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Making a 33 cm f/4.8 mirror on the Mirror-o-Matic 6: polishing the surface with a pitch lap 

Jan van Gastel's video's
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After 'super fine' grinding, I moved on to polishing the mirror surface, with cerium oxide. I also tested with Ronchi and Foucault tester for sphericity and quality of the mirror's edge. No hooks on the end of the Ronchi lines and bright diffraction bands on both sides of the Foucault image: so no TDE

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11 сен 2024

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Комментарии : 29   
@janvangastel6763
@janvangastel6763 3 года назад
Yes, it is perfectly possible to use glass used for windows (it's named float glass). It needs to be thick enough though, so not thinner then other kinds of glass used for mirror making.
@satyajitbhadraroy7723
@satyajitbhadraroy7723 2 года назад
What is the thickness of this glass?
@janvangastel6763
@janvangastel6763 2 года назад
@@satyajitbhadraroy7723 25 millimeters.
@johncondoleobat
@johncondoleobat 10 месяцев назад
That’s a lost art of conventional polishing they want too do in now on c n c good job nice test !
@shaunsprogress
@shaunsprogress 4 года назад
My ears! how would you go about parabolising this sphere after?
@mohammedasif6322
@mohammedasif6322 3 года назад
Can we use plain glass like used for windows to make telescope mirror?
@nikosorf4250
@nikosorf4250 3 года назад
as long as it's not tempered glass and is thick enough it should be fine
@tikitak9190
@tikitak9190 3 года назад
Вращение электро-приводом верхнего диска ускорит процесс?!
@oleggerashchenko2201
@oleggerashchenko2201 3 месяца назад
Total length of stroke is 4 cm ( or 2 cm ) via excenter ? This critical??? Thanks!
@janvangastel6763
@janvangastel6763 3 месяца назад
No, stroke length is 2 cm. This is not critical at all. Might also be 3 cm or something like that.
@oleggerashchenko2201
@oleggerashchenko2201 25 дней назад
@@janvangastel6763 Thanks! What speed do you usually use for the table and eccentric during polishing? A good sphere is made.
@yobb89
@yobb89 10 месяцев назад
don't you want a parabolic figure when making a fast mirror ? , if so how do you flaten the outside edge of the mirror and how do you work out how much ?
@janvangastel6763
@janvangastel6763 10 месяцев назад
Yes, after polishing the mirror needs to be parabolized. I have also a video about how I do that.
@AliKhan-1966
@AliKhan-1966 11 месяцев назад
Nice
@tompolk7588
@tompolk7588 6 лет назад
Thanks for posting these videos! Does the AL polisher tool have a radius or flat surface before pitch lap?Are the Ronchi images inside or outside of ROC? Looking forward to your figuring videos.
@janvangastel6763
@janvangastel6763 6 лет назад
Hi Tom, I have AL tools ranging from 100 - 250 millimeters (every 10 mm). Up to 150 mm I left the surface flat, for larger tools I added a radius made of 2-component epoxy. I think the radii range from ~f/5 - ~f/7. I made them on a mirror I was working on when using the tool for the first time. The Ronchi's are outside of ROC
@janvangastel6763
@janvangastel6763 4 года назад
This is how I parabolized this mirror: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-LCi0BDmLSL0.html
@speedx5803
@speedx5803 Год назад
Nice job, beautful mirror! did you do any manual correction or you just finish the poslishing all in the powered turn table? I'm working on my first mirror and find that turn table poslihing like you show here always ends up with a lower center cave.
@janvangastel6763
@janvangastel6763 Год назад
I never correct by hand during polishing. The only thing I do by hand is removing astigmatism if necessary. I also have a central hole sometimes after polishing, but I don't care, as long as it is not deeper then it will be after parabolizing. In the early stages of parabolizing, the hole vanishes. Only for an f/7 mirror of longer it can be a problem and should be removed before parabolizing. I do that - on the machine - with a 75% tool, center over center stroke, with 15% overhang.
@speedx5803
@speedx5803 Год назад
@@janvangastel6763 When removing the central hole your way, will the curve change? notice you do it with 75% tool and 15% overhang, does the magic also work here that will keep the curve not changed? I'm asking because my goal is to make a optic spherical mirror. BTW, thank you very much for the quick reply, it is very helpful answer!
@PeterK6502
@PeterK6502 11 месяцев назад
The visible zones are likely similar in size to your used pitch square size.
@janvangastel6763
@janvangastel6763 11 месяцев назад
Yes, that's is right.
@materialsluckpr3384
@materialsluckpr3384 3 года назад
what ceriumoxide you are working ? white or red ?
@janvangastel6763
@janvangastel6763 3 года назад
Red.
@hpktech7736
@hpktech7736 7 месяцев назад
hi sir good
@sssskkkk3240
@sssskkkk3240 3 года назад
Please jan i need one 😕
@janvangastel6763
@janvangastel6763 3 года назад
No, I can't. I don't make mirrors commercially.
@sssskkkk3240
@sssskkkk3240 3 года назад
Hi jan Can you sell me one?
@metingokbulut837
@metingokbulut837 Год назад
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