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Let the antique speak for itself...

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#51 terraclarke

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Posted 12 January 2019 - 10:59 AM

The key test was on the objective. Although it is in need of a thorough cleaning, a view of distant tree branches was sharp and clear:

attachicon.gif 20190105_124755 (2).jpg

Rough measurement when in focus(from the objective to the eyepiece) was 96"...so this is an f/16 instrument.

Star test on Capella and its star field later in the evening showed sharp pinpoints and no chromatic aberration.

John

Sure looks like a lot of purple in this picture for “no chromatic aberration”.


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#52 John Higbee

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Posted 12 January 2019 - 11:00 AM

and for those who like dents:

dents 1.jpg

dents 2.jpg
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#53 John Higbee

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Posted 12 January 2019 - 11:08 AM

and more dents:

dents 3.jpg

dents 4.jpg

One of my near-term projects is to create an "OTA map" charting all the dents I will have to address during OTA refurb...just so I don't miss any!
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#54 John Higbee

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Posted 12 January 2019 - 11:15 AM

Also - I intend to implement Bremms recommendation on additional OTA baffles. I could use your collective help on two items:

How should I calculate proper baffle locations and apertures within the OTA for a four baffle system in this OTA?

How should the baffles be attached to the OTA (for the two existing ones, no fasteners were used...looks like material was "built up" on the OTA on both sides of the baffle to hold it in place).

#55 John Higbee

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Posted 12 January 2019 - 11:33 AM

Sure looks like a lot of purple in this picture for “no chromatic aberration”.


Terra - You're right! Dave and I didn't see it when we were looking through the telescope...but the handheld picture (using a Galaxy smartphone) sure seems to shows it.

Observation conditions (which may not affect CA):
Collimation status of the objective is unknown
Background was extremely bright (thin stratus clouds)
Makeshift drawtube had significant lateral play in the focuser tube (i.e. it drooped)

I didn't see any CA around Capella later that evening, but it might have been there (combination of a cold night and wanting to get the OTA back indoors while I had help resulted in a brief look).

If there is CA after we finish the renovation, I'll accept that as a fact and be happy we've preserved a unique piece of history. I look forward to your help and advice as we "start this trek"!

thanks, John

Edited by John Higbee, 12 January 2019 - 11:34 AM.

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#56 combatdad

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Posted 12 January 2019 - 11:56 AM

To add to John's comments concerning CA, I spent a good amount of time at the eyepiece while aligning the viewfinder...looking at lots of branches...and was looking for any false color.  My first comment to John when seeing his photo was..."where did all the purple come from?!" 

 

As John said we will know better with an aligned focuser...and a good star test.  Regardless, it's going to be fun playing with that puppy smile.gif

 

Dave


Edited by combatdad, 12 January 2019 - 11:57 AM.

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#57 apfever

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Posted 12 January 2019 - 11:56 AM

Would the near focus of branches, compared to the infinity focus of a sky object, affect the amount of CA?


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#58 Dan /schechter

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Posted 12 January 2019 - 01:04 PM

Next picture - the mount and tripod with my friend combatdad.

attachicon.gif Dave after mount assembly.jpg

John

Hi John,

Congratulations!!!   I have had a chance to view through two Clint Whitman's 4" Saturns and they both were outstanding. One evening we placed one side by side with my 4" "Whitman" Clark and they were equal. The Tinsley had just a hair better contrast since it's optics were coated. If yours is optically equal, you will fall more in love with it. Great f/16 optics are wonderful to use on planets, the moon double stars and other objects.

 

I also noticed the elevating apparatus on your mount. I own a Zeiss that fits on an alt/az stand with a elevating post that is strong enough (just like Zeiss usually makes) to lift a car. I find it amazing that it very accurate in maintaining an object in the observing field as the operator raises and lowers it. Please describe how well your mount works when you get a chance to evaluate it.

 

I noticed in your opening post that you obtained this Tinsley from your local Astronomy club. Have you been able to get any information on its provenance? Tracing down that information can be as much fun as using the scope, especially on a "Cloudy Night".

