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Sears(Towa) #4-6340 Enhancements & Upgrades

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#1 Sky Muse

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Posted 10 October 2018 - 04:04 PM

specs-label2.jpg

 

When it first arrived, about two years ago, the doublet, straight up and out of its cell, was shuffled, with the flint on top.  But before I had realised that, I made an effort to mark the edges of the doublet nonetheless; little did I know at the time, and in vain as it turned out....

 

objective7b.jpg

 

Last night, I put the doublet in order, with the plano surface of the flint facing downward, and one of the convex surfaces facing upward.  I then took the achromat out, to the edge the south slope, and aimed the wee eye at Saturn, at 35x with my modern Antares .965" 17mm Plossl.  Hmm, dim of course, but not bad, yet too far away to discern just how sharp it was, so whilst I was sitting there, I flipped the crown, and the view was worse.  That's all I really wanted to test.  I couldn't even bring it to focus.  I now know the proper order of the elements.  I left the crown flipped like that overnight, then just a bit ago I flipped it back, the order now correct, and just as I had had it before I even took it outside, by happenstance.  I then cleaned the edges and surfaces of the elements in preparation for blackening...

 

blackening.jpg

 

Once that was done, I marked the crown...

 

crown mark.jpg

 

Now, to remove what crud that may still be present on the surfaces of the lenses...


Edited by Sky Muse, 10 October 2018 - 04:08 PM.

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#2 Steve Allison

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Posted 10 October 2018 - 04:13 PM

If the plano surface of the flint element is facing downward, its concave surface will be facing up. This concavity matches the convexity of the crown lens. I guess I am not clear about what you are trying to say...

 

Steve

 

Last night, I put the doublet in order, with the plano surface of the flint facing downward, and one of the convex surfaces facing upward. 


Edited by Steve Allison, 10 October 2018 - 05:39 PM.

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#3 Steve Allison

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Posted 10 October 2018 - 05:44 PM

I guess you were referring to one of the convex surfaces of the crown element facing up as its other convex surface rested on the concave flint element. At my age, confusion is a way of life. frown.gif

 

Steve



#4 Sky Muse

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Posted 10 October 2018 - 05:52 PM

In the case of longer achromats, it's more difficult to tell which convex surface faces the concave surface of the flint, and which faces the sky.  The curves on either side are not steep enough to differentiate.  You then take it outside and view an object, a detailed object, like Saturn, with both convex surfaces of the crown, flipping it once in the process.  Whichever side gives the best view, you've hit the jackpot.  It's quite simple, really.


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#5 Steve Allison

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Posted 10 October 2018 - 05:54 PM

Got it.


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#6 Sky Muse

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Posted 10 October 2018 - 06:59 PM

I had blackened the doublet's retaining-ring two years ago, but not the cell itself...

 

blackening3.jpg

 

My camera can't focus too well when the object is deader than a door-nail.

 

blackening2.jpg

 

The aperture is not very large, and when compared to a penny...

 

blackening4.jpg

 

...but if I was only twelve inches tall, the aperture of this li'l beauty would be a whopping 10" to 12" in diameter, therefore no aperture-fever here.


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#7 Sky Muse

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Posted 10 October 2018 - 08:04 PM

The interior of the dew-shield has been satinised...

 

flocking.jpg


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#8 Sky Muse

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Posted 10 October 2018 - 11:40 PM

The dew-shield is now flocked, and shown here with the blackened cell and retaining-ring...

 

flocking2.jpg


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#9 Steve Allison

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Posted 11 October 2018 - 12:03 AM

It's fun to see your efforts to get that last scintilla of performance out of your telescopes! 


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#10 Sky Muse

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Posted 11 October 2018 - 12:26 AM

It's fun to see your efforts to get that last scintilla of performance out of your telescopes! 

Yeah, and it's going to need it, too, as there was some haze on the flint element that I had to remove, and with its removal, gone the tired ol' MgF2 coating below it.  That side of the flint had been exposed all these decades past.  Either the original owner flipped the doublet when it was relatively new, or it had arrived from the factory flipped.


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#11 tony_spina

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Posted 11 October 2018 - 10:00 AM

Looking good Alan


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#12 Sky Muse

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Posted 11 October 2018 - 02:55 PM

Very early this morning, and not long before retiring, I snuck into the kitchen, and lo and behold, I found two woefully out-of-date(8 years+) McCormick® plastic spice containers...

 

stands.jpg

 

...thyme leaves, and dill weed, and both at least half-full...

 

stands2.jpg

 

stands3.jpg

 

objectivity.jpg

 

That flint element, at right, however, will be getting one more buffing-out before the painting begins.


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#13 Sky Muse

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Posted 11 October 2018 - 07:37 PM

The flint element had borne the brunt of the mishandling of the doublet over the decades.  Clamshells...

 

clamshells.jpg

 

The one protruding slightly into the surface(top) might just be concealed once the spacer and retaining-ring are in place.  The one on the side(bottom) protrudes very slightly into the interior of the lens.

