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Restoration of Criterion RV-4 Deluxe

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#51 tim53

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Posted 12 August 2019 - 10:02 AM

I suppose it might be an issue if the scope is a one-off by a well-known amateur or a rare antique. I doubt we’ll ever see a Porter garden telescope refigured, for example. Dynascooes, on the other hand, are comparatively common and were never Meant to be museum pieces (though perhaps someday they may be). 



#52 DAVIDG

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Posted 12 August 2019 - 11:46 AM

I suppose it might be an issue if the scope is a one-off by a well-known amateur or a rare antique. I doubt we’ll ever see a Porter garden telescope refigured, for example. Dynascooes, on the other hand, are comparatively common and were never Meant to be museum pieces (though perhaps someday they may be). 

 I watch over a Porter Garden Telescope and have tested the optics. They are very good but I would have no issue in making a new primary to replace the one that is in it so the scope would be usable or more usable in it present state. Porter design the scope to be used as a telescope to view the Universe. It does no good in my book not to have it work the they is was design

   At Mt Cuba Observatory we have 4" Clark and we use for public nights. The lens had issue and we had it refigured by D&G. Now the public see the views the way Clark meant them to be and we are turning people onto astronomy not off. 

   If your into car restoration you know that you want the car to restored so it runs like it was designed and not so much like it was built because many times there were mistakes. It wasn't meant to be that way so again there is no sin in my book to make it right.

 

                       - Dave 


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#53 ccwemyss

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Posted 12 August 2019 - 12:14 PM

I didn't know it was EITHER restore it faithfully OR make it work well.  To me, you do both to the best level you can.  Why is this even an issue?  

I think the idea being expressed was to first see if it can be made to work well, before investing the effort to make it look good -- i.e., first check to see if it's a pig before trying to put lipstick on it, rather than the reverse. But that assumes the goal is a restoration that achieves a high quality of usability.

 

For a scope that has historical significance, where the goal is to create a museum piece that nobody will look through, then making it work well is less important than making it look good while maintaining originality. 

 

Chip W.  


Edited by ccwemyss, 12 August 2019 - 12:15 PM.


#54 Chuck Hards

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Posted 12 August 2019 - 12:35 PM

I think the idea being expressed was to first see if it can be made to work well, before investing the effort to make it look good -- i.e., first check to see if it's a pig before trying to put lipstick on it, rather than the reverse. But that assumes the goal is a restoration that achieves a high quality of usability.

 

For a scope that has historical significance, where the goal is to create a museum piece that nobody will look through, then making it work well is less important than making it look good while maintaining originality. 

 

Chip W.  

 

And we see so many museum pieces in this forum that the choice is constantly coming up, I guess.  :lol:


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#55 DAVIDG

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Posted 12 August 2019 - 12:37 PM

I didn't know it was EITHER restore it faithfully OR make it work well.  To me, you do both to the best level you can.  Why is this even an issue?  

  Chuck,

    I see many wonderful mechanical restoration  with  great effort being  made to make the scope as original as possible but few in which the optics are addressed. They just seem to be assumed to have no issue.  So in the case of the two  Fecker Celestar  I have restored and now this RV-4, if I restored them to their exact original condition I have would three excellent looking telescope that gave poor images. The 4" Celestar had a spherical primary that I fixed, the 6 Celestar lacked baffling so the image would always be washed out and the RV-4 had a defective drive and a  bad secondary, along with the  secondary mount being  made wrong. 

   If the goal is to use a classic scope then as you point out you keep what was right and fix what was wrong.

 

                        - Dave 


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#56 Chuck Hards

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Posted 12 August 2019 - 12:43 PM

I get this, Dave.  Read my post, I'm advocating what you do.  If it doesn't work, it doesn't matter what it looks like.  I'm wondering why it's even discussed.  Anyone not advocating the optics functioning well shouldn't be in this hobby.


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#57 Mark F

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Posted 12 August 2019 - 12:58 PM

Beautiful work and scope, I wish I had the talent.



