Telescope Reviews: 6" F/15 Refractor Project

In this thread I will show my journey through making a 6" F/15 achromatic refractor. I am a physics/math undergrad at Louisiana State University and I decided to make my own telescope as my senior research project. I am hoping to get some great planetary views once the project is complete.

I started the initial planning of the project around January 2008. I bought the book "Making A Refractor Telescope" by Norman Remer and read it about 5 times. The book suggested that I make a 4" mirror as a preliminary project if I did not have any experience in grinding and polishing glass. So that is exactly what I did. I tried to make all of my mistakes and learn the process from the 4" mirror. Around this time I also started to get my lens making tools. The most important tools are a wedge tester, center thickness tester and spherometer. I ended up making 4 different spherometers. I will include pictures of them later. I was able to convert my wedge tester into a center thinkness tester. I will also show pictures of this later.

As for coming up with a lens design, I had a lot of help from Mike Jones and Dick Parker. I would like to thank them for all of their help thus far. I initially came up with a design myself and got a quote from GlassFab. The quote ended up being close to $1200. That was a little steep. So I ended up buying the F/15 airspaced doublet kit from Newport Glass for $550. This included the two lenses as well as a plate glass tool for each surface. I ordered the lenses in April and didn't receive them until June 23.

I decided to make a Baker type achromat. This design has the two inner radii (R2 and R3) the same. Dick Parker has done this with the Newport kit as well. There is a nice video on Stellafane where Mr. Parker goes over a lot on making an achromatic refractor.

The lenses come with pregenerated curves to a specific design chosen by Newport. I had Mike Jones design an equal internal radii achromat where the radii were close to the pregenerated curves done by Newport.

I worked most of the summer grinding with 220 carbo trying to get to the correct radii. I will give more details about my endeavour later.

I am currently at the polishing stage and hope to be done within the next month.

I will also talk about my Richard Berry refractor mount and my experience in getting the physics machine shop to machine my lens cell, tube adapter, and focuser back plate. I will include many pictures along the way.

Thanks for reading my intro.

James

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James
Canon XTi
Canon EF 200mm f/2.8L II Camera Lens
Celestar 8
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