16 inch F4 Primary


The 16 inch F4 Primary is home made from 25mm Schott Borofloat. The blank disc was supplied by J.B. Treasure in Liverpool who do a very good service.

Two of the optics are in the process of being made. One for the 16 inch F4 Run off roof, and one for Ian Baker's Observatory to replace his Orion 12 inch F4.


16 inch F4 Optical design


A link to Ian's wiki that has some conceptual designs: http://scopes.wikispaces.com/16+f3+Catadioptric

The optical configuration choosen is a folded design to keep the instrument compact with low wind loading to operate in the open air.

The secondary is 122mm in diameter with the baffle 130mm in diameter.

The camera is placed near the middle of the tube and is mounted in a bespoke focuser.

16F4_optical_layout_001.jpg


(From Ian) Hi Dave,

I have finished doing the support analysis for both the 18 and 9 point support. I have attached the final two spreadsheets and the two ANSYS plots.

The geometry given in the spreadsheets is the starting point for the FE analysis. The geometry is then optimised for both the 9 and the 18 point options.

The Support Radii are

9 Point:
Ro = 57.7mm
Ri = 163mm

18 Point:
Ro = 165.5mm
Ri = 71.7mm

Summary is .... You can support the mirror on 9 points no problem... ~60nm on the wave front... lambda/10
but 18 points gives you ~10nm on the wave front... lambda/60...

I reckon 18 point support is the way to go like you said... The lateral support can be posts located at 45 degrees. This should work fine or a strap if you prefer... I think I will go for the simplicity of posts. Provided they are free to roll then they should be fine. I will simulate this too :-)

16_inch_F4_MirrorSupportDeflection_9_POINT.pdf

16_inch_F4_Primary_9point_0019.jpg

16_inch_F4_MirrorSupportDeflection_18POINT.pdf

16_inch_F4_Primary_18point_0019.jpg#

Plop mirror cell design and parts below:-

16F4_mirror_plop_01.jpg
16F4_mirror_plop_02.jpg
16F4_mirror_plop_03.jpg