#58 tim53

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Posted 12 August 2019 - 02:18 PM

 I watch over a Porter Garden Telescope and have tested the optics. They are very good but I would have no issue in making a new primary to replace the one that is in it so the scope would be usable or more usable in it present state. Porter design the scope to be used as a telescope to view the Universe. It does no good in my book not to have it work the they is was design

   At Mt Cuba Observatory we have 4" Clark and we use for public nights. The lens had issue and we had it refigured by D&G. Now the public see the views the way Clark meant them to be and we are turning people onto astronomy not off. 

   If your into car restoration you know that you want the car to restored so it runs like it was designed and not so much like it was built because many times there were mistakes. It wasn't meant to be that way so again there is no sin in my book to make it right.

 

                       - Dave 

True.  In my case, i have a '29 Model A Fordor that I need to finish the restoration on.  From experience with the panel truck, which is all original except for the Mitchell overdrive (so it'll go 60, though it's kind of exciting above about 50-55), I have no problem making some bolt-on modifications to make the car more reliable and safe to drive in the 21st century.  Things like upgrading the 4-banger to 64 hp with a counterweighted crank and lightened flywheel, Mitchell overdrive (and swapping the 4.11:1 ring and pinion for a 3.78:1.  I haven't done it yet, but I'll probably put juice brakes on it and electronic ignition and a 6 or 12-volt alternator.  All reversible.

 

For my scopes, the modern commercial ones don't bother me to refigure the optics for.  Like the MK63 with the bad primary.  You're helping me make it better than new (though I had to make it a lot worse to start! such is trial and error!).  On the other end of the spectrum are the Watkins and Smith Gregorian.  The original secondary is missing, so I'll have to get lucky and find one or just make one.  It would be nice to see the scope functional.  I would be sure to document anything I did, so it could be separated from the original in 1000 years if someone is interested in it.  The primary is pretty good, with a turned edge.  I don't plan to do anything to it.

 

-Tim.



#59 dan boyar

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Posted 13 August 2019 - 12:33 AM

Dave:

These have an undersized tube and imaging problems occur due to tube currents.  If you point the scope nearly overhead the effect normalizes after a short while and images will be perfect. If you then move the scope to say 45 degrees and observe say a bright star you will see tube current begin to distort the image.  Using the scope on a breezy night helps minimize the problem.  I have (3) 4" Dynascopes and know them well.  Optics are great on them!  Regards,  Dan B., FL



#60 DAVIDG

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Posted 13 August 2019 - 09:22 AM

Dave:

These have an undersized tube and imaging problems occur due to tube currents.  If you point the scope nearly overhead the effect normalizes after a short while and images will be perfect. If you then move the scope to say 45 degrees and observe say a bright star you will see tube current begin to distort the image.  Using the scope on a breezy night helps minimize the problem.  I have (3) 4" Dynascopes and know them well.  Optics are great on them!  Regards,  Dan B., FL

 Dan,

   I haven't seen that as a problem. If you have haven't fixed the problem with the secondary stalk not being the correct length to position the secondary correctly you'll never get an image  quality that they are capable  of  since it makes  the scope look collimated but the primary is tilted which is introducing astigmatism into the image 

 

We had excellent images when I had the scope up at Stellafane last weekend. Just perfect Airy disks no matter were the scope was pointed and had no issues splitting tight   doubles. The tube is sealed in the back around the  mirror cell which causes the air in the tube not to mix. The result is less tube currents not more. When the back is open around the mirror you have the  classic "chimney effect" with air being pulled in from the bottom and out the top of  the tube causing constant tube currents. I build all my scope with sealed backs to deaden the air movement in the tube.

   If you have every made and tested optics you see the effect of air movement when you test so you test in a tunnel or in an area with no air movements to get a clear view the surface of the optics. I do the with my design of telescopes as well. The result has been sharper images. 

 

                      - Dave 



#61 Tim Hager

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Posted 14 August 2019 - 08:40 AM

Dave,

One of these little scopes was given to me for Christmas 1966 as my first telescope.  I was too young then to tell whether the optics were good or bad but I enjoyed it tremendously.  I eventually gave it to my oldest son and the scope has since disappeared.  

 

For nostalgia, I bought another one a few years ago and these threads have inspired me to make the modifications to it to bring it back to top performance.  I may even make a Delmarva mount for it.  

 

Thanks for taking the time to walk us in detail through this and all of your restorations.

 

Tim


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