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lithrow 5.8 inch f-15

Started by Phil Barker, 03/01/2013 04:26PM
Posted 03/01/2013 04:26PM Opening Post
I'm currently in the process of grinding a 5.8 inch f-15 lithrow lens

interesting history re this project it was going to be made by the late Garry Nankivell a famous professional telescope maker here in New Zealand for the late Harry Williams who also died a few years back well into his 90's.

It had been worked out using Zemax and I have the documents about it
Crown R1=895mm ROC R2=895mm ROC 17.145mm central thickness
Flint R3=895mm ROC R4=38500mm ROC 10.15 central thickness

Well crown is up to 280 grit and Saggitas within .05mm of desired mark.

I'm making R1 with seperate tool which is then turned to R2

R3 has its own tile tool as does R4 basically the flat back of a pyrex mirror I figured and havent coated yet.

All going along nicely I have a very good edge/centre thickness tester and spherometer I made myself.

Edge thickness is within around 1/100th of 1mm on the crown under desired accuracy.

I am making this because of the history of the blanks not to mention the very reasonably cost incurred. I am aware the lithrow will throw up ghost images and noticed on the inside of one of the blanks it had cementable?
Now I've dribbled on a bit sorry about that here is the question.

Can I cement this lens without it negatively affecting the images.

thanks in advance

Phil Barker

Posted 03/01/2013 11:16PM #1
Yes, Phil you can. I have a 4.5 inch f-15 Lithrow made by Garry Nankivell and in the lens case it has written "cemented Lithrow lens with excellent figure".

Peter Wilde in Palmerston North has Gary's Zemax files of lenses that he has designed and build.