Homemade Eyepieces

[nmoushon]

So I was looking online to try and see if I could find some guides as to how to design and make your own eyepieces. All the ones I found where very rough and cheap alternative eyepieces. Using pvc pipe and old film container style of DIY. Since I have access to a very good metal and wood shop I thought it could be fun to make my own high quality EP. Does anyone know of any books or articles that show you down to design different EPs and how to construct them? I was not very successful with my google searching, though it was only during lunch so I will search some more later after work. But thought I'd ask around and see of anyone knew of any. Thanks.

[Ruud]

The easiest to make is probably the symmetric design. It's a Plössl like eyepiece.

See this chart by Chris Lord. Zoom in deeply.

Lord-Eyepiece-Evolution-Tree.PDF

The two identical doublets need to be nearly touching for best results, I believe.

I have a book Telescope Optics, Evaluation and Design, by Rutten and Venrooij, that devotes a chapter to eyepieces. Also, read everything else by Chris Lord  at brayebrookobservatory.org

Good luck. Let us know how you fare.

[nmoushon]

Thank you Ruud. I will look into those books. Right now it's just a thought but I do think it could be fun.

[Ruud]

You're welcome. I just noticed that the pdf won't open in my browser (Opera - it says  "page crashed"), but it downloads just fine.

[Dave In Vermont]

I enjoy this chart. Have it hanging on my wall:

Feel free to copy and print if you like. I'll be snagging yours, Ruud.

Away -

Dave

[NEM]

Dave,

Which side of the diagrams should the eye be?  And in the chart at the bottom right, I assume the Y axis is refractive index, but what is the X axis?

Noel

[Dave In Vermont]

It should be customary, which is the eye would be on the left-side. But I've noted many of these are reversed. So while they are good as far as how many elements there are and how they are in relation to each other, I wouldn't use this as a builder's guide. Just to show how many types there are, and the many, many variants possible.

Regards the x & y - I don't know. Haven't studied that-yet. More fun for later!

Looks like TeleVue could be busy for centuries,

Dave

[Astrobits]

Dave's chart shows only a selection of  eyepiece designs, I have a list of about 80 designs and variants and even that is not the lot.

By convention the eye is normally on the right of the diagram as ray tracing is usually left to right but in Dave's chart the eye is on the left.

The glass chart in the corner plots refractive index against dispersion.

Nigel

[nmoushon]

Thank you again Ruud and Dave for the charts those are great. I will definitely try and find some more books on the subjects. Especially to learn as to which design is best for which circumstance and how to design and build them. 

I thought it would be fun to try and make the lenses themselves but seeing the bottom right graph on dave's really shows how crazy the angles are....might rethink that for complicated lenses lol.

[Stub Mandrel]

According to that my home made 'Plossl' is actually a Brandon.

[Dave In Vermont]

This may be the way TeleVue got started - some person tried to follow a backward-chart and wound up with something never tried before.

Calling Mr. Nagler.....

Dave

[FraserClarke]

X axis of the chart is the Abbe number, which as Nigel says is a measure of dispersion. Low Abbe number corresponds to higher dispersion. Combining glasses with high and low dispersion is how you achieve chromatic correction in lenses.   Unfortunately glass isn't evenly distributed across this diagram, so you don't have infinite choice in the combinations... There is a general (negative) correlation between Abbe number and refractive index.

[Peter Drew]

Making basic eyepieces such as Huygenian, Ramsden, Kellner and Plossl is quite straightforward, making anything much more sophisticated is going to be limited by the availability of suitable lenses.