 

Looking forward to hearing more about your Tinsley and again, congratulations!!!

 

Dan


Edited by Dan /schechter, 12 January 2019 - 01:06 PM.

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#59 Kasmos

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Posted 12 January 2019 - 03:18 PM

I noticed the purple but didn't speak up. There's faint yellow on the opposite sides of the branches too, so I wondered about the color free statement. That said, hopefully it's from the phone camera as digital cameras can tend to add purple on bright images.


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#60 John Higbee

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Posted 12 January 2019 - 06:23 PM

Hi John,
Congratulations!!!   I have had a chance to view through two Clint Whitman's 4" Saturns and they both were outstanding. One evening we placed one side by side with my 4" "Whitman" Clark and they were equal. The Tinsley had just a hair better contrast since it's optics were coated. If yours is optically equal, you will fall more in love with it. Great f/16 optics are wonderful to use on planets, the moon double stars and other objects.
 
I also noticed the elevating apparatus on your mount. I own a Zeiss that fits on an alt/az stand with a elevating post that is strong enough (just like Zeiss usually makes) to lift a car. I find it amazing that it very accurate in maintaining an object in the observing field as the operator raises and lowers it. Please describe how well your mount works when you get a chance to evaluate it.
 
I noticed in your opening post that you obtained this Tinsley from your local Astronomy club. Have you been able to get any information on its provenance? Tracing down that information can be as much fun as using the scope, especially on a "Cloudy Night".
 
Looking forward to hearing more about your Tinsley and again, congratulations!!!
 
Dan


Dan - thanks! The elevating apparatus is a brass column about 30" long. The handwheel rotates very smoothly (4-5 turns per inch of travel). When I observed Capella, the pier was raised about 15" -- the mount was rock solid.
As far as provenance is concerned, I know that Clint Whitman (when he got the Saturn manufacture numbers) was told by Tinsley that only 3 6" refractors were manufactured. Beyond that, the rest of the scope's history remains to be determined.
John

Edited by John Higbee, 12 January 2019 - 06:23 PM.

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#61 Dan /schechter

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Posted 13 January 2019 - 02:45 AM

Dan - thanks! The elevating apparatus is a brass column about 30" long. The handwheel rotates very smoothly (4-5 turns per inch of travel). When I observed Capella, the pier was raised about 15" -- the mount was rock solid.
As far as provenance is concerned, I know that Clint Whitman (when he got the Saturn manufacture numbers) was told by Tinsley that only 3 6" refractors were manufactured. Beyond that, the rest of the scope's history remains to be determined.
John

Hi John,

I am not surprised the mount is rock solid. Maybe you can get in touch with Clint and he can tell yo how to get in touch with the employee at the Tinsley Corp. Hopefully they have records of where and when the 3 6" refractors were manufactured and who purchased them. Doe your Astronomy club know how and from whom they acquired the telescope?

 

Good luck with your search,

Dan


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#62 bremms

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Posted 13 January 2019 - 09:39 AM

I noticed the purple but didn't speak up. There's faint yellow on the opposite sides of the branches too, so I wondered about the color free statement. That said, hopefully it's from the phone camera as digital cameras can tend to add purple on bright images.

No matter how good, a standard 6" F15 achromat will still show a lot of secondary spectrum. Next to a reflector it will be extremely obvious.

I have a 6" F10 Jaegers and had a 6" f15 Jaegers. The F15 has less color. I currently have an Istar 6" f15 that looks like it has a bit less secondary spectrum than the Jaegers f15. Could be glass they use.


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#63 bremms

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Posted 13 January 2019 - 09:54 AM

Hi John,

I am not surprised the mount is rock solid. Maybe you can get in touch with Clint and he can tell yo how to get in touch with the employee at the Tinsley Corp. Hopefully they have records of where and when the 3 6" refractors were manufactured and who purchased them. Doe your Astronomy club know how and from whom they acquired the telescope?

