Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Help mirror grinding question

  • Please log in to reply
166 replies to this topic

#151 pjmulka

pjmulka

    Viking 1

  • *****
  • topic starter
  • Posts: 996
  • Joined: 17 Sep 2015

Posted Yesterday, 11:38 AM

I haven't had the opportunity to mount my camera on the new XYZ stage yet but here are some hand held shots.

 

Attached Thumbnails

  • Foucault1-(1).jpg
  • Foucault2-(2).jpg
  • Inside1-(1).jpg
  • Inside2-(3).jpg
  • Outside1-(1).jpg
  • Outside2-(2).jpg


#152 Pinbout

Pinbout

    ISS

  • *****
  • Posts: 26,490
  • Joined: 22 Feb 2010

Posted Yesterday, 12:48 PM

ok center looks cool [a little rough but figure 8's would get rid of that]

 

its the kink

 

now this is where you do the ToT edge from just inside the ink to outside the kink turning backwards, not all the way to the edge.

 

only 20mins and test.

 

all you need to do and look at is outside RoC.  outside RoC and hill is a hill and a hole is a hole.

 

you have a turned up edge now.


Edited by Pinbout, Yesterday, 12:50 PM.


#153 pjmulka

pjmulka

    Viking 1

  • *****
  • topic starter
  • Posts: 996
  • Joined: 17 Sep 2015

Posted Yesterday, 01:20 PM

So I’m only working a zone from like 70% to 85%?
  • Pinbout likes this

#154 pjmulka

pjmulka

    Viking 1

  • *****
  • topic starter
  • Posts: 996
  • Joined: 17 Sep 2015

Posted Yesterday, 01:22 PM

Here are some photos of the tester upgrades I’ve been working on while I’m lying on the couch. 
 

Attached Thumbnails

  • 70B27EED-F4D3-4D0D-B8B1-2171FABA3AA5.jpeg
  • D9EAD923-F158-40DF-963C-D67781FC2065.jpeg
  • 41C4D61B-A1D5-4C32-AE58-8C1E363D5096.jpeg
  • 4546CE3A-AAE5-409D-8219-078E4ED76829.jpeg


#155 dogbiscuit

dogbiscuit

    Surveyor 1

  • *****
  • Posts: 1,943
  • Joined: 18 Oct 2018
  • Loc: Barksdale

Posted Yesterday, 05:19 PM

I'm guessing that last work session was with the center of the lap depressed out of contact?



#156 Pinbout

Pinbout

    ISS

  • *****
  • Posts: 26,490
  • Joined: 22 Feb 2010

Posted Yesterday, 05:41 PM

I'm guessing that last work session was with the center of the lap depressed out of contact?

he keeps working those outer edges too much and doesn't know when to stop. ha ha ha



#157 dogbiscuit

dogbiscuit

    Surveyor 1

  • *****
  • Posts: 1,943
  • Joined: 18 Oct 2018
  • Loc: Barksdale

Posted Yesterday, 07:11 PM

he keeps working those outer edges too much and doesn't know when to stop. ha ha ha

I was just wondering how he got that shape, if it was pressing a star in the center of the lap.

 

Looks like only from about 70% zone to edge got any work. Reduced correction there but steep jump between that zone and the central area.  Not necessarily a bad result. Just need to extend the reduction of correction farther inward.  Maybe with a smaller depressed central area in the lap?
 



#158 pjmulka

pjmulka

    Viking 1

  • *****
  • topic starter
  • Posts: 996
  • Joined: 17 Sep 2015

Posted Yesterday, 07:32 PM

Yes the last work was done with a star pressed in the center of the lap. I’m a little confused about exactly how to do the stroke Danny suggested. I’m going to take some photos of what I think he’s saying and post to confirm before I do any more work.

#159 dogbiscuit

dogbiscuit

    Surveyor 1

  • *****
  • Posts: 1,943
  • Joined: 18 Oct 2018
  • Loc: Barksdale

Posted Yesterday, 08:05 PM

he keeps working those outer edges too much and doesn't know when to stop. ha ha ha

Not just the outer zones but the center is way overcooked, I estimate 6 or 7 times overcorrected.



#160 dogbiscuit

dogbiscuit

    Surveyor 1

  • *****
  • Posts: 1,943
  • Joined: 18 Oct 2018
  • Loc: Barksdale

Posted Yesterday, 08:29 PM

Using a full size lap, I don't know what can be done. A small sub-diameter lap can be used over the "kink" to prevent it going out all the way. Maybe as suggested, it is "unrecoverable" by his method, and he needs to return it to a sphere and start over.