 

Inconsequential, at first thought, but should the damage be arrested?  Would filling them in with clear epoxy be of help?


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#14 tony_spina

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Posted 11 October 2018 - 10:55 PM

The flint element had borne the brunt of the mishandling of the doublet over the decades.  Clamshells...

 

attachicon.gif clamshells.jpg

 

The one protruding slightly into the surface(top) might just be concealed once the spacer and retaining-ring are in place.  The one on the side(bottom) protrudes very slightly into the interior of the lens.

 

Inconsequential, at first thought, but should the damage be arrested?  Would filling them in with clear epoxy be of help?

Good question about filling in the chips in the lenses.  I would be interested in finding out what the experts on the forum advise 


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#15 shredder1656

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Posted 12 October 2018 - 05:22 AM

Very cool step-by-step.  Awesome care and effort.  Nice job!

 

Regarding the chips, I am no expert, so remember that.  However, I would think that blackening any chipped areas would be more beneficial than filling with something clear.  In my mind (again, that is a very solid and nearly impenetrable area) anything done to a chipped area on the lens is to prevent the light from traveling through that spot at all.  


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#16 Garyth64

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Posted 12 October 2018 - 12:30 PM

"Would filling them in with clear epoxy be of help?"

 

No, I am sure that it won't.


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#17 Sky Muse

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Posted 12 October 2018 - 02:38 PM

Good question about filling in the chips in the lenses.  I would be interested in finding out what the experts on the forum advise 

I had already scoured the internet and read about using black paint, the ultra-flat that I have for example.  I ran across this...

 

https://www.instruct...lement-of-a-Le/

 

...not quite analogous, however it could be a solution for the scratched-up crown of my very first telescope, and achromat.

 

Incidentally, the surprise arrives today, and the package weighs less than a single pound.


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#18 tony_spina

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Posted 12 October 2018 - 06:09 PM

I had already scoured the internet and read about using black paint, the ultra-flat that I have for example.  I ran across this...

 

https://www.instruct...lement-of-a-Le/

 

...not quite analogous, however it could be a solution for the scratched-up crown of my very first telescope, and achromat.

 

Incidentally, the surprise arrives today, and the package weighs less than a single pound.

Looking forward to seeing pictures of the surprise grin.gif


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#19 tony_spina

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Posted 12 October 2018 - 06:11 PM

Forgot to ask, in regards to the lens edge blackening are you using paint or a sharpie? 



#20 Sky Muse

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Posted 12 October 2018 - 06:43 PM

Forgot to ask, in regards to the lens edge blackening are you using paint or a sharpie? 

This...

 

ultra-flat.jpg

 

...and flocking, only.  I've never used a marker, and never will.



#21 Sky Muse

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Posted 12 October 2018 - 06:52 PM

The surprise...

 

mounting solution.jpg

 

I had forgotten that the anodised-orange bar was already spoken for, and for the Celestron 70mm f/13 achromat...

 

4.jpg

 

But I did have the Meade-blue one, and from the Meade 90mm f/10 achromat...

 

kit.jpg

 

All's well that ends well.

 

The copper-plated "malleable"-iron rings are slightly chunky for the scale of this 50mm, specifically where the clamps close, but overall diminutive nonetheless.



#22 tony_spina

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Posted 12 October 2018 - 08:29 PM

Will be interested in seeing those clamps on the scope to get a sense of size


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#23 Sky Muse

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Posted 12 October 2018 - 08:44 PM

Will be interested in seeing those clamps on the scope to get a sense of size

I've already test-fitted them.  They will need a layer of thick felt at least, but once you do see them, you'll place that order. 



#24 Sky Muse

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Posted 12 October 2018 - 09:06 PM

I had shaved a very-fine point onto the tip of a toothpick, and filled in the two areas in question with epoxy.  I used a cheap pair of reading-glasses whilst filling them in, from Dollar Tree if I remember correctly.  Now, I don't need said glasses for reading.  For me, they act as a magnifier, and where I can draw up to about 6" away with my eyes, and it's clear as a bell.  No, no glue migrated onto the intact surface; only within the depressions.  I was very careful not to overfill the one at the surface, and so to rise above same.  The other did not matter, as it's on the side.  Nonetheless, after the glue had cured I ground each down with a diamond-file, then #0000 steel-wool.  Instead of "stoning", or frosting, the glass itself, the epoxy was "stoned" instead...

 

clamshells2.jpg

 

clamshells3.jpg

 

Still, I may blacken the one at the surface, but the other will be blackened automatically as I go round with the ultra-flat black paint, and with a brush.

 

A overhead shot of the repaired flint element...

 

flint repair2.jpg

 

Again, I'm thinking that the spacer combined with the retaining-ring will render the visible damage...invisible.  We'll see.


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#25 tony_spina

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Posted 12 October 2018 - 10:32 PM

I've already test-fitted them.  They will need a layer of thick felt at least, but once you do see them, you'll place that order. 

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