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Let the antique speak for itself...

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#126 deepwoods1

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Posted 03 September 2019 - 07:14 PM

Exciting indeed!


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#127 John Higbee

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Posted 11 September 2019 - 02:52 AM

I have also been working with the ATS folks on their website.  One of them provided me a picture of a Tinsley cassegrain with the OTA painted the same "medium green" as my original paint (as protected by the OTA rings).  So, there Is a precedent for this color on Tinsley telescopes...a medium green with the slightest amount of "wrinkle" in it.

 

I am going to restore the original aluminum tube...but am seriously considering making a second OTA out of brass for actual observational work.  Brass is over twice as heavy as aluminum, thus should be able to withstand the rigors of travel, set up and disassembly better than the original.  The mount, pier and tripod are extremely robust and should have no problem handling the additional load. 


Edited by John Higbee, 11 September 2019 - 02:53 AM.

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#128 terraclarke

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Posted 11 September 2019 - 10:40 AM

I know a person who has a 6” F15  brass Carroll refractor. It’s the one Chesley Bonestell used to observe the moon with back around 1950 when he was doing the illustrations to be used by Walt Disney and George Pal in their films and the old (original) Disneyland amusement park ride-Flight to the Moon. Anyway, long story short (please forgive the pun), the brass tube is in two half-sections that couple together. It’s a very strong union that always preserves collimation yet it makes transport much easier. He takes it to the field frequently on fairly long trips in the back of his pickup, (or used to, I haven’t seen him or the scope in fifteen years, yet I hear that both are still doing well).


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#129 oldscope

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Posted 13 September 2019 - 07:26 PM

Johann and I had another session with the 6" objective yesterday, and made some significant progress in objective alignment and DPAC.

 

Last weekend, we had several unresolved problems at the end of the session:

  • Signficantly skewed Ronchi lines on the DPAC
  • Newton rings that were skewed away from the center of the objective
  • An objective that fit so tightly into the cell that there was no slight "rattle" heard after objective reassembly

David G. gave us some good advice on troubleshooting, which we followed yesterday:

  • Removing the cell from the objective, and checking the shims and air gap between the crown and flint
    • Shims were in good shape, and air gap was even around the objective perimeter
    • Using a template, found all three to be symmetrical (120 degrees apart, plus or minus a degree)
  • Checking the three support points at the bottom of the cell for proper placement
    • Using a template, found all three to be symmetrical (got similar spacing results as for the shims)

We also cleaned the inside of the cell: 

  • Removed a lot of dirty film from the inside cell walls 

When we re-assembled the objective, we ensured that the objective shims and the lower support points were aligned.  The objective went in on the first try with no difficulty.  We also ensured that the objective retaining ring was installed "hand-tight, then backed off slightly"...and we did get the "slight rattle" that had been missing previously.

 

Newton rings were symmetric and centered...and we had three straight lines on the DPAC testing!  (...and there was great rejoicing! grin.gif ).  It's possible that one element may have very slightly cocked in the cell during last week's activities, due to the dirty residue on the cell walls...that, and/or the misalignment of the objective shims to the cell support points, may have been the cause of last week's problems.

 

As a final (unrelated) step, we cleaned and tested the 3" f/6 objective for the finder on the 6" Spacek.  I had not been able to disassemble the finder previously, but with Johann's help we got it apart, and found that one of the objective shims was out of the air gap entirely (was on the edge of the objective...we reinstalled it after cleaning both elements).  During reassembly, Johann demonstrated for me what DPAC results for a reversed objective and flipped element looked like...as Dave G. says, DPAC will immediately show you those conditions if they exist!  Finder is reassembled, shows fine images, and is reinstalled on the 6" OTA.

 

All in all, a great day!  Many thanks to Johann, for his support and his patience teaching a refractor "newbie" about optical maintenance and testing!

 

John   

John,

 

Some years (decades?) ago, I had a conversation with Barry Greiner, the 'G' of D & G Optical. He mentioned that retaining rings should not really allow the glass to rattle. Of course, neither should they be applying undue pressure. But they need to keep the elements from moving freely. At most, you want to hear an almost imperceptible clicking ... you should have to shake the cell and barely hear it. If the sound is obvious and easy to hear, your ring is a bit too loose. This is especially true if there are soft spacers such as paper or plastic. You definitely don't want any obvious rattle then.

 

Well, that's my 2 pence.

 

BR

 

Bart


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#130 John Higbee

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Posted 13 September 2019 - 08:12 PM

Bart - thanks for the advice (which I agree with).  The objective is at the "slight clicking" level you describe...rattle would be overstating its degree of motion in the cell.

 

Just finished stripping the OTA this afternoon.  will be stripping the focuser and the OTA rings tomorrow...leaving the worst for last...the 50# fork and "rising column" mechanism. shocked.gif

 

Still shooting for a slot at the ATS booth for the 2020 NEAF...John


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#131 John Higbee

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Posted 15 September 2019 - 10:04 AM

Here is the focuser before several hours of hand sanding:

 

20181226_153918.jpg

 

and after:

 

focuser.jpg

 

the focuser casting is beautiful (no flaws in the casting that I can see)

 

Almost want to seal it (after polishing it) and install it as is...but Saturn telescopes focusers were painted the tube color, and its tube (once "un-dented") will be painted...so this is only a temporary view.  In any case, it's nice to see how well it was made!