Wrote this reply up about two weeks ago but didn't post because seemed Pete went missing.

 

 

Can't say I have experience backing out of a hyperbola that well developed. 5 or 10% over maybe, but never that hyperbolic.

Short strokes 1/3D or less near center COC or narrow W will work toward oblate and that's what I would use to remove correction. Have to push any crest near the edge off the edge. Might take a little while.

 

This far hyperbolic a petal lap like would be used to make convex hyperbola (or concave oblate) might be the thing to get the job done quickly, back to the other side of a parabola. Max pitch at the 71% zone decreasing from there toward the lap's center and edge. Might even work fairly smoothly without much tde developing.

 

Accented pressure works but I've become reluctant to suggest.



#161 pjmulka

pjmulka

    Viking 1

  • *****
  • topic starter
  • Posts: 996
  • Joined: 17 Sep 2015

Posted Yesterday, 08:59 PM

Wrote this reply up about two weeks ago but didn't post because seemed Pete went missing.


Can't say I have experience backing out of a hyperbola that well developed. 5 or 10% over maybe, but never that hyperbolic.
Short strokes 1/3D or less near center COC or narrow W will work toward oblate and that's what I would use to remove correction. Have to push any crest near the edge off the edge. Might take a little while.

This far hyperbolic a petal lap like would be used to make convex hyperbola (or concave oblate) might be the thing to get the job done quickly, back to the other side of a parabola. Max pitch at the 71% zone decreasing from there toward the lap's center and edge. Might even work fairly smoothly without much tde developing.

Accented pressure works but I've become reluctant to suggest.

Yeah, this kidney stone is kicking my butt!!! I’ve been out of commission for weeks

#162 pjmulka

pjmulka

    Viking 1

  • *****
  • topic starter
  • Posts: 996
  • Joined: 17 Sep 2015

Posted Yesterday, 09:02 PM

ok center looks cool [a little rough but figure 8's would get rid of that]

 

its the kink

 

now this is where you do the ToT edge from just inside the ink to outside the kink turning backwards, not all the way to the edge.

 

only 20mins and test.

 

all you need to do and look at is outside RoC.  outside RoC and hill is a hill and a hole is a hole.

 

you have a turned up edge now.

Okay so would the start position for this look more like A or B?

Attached Thumbnails

  • 1A2CA902-A61B-4894-8C48-D0B4B3BCED5A.jpeg
  • FFF11DEC-703B-47EB-A889-FAD2E3037466.jpeg


#163 Pinbout

Pinbout

    ISS

  • *****
  • Posts: 26,490
  • Joined: 22 Feb 2010

Posted Yesterday, 10:09 PM

Okay so would the start position for this look more like A or B?

Neither, but never A, never take the center of the lap past the edge of the mirror. Ever 


  • Knight Sky likes this

#164 dogbiscuit

dogbiscuit

    Surveyor 1

  • *****
  • Posts: 1,943
  • Joined: 18 Oct 2018
  • Loc: Barksdale

Posted Yesterday, 10:49 PM

Neither, but never A, never take the center of the lap past the edge of the mirror. Ever 

I do that sometimes. Not exactly as shown in the picture.
I draw the front edge of the lap past center to the rear supporting the rear overhang a little with one hand and apply a little pressure to the front edge with the other as I stroke the lap's edge from there forward through center.  Can remove trenches or dimples or buttons in the center, or just add correction to very center with less risk of trenches or dimples. Center area is small so doesn't take much stroking to do things there.



#165 pjmulka

pjmulka

    Viking 1

  • *****
  • topic starter
  • Posts: 996
  • Joined: 17 Sep 2015

Posted Yesterday, 11:17 PM

Okay so I’m not sure what to do next

#166 Pinbout

Pinbout

    ISS

  • *****
  • Posts: 26,490
  • Joined: 22 Feb 2010

Posted Today, 08:54 AM

Okay so I’m not sure what to do next

just wait... i'll show you.



#167 Pinbout

Pinbout

    ISS

  • *****
  • Posts: 26,490
  • Joined: 22 Feb 2010

Posted Today, 08:55 AM

I do that sometimes. Not exactly as shown in the picture.
I draw the front edge of the lap past center to the rear supporting the rear overhang a little with one hand and apply a little pressure to the front edge with the other as I stroke the lap's edge from there forward through center.  Can remove trenches or dimples or buttons in the center, or just add correction to very center with less risk of trenches or dimples. Center area is small so doesn't take much stroking to do things there.

if i have a small but bad turn up edge, I'll take the center almost out to the edge, but never cross it, while support the edges of the lap, so no weight will influence the stroke.




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics