6 replies to this topic

[Dale Eason]

I thought I knew how to use PLOP but now when I try to see where it would place points on a 3 point cell it does not show any dimensions it says there are no parts and thus shows no dimensions.  Anyone know how to make it work?

[Arjan]

Radius is somewhere around 40% usually, for 3 pt cells.

[davidlewis]

There are no parts in a 3 point cell because the 3 primary supports directly support the mirror. Parts refers to bars and triangles, which are only used in larger cells.

 

As Arjan says, around 40% radius is typical, but is non critical. Plop optimizes support only considering mirror deformation, which gives this number. However mechanical rigidity might cause you to want a larger radius.

[Dale Eason]

There are no parts in a 3 point cell because the 3 primary supports directly support the mirror. Parts refers to bars and triangles, which are only used in larger cells.

 

As Arjan says, around 40% radius is typical, but is non critical. Plop optimizes support only considering mirror deformation, which gives this number. However mechanical rigidity might cause you to want a larger radius.

Thank you.  So what you are saying is the contour maps and color maps and other metrics are based on that 40% radius.  

[davidlewis]

Thank you.  So what you are saying is the contour maps and color maps and other metrics are based on that 40% radius.  

They are based on whatever radius and design you are modeling. If you are choosing to use an 80% radius, it will show that. If you are optimizing the cell and it goes to 40% then it shows that.

[Dale Eason]

They are based on whatever radius and design you are modeling. If you are choosing to use an 80% radius, it will show that. If you are optimizing the cell and it goes to 40% then it shows that.

I got lost.  Where to you choose the radius.

 

Never mind I found it and figured out what I was doing wrong.  I had only been using the automated option.

Edited by Dale Eason, 25 May 2025 - 10:34 PM.

[Dale Eason]

I wanted to add thank you David Lewis for that program.  I have used it many years ago for several telescopes.  At one time I even used the interferometer and my DFTFringe program to monitor a mirror in the mirror cell and added a little extra force on one of the support points by making it taller than the rest and then watched the simulated results from PLOP agree with the actual deformation.