 

On to the OTA rings...

 

John


Edited by John Higbee, 15 September 2019 - 10:06 AM.

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#132 starman876

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Posted 15 September 2019 - 11:05 AM

a lot of hard work John.  You are doing a great Job.  I have been extremely busy these last couple of months otherwise I would be helping.

 

Johann



#133 oldscope

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Posted 29 September 2019 - 05:16 PM

Does the nameplate come off? You might find the original color underneath. Also, not too difficult to get the focuser draw tube replated..Whoever does the work can strip the old plating chemically, but don't let them polish the hell out of the tube before plating it. That should be done very gently on a lathe or you will get uneven polishing and a gimpy focuser.

 

Bart


Edited by oldscope, 29 September 2019 - 05:18 PM.

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#134 John Higbee

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Posted 01 October 2019 - 05:15 AM

Does the nameplate come off? You might find the original color underneath. Also, not too difficult to get the focuser draw tube replated..Whoever does the work can strip the old plating chemically, but don't let them polish the hell out of the tube before plating it. That should be done very gently on a lathe or you will get uneven polishing and a gimpy focuser.

 

Bart

Bart - I did find the original color (a medium green, non-gloss, with a very fine "wrinkle" texture) when I took the OTA rings off the tube.  There were also traces of it on the focuser casting.  I verified that Tinsley used this color (one of our ATS friends pointed me towards a picture of a Tinsley 12" Cassegrain with a green OTA).

On the other hand, the only other 6" Tinsley we know of has the classic Tinsley "blue/grey" gloss finish...which I like better than the green.  So, I could go either way...will probably stick with the green if I can find a match for it in an "over-the-counter" enamel color.

Replating the focuser tube will be a future project...right now, it is operating well, and getting the focuser knob off looks to be a challenge (looks like it is fastened to the shaft with a pin, not a screw).  Getting the OTA and the fork/rising pier assembly repainted, and final refinishing done on the maple tripod legs, are next on the agenda.


Edited by John Higbee, 01 October 2019 - 05:17 AM.

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#135 oldscope

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Posted 09 October 2019 - 06:48 PM

Bart - I did find the original color (a medium green, non-gloss, with a very fine "wrinkle" texture) when I took the OTA rings off the tube.  There were also traces of it on the focuser casting.  I verified that Tinsley used this color (one of our ATS friends pointed me towards a picture of a Tinsley 12" Cassegrain with a green OTA).

On the other hand, the only other 6" Tinsley we know of has the classic Tinsley "blue/grey" gloss finish...which I like better than the green.  So, I could go either way...will probably stick with the green if I can find a match for it in an "over-the-counter" enamel color.

Replating the focuser tube will be a future project...right now, it is operating well, and getting the focuser knob off looks to be a challenge (looks like it is fastened to the shaft with a pin, not a screw).  Getting the OTA and the fork/rising pier assembly repainted, and final refinishing done on the maple tripod legs, are next on the agenda.

The pin you mention might be a tapered pin, which is actually easy to remove. If it is, one side will be slightly smaller than the other. Of course, tap the smaller side and it should come out with little trouble.

 

B.



#136 Bomber Bob

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Posted 09 October 2019 - 07:53 PM

On the other hand, the only other 6" Tinsley we know of has the classic Tinsley "blue/grey" gloss finish...which I like better than the green.

 

Which 6" Tinsley are you referring to?   A refractor or a Cassegrain?  I have a 6" Tinsley Saturn Cass, but I've never heard mention of another one.  The original paint on mine was that unusual blue/gray (+ green?) gloss.

 

15CM-CC-P102CN - OTA Before Restoration.jpg


Edited by Bomber Bob, 09 October 2019 - 08:05 PM.


#137 John Higbee

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Posted 11 October 2019 - 12:58 PM

On the other hand, the only other 6" Tinsley we know of has the classic Tinsley "blue/grey" gloss finish...which I like better than the green.

 

Which 6" Tinsley are you referring to?   A refractor or a Cassegrain?  I have a 6" Tinsley Saturn Cass, but I've never heard mention of another one.  The original paint on mine was that unusual blue/gray (+ green?) gloss.

 

attachicon.gif 15CM-CC-P102CN - OTA Before Restoration.jpg

I'm referring to the 6" f/16 achromatic refractor I am refurbishing (picture below).  Tinsley records reviewed by Clint Whitman in 2010 indicated that only three of these were ever made.  I have one; a member of the Antique Telescopes Society (ATS) has another; location of the third is unknown.

 

My OTA and focuser were largely bare (no primer was used).  The traces of color coat left on mine were a "forest" green with a very fine wrinkle texture. The ATS member's scope has the more common Tinsley "gloss bluish gray".

 

dave and the Tinsley.jpg

 

John  


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#138 Bomber Bob

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Posted 11 October 2019 - 08:35 PM

Yeah, I thought you were probably referring to the refractors.  Is the paint (that's left!) on my Cass that blue/gray you mentioned?  It has an unusual sheen in the sunlight that I haven't seen on any other scope, and it has a hint of green in it to me.  Indoors, the blue dominates.

 

[I've been trying since I got it from Bob Midiri to determine if Tinsley ever made another of these 6" Casses, since they aren't in any of the catalogs I've seen.]

 

I've been following your restoration with great interest -- and admiration.  Talk about a Big Project!!  




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