6 replies to this topic

[wells_c]

Huygens Optics just put out a YouTube video where he makes blanks from a Ceran glass cooktop, thermally treats them to have close to zero thermal expansion, polishes a parabolic primary and flat secondary, and configured them on his benchtop as a Newtonian telescope.

[Jon Isaacs]

 

Thanks

 

Jon

[rainycityastro]

I was just going to post. Such a cool bunch of info.
I especially enjoyed the parts about parabolizing techniques and reasons for the strokes. It wasn’t explained so well to me ever before.

Edited by rainycityastro, 23 June 2025 - 09:08 PM.

[wells_c]

Agreed, and there’s a teaser at the end so there will be a follow-up. I wondered if he would eventually cover something relevant to ATM, and he didn’t disappoint. He’s been dancing around it for a while

[GDAstrola]

That is a fantastic video to watch and thank you for bringing it to my attention.

[David L]

From the sound of it, he said that it would likely have been better to not do the thermal treatment.  Wondering if bigger piece of Ceran could be slumped and made into a meniscus mirror.

[wells_c]

I missed that part. In a prior video he extensively covers the thermal process he uses and the science behind it. To oversimplify, the material grows crystals within the amorphous matrix and the more crystal centers there are, the further negative the CTE goes (I have a 50 percent chance of getting that right from memory) In any case the temperature range where this occurs is below the point where it could be slumped, but it may be possible to slump it, cool it, then bring it back up… I’m probably going to watch that one again. One highlight is seeing him heat coupons of low-CTE material until they are red-orange, then dunking them into a glass of water, at which point the material made it clear that it could care less that it was undergoing massive temperature changes and didn’t understand what all the fuss was about.