 

Good luck with your search,

Dan

I think that is a great idea. This is the kind of scope that may have an interesting history. One of the reasons I like the Tinsleys, Fekers, B&L and similar. They made in small numbers and are very unique.


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#64 starman876

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Posted 13 January 2019 - 09:54 AM

Thanks, Johann - you're welcome to come over the next time Dave and I get together! John

Thanks for the invite.  Please let me know when that happens.


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#65 DAVIDG

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Posted 13 January 2019 - 11:55 AM

 I can't stress enough to get the lens up on ther test bench and test it by Double pass autocollimation. I have worked on many classic and vintage objectives like  Clarks and Brashears and it is Very common to have  an element flipped or the lens totally backwards in the cell. Do not believe any alignment marks you find. Over the years that lens could have disassembled  many times and by people  that did not really understand what was going on so their  marks can be wrong and misleading. Again I have seen it many times. Also don't assume it is a crown forward design. The 10" Hartness House Turret scope when restored in the 70's was found to have been cemented and installed in the cell backwards for at least 30 to 50 years. It is an air spaced Flint forward design and not a classic crown forward one.

    I also can't stress enough that a flipped element or even having the lens backwards in the cell will not give a total mess of an  image that won't come to focus, in many cases like the Hartness scope the images wasn't bad  but no where  near as good as it is now when correctly assembled.  So getting an image that looks "Ok" is not proof that the lens is assembled correctly. 

   The fact that your getting a far amount of chromatic aberration is pointing to a possible problem so again don't assuming anything. Testing on the bench will tell you in 2 minutes what is going on and if you flip element or reverse the objective it will tell you with  confidence if you made an improvement or not vs guessing if it is  the seeing or eyepiece etc. Good luck.

 

               - Dave 


Edited by DAVIDG, 14 January 2019 - 09:56 AM.

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#66 Darren Drake

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Posted 13 January 2019 - 12:15 PM

If the elements were flipped I believe the images would be much worse than seen here.  The CA shown in the pic is normal this type of achromat.  If the star test is reasonably good then then that indicates all is well..


Edited by Darren Drake, 13 January 2019 - 12:16 PM.

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#67 starman876

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Posted 13 January 2019 - 12:40 PM

I can test the lens for you John if you have any doubts.



#68 John Higbee

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Posted 13 January 2019 - 02:51 PM

I can't stress enough to get the lens up on ther test bench and test it by Double pass autocollimation. I have worked on many classic and vintage objectives like  Clarks and Brashears and it is Very common to have  an element flipped or the lens totally backwards in the cell. Do not believe any alignment marks you find. Over the years that lens could have disassembled  many times and by people  that did not really understand what was going on so their  marks can be wrong and misleading. Again I have seen it many times. Also don't assume it is a crown forward design. The 10" Hartness House Turret scope when restored in the 70's was found to have been cemented and installed in the cell backwards for at least 30 to 50 years. It is an air spaced Flint forward design and not a classic crown forward one.
    I also can't stress enough that a flipped element or even having the lens backwards in the cell will not give a total mess of an  image that won't come to focus, in many cases like the Hartness scope the images wasn't bad  but no ever near as good has it is now when correctly assembled.  So getting an image that looks "Ok" is not proof that the lens is assembled correctly. 
   The fact that your getting a far amount of chromatic aberration is pointing to a possible problem so again don't assuming anything. Testing on the bench will tell you in 2 minutes what is going on and if you flip element or reverse the objective it will tell you with  confidence if you made an improvement or not vs guessing if it is  the seeing or eyepiece etc. Good luck.
 
               - Dave

Dave - thanks so much for your advice. I will definitely have the objective DPAC tested. Given the age and the condition of the telescope, I'm approaching each step of the refurbishment as a "prove, don't assume" evolution.

John
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#69 John Higbee

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Posted 13 January 2019 - 02:53 PM

I can test the lens for you John if you have any doubts.

