150mm refractor diy

Does anyone have some links to do it yourself projects for refractors?
I want better than f/5


Thanks

..::SuperBLUE::. wrote:
Does anyone have some links to do it yourself projects for refractors?
I want better than f/5


Better???


Thanks

What type APO or Acho? APO can go fast with little or no color. Achro
you need a high F#, long scope to remove color. D&G makes very good
Achros, and TMB, Astreya sells lens with cell APO's. Edmonds has some
books. Theres a group rainpipe telescopes has some baffel plans for
your tube design. You will need to make your tube to the lens.

Jim

..::SuperBLUE::. wrote:
Does anyone have some links to do it yourself projects for
refractors?
I want better than f/5


Thanks

I want the ability of terrestrial viewing, to take photos with a dslr, good
color, filters,...
f /2.8 or f/4 is ok.

".::SuperBLUE::." wrote in message
...
I want the ability of terrestrial viewing, to take photos with a dslr, good
color, filters,...
f /2.8 or f/4 is ok.

That's not a telescope, that's a camera lens. :-)

I assume that you're interested in a short FL lens for daylight viewing.
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'll note that the faster the lens, the more difficult the job is to do so
without excess color aberration.. The violet end of the color spectrum is
the worst end so you will probably be using a violet minus filter at all
times. 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.
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.

--
Why isn't there an Ozone Hole at the NORTH Pole?

A little glibly said, but true nonetheless.

To the original poster, no astronomical telescope is designed for terrestrial
photography with an f/2.8 to f/4 ratio. You really need to find a camera lens
for that set of requirements.

--
Sincerely,
--- Dave
----------------------------------------------------------------------
It don't mean a thing
unless it has that certain "je ne sais quoi"
Duke Ellington
----------------------------------------------------------------------

"Stephen Paul" wrote in message
...

".::SuperBLUE::." wrote in message
...
I want the ability of terrestrial viewing, to take photos with a dslr, good
color, filters,...
f /2.8 or f/4 is ok.

That's not a telescope, that's a camera lens. :-)

"David Nakamoto" wrote in message
news:FLIZd.8113$oa6.4977@trnddc07...
A little glibly said, but true nonetheless.

To the original poster, no astronomical telescope is designed for
terrestrial photography with an f/2.8 to f/4 ratio. You really need to
find a camera lens for that set of requirements.
And be prepared for the price.
Getting good correction wth such a fast lens, is a lot of work. If you
look at the Canon EF300 F2.8 (only 108mm aperture), you are looking at an
excellent lens, but a price tag, around $5000. Going down to F/4, brings
the cost down significantly, because for a given focal length the lenses
are smaller, and thinner. Nikon for example, do a 300mm F/4 for about
$1000. However if you want 150mm aperture, you are looking at a lens that
will cost in the order of perhaps $10000, and would cost this much to
make, in a version that shows low aberrations...

Best Wishes

"David Nakamoto" wrote:

A little glibly said, but true nonetheless.

To the original poster, no astronomical telescope is designed for terrestrial
photography with an f/2.8 to f/4 ratio. You really need to find a camera lens
for that set of requirements.

A quick search for 600mm f/4 shows a few around the $8000 mark, 400mm
f/2.8 lenses are similar in price.


Tim
--
I was not a helicopter.

..::SuperBLUE::. wrote:
I want the ability of terrestrial viewing, to take photos with a
dslr, good
color, filters,...
f /2.8 or f/4 is ok.

Bare minimum for what you want is a quadruplet. One CaF2 element, one
ED, and two normal glasses should put you within striking range of your
target. Raw materials alone will run a few thousand. Something a little
less expensive you may want to try is a F5ish newtonian hypergraph with
a well designed corrector/focal reducer to bring you to F3. You could
make something like this yourself without too much dificulty.

Ian Anderson
www.customopticalsystems.com