Re: 150mm refractor diy

From: .::SuperBLUE::. (superblue_at_dontusefakkevip.hr)
Date: 03/16/05 

Date: Wed, 16 Mar 2005 15:12:54 +0100

> You will be wanting to obtain a free copy of OSLO-LT from Sinclair Optics
> and then learn the program and design a 4 (probably enough elements)
element
> lens.
I have an optalix demo www.optenso.de but I will try to use this too.

> I'll note that the faster the lens, the more difficult the job is to do so
> without excess color aberration..
Why?

The violet end of the color spectrum is
> the worst end so you will probably be using a violet minus filter at all
> times.
UV filter, right?

You'll also be spending a fair bit of money on some of the glass
> types that will be needed in that lens as you will need to reduce the
color
> as much as possible in the lens.
I am looking at BK7 170mm diameter lens from China, www.lzos.ru options,
Schott glass for grinding :(
What is the price of a glass like ED glass and where can I find thicks round
blanks or finished ones?
Smaller elements are not a problem (Edmund Scientific,... )

> One thing that you do have going for you is that film won't respond to a
> spot size of less than about 1/2 of a thousandth of an inch as that is
about
> the grain size. Asttonomical telescopes are usually done to diffraction
> limited level as we are very interested in getting the best resolution
> performance from the lens which is why so many telescopes are done as
> reflectors instead - there is no color with a fully reflective telescope.
> It is also a lot cheaper to build a reflective telescope as the glass is a
> lot cheaper than optically pure glass is.
So you are saying that I can end up with a monochromatic one? That is not
the intention.
I have noticed a few things on froogle from Scopetronix, but those are not
for refractors :(

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