Thanks, Johann - I will probably take you up on your offer! John
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#70 terraclarke

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Posted 13 January 2019 - 04:54 PM

I’d love to know how it compares optically with your rare 6” Spacek refractor.


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#71 DAVIDG

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Posted 13 January 2019 - 06:11 PM

Thanks, Johann - I will probably take you up on your offer! John

 John,

    With all the work your going to put into the restoration, you'll have  piece of mind knowing there is no issues with the lens if you have it tested. It won't take no more than 15 minutes and if you do see a problem simply turning it around  on the test stand will tell you if lens is  backwards in the cell.   If it tests worse then the initial results then that is not the problem. Then try flipping the front element  Hopefully it will test well from the start and you won't have to do anything 

 

                   - Dave  


Edited by DAVIDG, 13 January 2019 - 06:37 PM.

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#72 John Higbee

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Posted 13 January 2019 - 06:43 PM

I’d love to know how it compares optically with your rare 6” Spacek refractor.

After the restoration is complete, this will be done, and the results posted!



john and 6 inch at NEAF (1).jpg

6 inch in full operation.jpg

Edited by John Higbee, 13 January 2019 - 06:49 PM.

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#73 AstroKerr

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Posted 13 January 2019 - 07:01 PM

That slight purple CA is 'tree glow' (known by other names as well) and it's is a wonderful example of an 'selective objective' - one in which targets that are not among the objective's 'intended view catalog or realm' are highlighted by the objective's optics/coatings to alert the user he's viewing 'out of realm' or 'out of catalog'. I'd say that's a keeper.

 

Very nice acquisition, Johnathan =)


Edited by AstroKerr, 13 January 2019 - 07:03 PM.

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#74 starman876

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Posted 13 January 2019 - 08:41 PM

Thanks, Johann - I will probably take you up on your offer! John

Just let me know when you want to do it.



#75 bremms

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Posted 13 January 2019 - 11:00 PM

 I can't stress enough to get the lens up on ther test bench and test it by Double pass autocollimation. I have worked on many classic and vintage objectives like  Clarks and Brashears and it is Very common to have  an element flipped or the lens totally backwards in the cell. Do not believe any alignment marks you find. Over the years that lens could have disassembled  many times and by people  that did not really understand what was going on so their  marks can be wrong and misleading. Again I have seen it many times. Also don't assume it is a crown forward design. The 10" Hartness House Turret scope when restored in the 70's was found to have been cemented and installed in the cell backwards for at least 30 to 50 years. It is an air spaced Flint forward design and not a classic crown forward one.

    I also can't stress enough that a flipped element or even having the lens backwards in the cell will not give a total mess of an  image that won't come to focus, in many cases like the Hartness scope the images wasn't bad  but no ever near as good has it is now when correctly assembled.  So getting an image that looks "Ok" is not proof that the lens is assembled correctly. 

   The fact that your getting a far amount of chromatic aberration is pointing to a possible problem so again don't assuming anything. Testing on the bench will tell you in 2 minutes what is going on and if you flip element or reverse the objective it will tell you with  confidence if you made an improvement or not vs guessing if it is  the seeing or eyepiece etc. Good luck.

 

               - Dave 

Dave is right. I had 3" Fecker refractor lens that was flipped. It had enough SA on a star test that I knew something was bad wrong instantly. Using a Ronchi test on a star showed the problem as well.  I looked at it and looked at it. It seemed right until I noticed the coating was on the inside element and was worn. Could it be a Steinheil?? Sure was, flipped it around and the lens test was very good. I was using a 133LPI grating on a star too. Didn't have a flat.  Recently picked up a 127 x1200mm Surplus Shed achromat. These are somewhat notorious for flipped elements. DPAC'd mine and it had scads of SA. DPAC looked like a watermelon. Sure enough the crown element was flipped. The Surplus Shed lens is very good after proper assembly. DPAC was VERY good. Shockingly so. Maybe I was lucky, but others have had a good ones as well.


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