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Intes MK63. I don't NEED another scope!

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#76 tim53

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Posted 13 October 2019 - 04:18 PM

I'm back to work on fixing this mirror today.  Been quite a while, but not as long as my last post about it.  Reason being, I made the figure a lot worse before I started making it better.  I can claim it's "part of the plan" so I can gain experience before tackling the C-14 or the Mak 16".

 

-tim.



#77 tim53

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Posted 01 December 2019 - 04:48 PM

Almost there. I have a sphere with a bit of a tde and a hill around the perforation. Worse, my sphere is rough. So today I’m softening my pitch with some olive oil. 
 

 

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#78 tim53

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Posted 01 December 2019 - 08:27 PM

Well phooey.  I spent most of the afternoon trying to whip the lap into shape.  These fast mirrors are a pain to press, IMHO, because the pitch wants to form a level surface in the toaster oven, but the mirror needs it to be mounded up in the center.  I got almost there, but with a low spot off center (wish it were on-center where the hole in the mirror lives), when I just had to put it away for the day.  Don't know when I'll get back to it now. 

 

-Tim.


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#79 G-Tower

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Posted 01 December 2019 - 11:33 PM

Have you tried the Emeril pitch lap maker?


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#80 tim53

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Posted 01 December 2019 - 11:54 PM

Have you tried the Emeril pitch lap maker?

Mine's more better, because it was free!  wink.gif


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#81 Terra Nova

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Posted 02 December 2019 - 10:15 AM

Mine's more better, because it was free!  wink.gif

It’s hard to beat FREE! 



#82 tim53

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Posted 20 March 2020 - 11:08 AM

So I have been slowly working on this refigure for several months of acopious spare time now.  My pitch lap has been on a 3/4" plywood disk, shellacked (so-so sealed).  Hot pressing was always a challenge the several times I've re-formed the lap, because of the steep curve of the primary mirror.  I can quickly get it pressed to about halfway to the center of the mirror, then it's cooled enough that going any further takes lots of time, weight, and repeated tweaks with a heat gun.  And still I never got it pressed quite to the perforation.  

 

Then, even using typical strokes to spherize, I keep getting a TDE and hill around the perforation.  Even thinning the pitch to soften it didn't seem to help any.

 

So now, I ordered some dental stone and poured a new tool that has the primary's shape and perforation.  So when I pour and press the new lap, it should have a uniform thickness throughout.  And hopefully getting to a perfect sphere will be straightforward!  

 

Family portrait:

 

Mirror_newtool.jpg



#83 G-Tower

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Posted 20 March 2020 - 03:26 PM

The problem may be your stroke and pressure.



#84 tim53

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Posted 21 March 2020 - 10:12 AM

Perhaps.  I've tried pretty much everything I could think of.  But the lap on the plywood disk is about twice as thick in the center as at the edge, and has to be affecting the way the pitch adjusts to the figure.

 

In any case, I still have the lap and could go back to it if necessary.

 

-Tim.



#85 Augustus

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Posted 21 March 2020 - 04:28 PM

I would plug the hole in the primary with hard pitch, personally. 



#86 davidc135

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Posted 21 March 2020 - 05:00 PM

Very likely a stupid idea but could wrapping a tube packed with salt or calcium chloride/ice around the edge during polishing help with the tde? Just a remote chance. Ensuring an even thickness of pitch sounds right.  David


Edited by davidc135, 21 March 2020 - 05:00 PM.

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#87 tim53

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Posted Today, 03:15 PM

Made a new lap yesterday, but only just started using it.  Still some pressing to do. It's amazing how hard it is to squeeze down the outer edges with a fast mirror.  makes me wish I'd been paying attention when Gerry Logan described how he pours pitch on a surface (wax paper?) and transfers it to the tool before it's too hard.  With terpentine on the tool to help it stick.  That would give a uniform thickness of pitch draped over the tool.  But I couldn't figure out how to make the dam to contain the pitch that way.

 

-Tim.



#88 davidc135

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Posted Today, 04:32 PM

Could plywood be used for the dam? If it's finished smooth and coated with cerox.Could be made in two halves which pull apart.  David




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