:

https://www.cloudyni...gnosis-of-lens/

 

I would send it to TeleVue.

When I bought my Pronto pre-owned, it needed to have the OG professionally cleaned and re-cemented as there was cement dust and stuff all round the edges. Its a lot better now.



#9 ryderc1

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Posted 23 May 2019 - 09:23 AM

One of the advantages of owning a Televue scope is having access to the company's high level of customer support.  If a problem develops there's a qualified and friendly staff to address it for you.  If it were my scope I'd take advantage of that.


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#10 rolo

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Posted 23 May 2019 - 09:25 AM

Looks like it may be within the cement of the elements.


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#11 KerryR

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Posted 23 May 2019 - 01:58 PM

I'm voting for cement failure, too.

I'm sure if you call T.V. and tell them the serial number, they'll be able to tell you if your Pronto has a cemented or air-spaced doublet.

I had my old Genesis serviced by T.V. . It was expensive, but, IMO, very much worthwhile-- they cleaned the elements, replaced the focuser sleeve, shimmed the cell so it'd hold collimation, aligned the optics, cleaned the diagonal, replaced the stripped eyepiece retaining screw on the diagonal and made the screw captive again. (Sadly, I sold this scope shortly after. I miss it dearly).

I wouldn't wait too long on this-- I'm sure T.V's stock of replacement objectives is pretty limited given that the Pronto has long since been discontinued...

On the other hand, if you're good at fixing stuff, it probably wouldn't be too difficult to fix on your own. Toughest part would be separating the elements (if cemented), followed by collimating (just because it requires you to make a simple jig.)


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#12 gdjsky01

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Posted 25 May 2019 - 01:18 AM

Thank you all for the advice... I guess TV it is... Not sure the scope is worth $150 repair unless they are updating the glass to a better ED at the same time making it airspaced.



#13 25585

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Posted 25 May 2019 - 04:54 AM

Thank you all for the advice... I guess TV it is... Not sure the scope is worth $150 repair unless they are updating the glass to a better ED at the same time making it airspaced.

Ask if they can upgrade to a TV 76 lens for you. That would be a big improvement.



#14 KerryR

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Posted 25 May 2019 - 09:00 AM

Thank you all for the advice... I guess TV it is... Not sure the scope is worth $150 repair unless they are updating the glass to a better ED at the same time making it airspaced.

Considering how good the optics in the Pronto's were/are, I think it'd be worth it. While the color correction is not "ED" by modern standards, even though it was originally marketed as such, the scope still performs very competitively.

If it were me, I'd probably investigate re-cementing the elements myself. If it failed, off to T.V. it'd go, no harm no foul.

You should definitely inquire about a TV76 lens group. I suspect the Pronto cell, at 70mm clear aperture, wouldn't be big enough, but it'd still be worth checking out...




 


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#15 buddy ny

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Posted 25 May 2019 - 11:29 AM

Yes

 TV said the 76 cell would fit

But they wont do it. IIRC , For the price of a cleaning.

Why would they. They want u to buy a new 76.

Cost effective

My 3rd pronto is an air spaced doublet..

They complaint about color correction. Is not ad bad ( to my eye) as some would have u believe

Considering how good the optics in the Pronto's were/are, I think it'd be worth it. While the color correction is not "ED" by modern standards, even though it was originally marketed as such, the scope still performs very competitively.

If it were me, I'd probably investigate re-cementing the elements myself. If it failed, off to T.V. it'd go, no harm no foul.

You should definitely inquire about a TV76 lens group. I suspect the Pronto cell, at 70mm clear aperture, wouldn't be big enough, but it'd still be worth checking out...




 

 


Edited by buddy ny, 25 May 2019 - 11:34 AM.


#16 25585

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Posted 25 May 2019 - 02:32 PM

I am going to enquire through my TV dealer if 76 lens (& cel if needed) can be done, and the cost. 



#17 Redbetter

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Posted 25 May 2019 - 03:16 PM

 

They complaint about color correction. Is not ad bad ( to my eye) as some would have u believe

If one can't see violet/blue well, then perhaps.  A friend of mine had one when they were new (Ranger version.)   It had substantial color, much more than I expected when I first looked through one based on the hype at the time.  Made me very skeptical of short refractors being touted as semi-apo, etc. for two decades.  It was sharp otherwise, but not close to the color correction of ED doublets over the past dozen years or so, not even FPL-51 equivalent--which shows obvious color in some configurations like my 110 f/7.

 

But the Pronto is a sharp small achro w/2" focuser that is well set up for rich field and would still have enough value to replace the objective, despite the color.  Jeff already has his Pronto, so he will already appreciate how much or how little color there is.



#18 Jon Isaacs

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Posted 25 May 2019 - 03:19 PM

A few random thoughts:

 

- It is probably not worth paying TeleVue to do it.  There is some good information in the Classics forum on recementing objectives.  

 

- I had a Pronto.  A nice scope but the chromatic aberration was a problem at times.

 

-  The upgrade to a TV-76 probably be more expensive than a complete, used TV-76.  

 

- At this time, the objective does not look that bad to me, I doubt it affects the image. If it were mold, I would be concerned because mold can damage the glass.  But this seems to be a cementing issue and until it affects the image, it is not worth fixing.

 

Jon



#19 Jon Isaacs

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Posted 25 May 2019 - 03:23 PM

If one can't see violet/blue well, then perhaps.  A friend of mine had one when they were new (Ranger version.)   It had substantial color, much more than I expected when I first looked through one based on the hype at the time.  Made me very skeptical of short refractors being touted as semi-apo, etc. for two decades.  It was sharp otherwise, but not close to the color correction of ED doublets over the past dozen years or so, not even FPL-51 equivalent--which shows obvious color in some configurations like my 110 f/7.

 

But the Pronto is a sharp small achro w/2" focuser that is well set up for rich field and would still have enough value to replace the objective, despite the color.  Jeff already has his Pronto, so he will already appreciate how much or how little color there is.

 

According to Roland C., the Pronto/Ranger was based on FK-5. It is barely off the Abbe normal line and offers very little improvement over a standard achromat.

 

With the arrival of the Orion ED-80, scopes using FK-5 pretty much bit the dust.

 

Jon


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#20 Astroman007

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Posted 25 May 2019 - 07:28 PM

Is cement failure a known problem with many older (to the past ten or twelve years) TV refractors, or just the non-apos like the Pronto?



#21 buddy ny

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Posted 25 May 2019 - 07:36 PM

Yes. I agree there is color

I've owned 3 , it's a 30yr old lens & coatings. 30 yr old Design & tech

I've seen the Blues & purples & yellows.  I've seen pixs with the color. I've also seen pixs without. On Luna color is really trippy. Sweeping the stars not so much

What I'm saying is , the 3 I've owned// own  there's color for sure 

Better glass// coatings now a days ,sure I agree with you

 

I just don't think it's so horrible as some folks post .TV sold a lot of them

when using it for rich- field Use such as sweeping around where the color deficiency counts for almost nothing

& the scope is ,as you say tack sharp. 

Semi-Apo ,,I never heard that applied to the Pronto. I started to hear that catch phrase when TV introduced the "85

All in all its still gets press 30yrs later..

 

 

 

 

If one can't see violet/blue well, then perhaps.  A friend of mine had one when they were new (Ranger version.)   It had substantial color, much more than I expected when I first looked through one based on the hype at the time.  Made me very skeptical of short refractors being touted as semi-apo, etc. for two decades.  It was sharp otherwise, but not close to the color correction of ED doublets over the past dozen years or so, not even FPL-51 equivalent--which shows obvious color in some configurations like my 110 f/7.

 

But the Pronto is a sharp small achro w/2" focuser that is well set up for rich field and would still have enough value to replace the objective, despite the color.  Jeff already has his Pronto, so he will already appreciate how much or how little color there is.

 


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#22 Jon Isaacs

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Posted 25 May 2019 - 10:34 PM

Is cement failure a known problem with many older (to the past ten or twelve years) TV refractors, or just the non-apos like the Pronto?

 

Only the early Prontos and Rangers used cemented doublets. I believe the TV-60, 76, 85 101,102, 127 and 140 are all air spaced.

 

Jon


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#23 Starhawk

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Posted 25 May 2019 - 10:56 PM

I'd send this image to TeleVue and see what they say.  It's at least worth asking what upgrading to TV-76 glass would cost.

 

-Rich

I have a very nice TV Proto. There has always been this lens issue (I got it used this way - at a discount).

 

The photo shows it best. There are three sites at roughly 120 degrees that look a bit similar... this is the largest.  120 degrees because I assume that where the spacers are.

 

Is this the mold I have heard about so often when talk about lenes in general? I've never encountered it before.

The other picture is not as clear. The first one I got lucky on.

 

Anyways if I keep or sell, I should clean 'whatever it is' off. Next question:

 

Send it to TV?

Or unscrew the retainer, and take my chances? Is there a thread of such things?

 

Best wishes and clear skies!

Jeff


Edited by Starhawk, 25 May 2019 - 11:41 PM.

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#24 Oldfield

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Posted 26 May 2019 - 12:51 AM

My Ranger suffered from a similar issue.



#25 Joe Bergeron

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Posted 27 May 2019 - 09:28 PM

I’ve had two Prontos, both acquired used. They were beautiful little scopes. The color error was apparent, but the scope was still about as capable as a Questar. I sold the second one only to help finance my Stowaway, which is clearly in a different league. But I wouldn’t mind having another Pronto. 


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